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the mad stash: overwintering tender plants, a q&a with ken druse

IT’S THAT TIME AGAIN, or almost. Startling as it may seem, the mad stash is looming as fall takes tighter hold, meaning time to figure out where which of those gorgeous but tender plants you couldn’t resist at the garden center this spring can possibly be overwintered to live to grow again another season.

I’ve asked garden writer, photographer and longtime friend Ken Druse of KenDruse dot com to help me answer all your Urgent Garden Questions about overwintering tactics, which is the  topic of this month’s Q&A on my public-radio show and podcast. In a regular segment plus an overtime bonus 15 minutes, we covered lots of plants, from figs and rosemary to cannas and callas and dahlias and elephant ears, to potted trees (including citrus) and shrubs and more. After each brief discussion of a plant, I’ve also included a link to more comprehensive how-to about caring for it in the offseason.

Read along as you listen to the Oct. 2, 2017 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on iTunes or Stitcher (and browse my archive of podcasts here).

overwintering tender plants: basic strategies

(and fungus gnats)

 

 

Q.  You got lots of answers? You got all the answers?

Ken. Are you tender, Margaret?

Q. Yes, I’m very tender. But you do have all the answers, right? OK, good [laughter].

Ken. I have a question for you right off the bat. What’s tender; what do you mean by tender?

Q. Well, not hardy outdoors over the winter, wherever you shall garden. I think non-hardy, right? Can’t live outside?

Ken. Yes, so these are perennials that you can’t leave over winter outdoors because they will freeze and die.

Q. They might be perennial in Peru, right. We got a bumper crop of questions this time, especially from Facebook, thank you all at facebook dot com slash awaytogarden. We got questions ranging from figs to cannas, dahlias, rosemary, elephant ears, citrus, more, more, more, more, more.

But first, Ken strategically—don’t you think we have to talk strategy first, because I mean my places in my house or barn or shed that I might figure out to use to store things aren’t identical to yours, right? Let alone someone somewhere in another region.

Ken. Well, you never have enough places, and they’re never exactly the right places. We know the first thing we do is we’ve got those vacationing houseplants outdoors, and we bring them into the house and we put them in the sunniest windows or wherever we can, and they’re going to have to survive with the temperatures that we like. But, you know, that’s not all that many plants that want the temperatures that we have.

Q. Right, that really like it. And really, what plants like, whether it’s in the growing season or when they’re being overwintered or whatever, what plants like is a combination of humidity, temperature, light, and then soil moisture, right? It’s an equation. We’re trying to figure out a simulation, a mix of those four elements that if you’re totally dormant, it’s probably totally dry and the humidity—as long as you’re not rotting and it’s not 100 percent humidity it’s probably fine, and the temperature is probably low but not frozen. We want to make a formula for each plant or group of plants. But I’ve killed a lot of things trying to do this, haven’t you?

Ken. Well, I’m temporarily dormant. You know, you’re making me think of something that we could all do to save energy in our homes and help our plants is drop that temperature in the evening because all the plants want that.

Q. Or have a room or two, if we have [heating] zones especially or if we can turn off some old-style radiators—whatever it is—if we can do something to make some room… Do you have anything like a sunroom or a mudroom?

Ken. Yes, I have a sunroom, and most of my plants go into the sunroom. The temperature’s pretty low in there and I keep them on the dry side, so they’re not dormant to the point of losing leaves because most of these are evergreen plants from other climates, but the temperature during the day is probably 60 and then it goes down to, at the lowest, 50. But the plants that really like it warm are the ones that aren’t here anymore.

Q. I see, because you can’t really provide that. You’re not really providing that [warmer spot] with good light as well, right?

Ken. And humidity. It’s so hard to keep the humidity in a home.

Q. Now, you don’t use a humidifier, or whatever, anything like that, or trays of pebbles, or do you have anything else going on like that?

Ken. Well, I have my hospital window, and that’s my window…

Q. Wait a minute, you have your what? [Laughter.]

Ken. My hospital window.

Q. Do you have a nurse’s uniform? I need to know the details.

Ken. Just the cap, no.

Q. OK, good, good, good, good.

Ken. So I could either serve Good Humor ice cream or be the nurse. The plants that I really have to look at just about every day, that need watering very day or something—and there’s metal trays at the bottom of this. It’s like a bay window, sort of it projects out, and it’s got a metal tray that actually has a heater under, you know, a heat mat, so it’s a little bit warm. It’s got pebbles and moisture and higher humidity.

That’s where either the most beautiful plants go—well, sort of—and the ones that need attention. It’s not enough light to start seeds, but most of these things that need to be maybe watered every day, and some begonias, things that need to be just watched. Because the other guys that are in the sunroom, they’re lucky if they get watered once a week because there’s hardly any room to walk around. Then in the spring they all go outside, and in the fall, a little bit too late, they all come inside.

Q. You said hospital, I had one question from Facebook from Linda L., and she says, “Do you have any secret to get rid of fungus gnats that develop on plants brought in for the winter?” She tried a layer of sand but that did not work, like a mulch of sand on the top of your pots. In your hospital window—would somebody who had fungus gnats be in the hospital?

Ken. We go for prevention here if it’s possible.

Q. OK, so how does that work?

Ken. If one has, if you have, fungus gnats—and those are those little things that are like fluttering around close to the soil, and if you look really close you might see these little tiny worms sort of creeping around. Fungus gnats eat decaying matter, and that’s a sign of over-watering. The way to get rid of fungus gnats is to let your plants dry out between watering.

Q. Back off between waterings, yes.

Ken. And if you’ve got a bad case, stop watering and watch the plant. If it’s something like an African violet, which are really prone to fungus gnats because they always have a humus-y, very organic matter in their mix, in their medium, so you want to let that plant dry out. You don’t want to kill it by drying it out too much, but they’re kind of succulent so you can let them dry out quite a bit, keep your eye on it, and dry it out and your fungus gnats will go away. Also, what I do is I have one of those yellow sticky cards sort of above all the plants in the window, and that thing gets covered with bugs, but the plants don’t.

Q. So you are luring them onto this sticky, it’s not flypaper but it’s like the groovy, more modern, greenhouse-y kind of version of flypaper, right? It’s sticky that way.

Ken. Sticky on both sides, and it’s yellow, and you try not to touch it but you always do. [Laughter.]

Q. Yes, and then it’s adhered to your shirt, and then that’s very attractive. [Laughter.]

Ken. Oh, my gosh. Or a plant leaf, and then that’s it, the plant leaf goes. It’s very sticky, and most of the insects are attracted to that yellow color, which in the old days we could have called it Kodak yellow but people don’t know what that is anymore. Or taxicab yellow, and people don’t know what that is anymore, so it’s yellow.

Q. I often refer to things that I overwinter as investment plants, you know, like in other words– in house plants they’re sort of investment plants in the sense that I use them to decorate outside as sort of “annual color” in the garden season, but then I enjoy them for their beauty indoors too, so they’re sort of an investment.

But what I mean is—again, going back to that tender thing that we talked about right at the beginning—the things that are not hardy like tropical, subtropical, the sort of lavish, almost irresistible things that we see in the garden center in spring. A lot of times they’re really expensive, but they make such a fabulous splash if you have them, and you want to adopt them but then uh-oh, what do you do with them at the end of the season?

I think of them as investment plants, as in: I’m going to get my money’s worth and more if I can figure out how to make this thing survive.

Just before we go sort of plant by plant, you just mentioned you have your sunroom, which is probably 10 degrees cooler than your house or so, right? And you have your hospital window. Just quickly tell me the other places that you have that you do some mad stashing, and I’ll tell you mine, and then we’ll go group by group through the plants.

Ken. Well, I have a basement. The basement is a little too dry and it’s not that cool. But under what used to be a breezeway and now is the first-floor powder room—a bathroom—that’s a space that doesn’t have any heat in it but it’s attached to the basement, so it’s kind of warm. I think at the lowest it goes down to about 20, but usually it doesn’t freeze in there.

I pack as many things in there as I can that are dormant, but they would be killed if they went below 20, and actually more like 30.

Some of these are evergreens and you keep them kind of dry, on the dry side. I check them like once a month, make sure they don’t totally dry, unless they’re overwintering bulbs, some things that lose their leaves completely, and I let them dry in their pods.

Q. We both have our Eucomis collection [above], and I guess that we could go plant by plant, but we both have our pineapple lily collection that goes in our cellars, I think, yes? Or that kind of a place.

Ken. Well, that goes in that cool, cold space because they’re hardy to about zone 7, actually, so they go in there and it’s not that cold. It would be the equivalent of a winter in zone 8, I suppose.

Q. So those are sort of your three primary storage places, right?

Ken. Yes.

Q.  OK, and I’m in zone 5b. I’m in a colder…

Ken. Yeeew!

Q. I know, I know; stop it. Everybody always says that. I can get cold, in the minus double digits for sure and then some, so I have an unheated garage but it’s very well insulated. I have that as one possibility, but I can’t guarantee that it’s going to be more than a couple of degrees above the outside temperature.

Then I have a basement that is probably about…it can be 35 or it can be 45, depending on the kind of winter we’re having, because there is a boiler down there but it’s not warm. It can be a little humid, not bone-dry.

Then I have indoors in the windowsills, of course. I actually have one of those Bilco doors, those exterior metal doors that you open up and go down a staircase into your basement, a bulkhead.

Ken. A bulkhead, right.

Q. And that’s another place., I’ve never used it, but I know people do use it for certain things that are sort of like that cold space you were talking about. Those are some of the places that I’m using, and then I also have a shed, it’s almost like a little cabin like maybe 12 by 9 or something, that I have a tiny little bit of baseboard heat so it sort of is at like 40 degrees and it’s got a little skylight. It’s not bright, but it’s not dark.

Those are my places, so I just thought … and just for a caveat for everybody: You’ve got to experiment, because again, even though Ken and I just described two cellars, our cellars are different. I mean, they’re not the same place. [More on the basics of overwintering at this link.]

into the cellar: cannas

Q. About stuff in the cellar, we have a question from Shelly on Facebook, Shelly D., and she says, “I bought some beautiful variegated canna lilies in the spring and want to store them for the winter.” This will be her first attempt.

To me, those are the easiest of the easy, and that’s a cellar thing. Is that cellar thing for you too?

Ken. Yes, that can actually go in the cellar that’s not that cold.

Q.  OK. That’s what I put in my regular basement, yes. Just above freezing.

Ken. Right, and in this case it’s about dry as more than about cold.

Q.  Right, and I let them get hit by frost, blackened by frost, unless no frost comes. But I like the sort of plants to get that trigger. If they’re going to go dormant, I like nature to tell it, “Hey, it’s time to go dormant,” and they do their kind of withering thing, if I can get that, then cut them down so that there’s not much stem left.

I usually put them in my garage or something for a couple of days just to dry them off a little bit. And then I just put them in bins or even in garbage bags, not closed though, but just sitting open in the cellar. Boom, and as long as it’s above freezing that’s what I do with them, and I have them a million years. I think those are super-easy.

cannas-with-snow

Ken. OK, this is the cannas you’re talking about. [Cannas getting frosted in an early snow, above.]

Q.  Yes, cannas.

Emily, also on Facebook, said she didn’t dig them up last year. She’s in a slightly warmer place, and she wanted to know how hardy they are. They came back up but they didn’t flower this year, which I don’t know if that has anything to do with her overwintering them. She wanted to know how hardy they are.

I actually had to look it up because I don’t know, I think you can get away in zone 6—excuse me, yes, warmer than zone 6—so zone 7 and warmer you can leave them in the ground, and some people cheat and mulch them a lot if they’re on the border of those temperatures. But yes, I mean, I have to dig them.

Ken. I think that one reason they might not have flowered is that they might have been killed back a bit.

Q. Too much, right? Not enough eyes [growing points]?

Ken. Yes, and she’s getting some of the smaller eyes are growing.

Q. Right. That makes sense. But those to me are the easiest, and I don’t even pack them in any kind of medium. I just kind of pile them up in big flower pots or, as I said, bins or the garbage bags that are left open.

into the cellar: calla lilies

Q. Now, callas, we had a couple questions about calla lilies [above right, ‘Fire Dancer’ calla], and I do those dark and dry also, same kind of thing, but I usually leave them in the pots just because…

Ken. Oh, I was going to ask you.

Q. Yes. You know, it’s just easier, and you can get a few years in the same pot usually.

Ken. You know, when they’re outside, sorry to interrupt you, but when they’re outside, I turn things like that, I turn the pots on their sides. While they’re still outside, I don’t want that medium to be wet when I get it.

Q. Good point, so the sort of staging [their gradual trip indoors], right? It’s not just bring it in soaking wet if you don’t have to.

Ken. Right, so I put the pots and the side and rain won’t go in. I try to get them in a sheltered place. If they still need light, they’ll get some light. Then when I bring them in they’re in the dry soil, because if they’re in wet soil and you bring them in, chances are they might rot.

Q.  Right, OK. That’s very, very good point. Similarly, I said I like to leave the cannas especially, I’ll take them out of the ground, and then I like to let them dry, let them cure for a few days in the open air, if I have a place, like in the garage or something.

into the cellar, but trickier: tuberous begonias and dahlias

Q. Tuberous begonias [above left, an apricot rose-form variety]?

Ken. Uh!

Q. I know, don’t have a nervous breakdown. To me, it’s also in the cellar—I only have one cellar, you know what I mean—but these are a little trickier, right?

Ken. Yes, or impossible, one of those.

Q. Yes, yes. Even the experts frequently say [laughter] the trick to doing really well with these and with overwintering them is grow them in pots, like little plastic nursery pots, and if you want to put them in beds or in a hanging basket, plunge the pot right in the basket or the bed and put mulch over it. Even expert bulb growers have told me that because it’s so easy to damage those succulent tubers when you dig them, and that’s where they rot. And where to put them, they want more like maybe 50-ish degrees, not your 20-something, right?

Dahlias also, again, I would have to put them in my cellar, but they’re a little trickier too, I think. Have you ever stored dahlias? [Above. antique dahlias from Old House Gardens.]

Ken. Yes. The canna thing that you described, that’s cannas. The dahlia thing, even though we think of them kind of together, I don’t do them like you were describing for the cannas. Sometimes I wrap them in newspaper, wrap them carefully like it’s a gift, and tape the newspaper kind of shut, and then I’ll sprinkle the newspaper with water through the winter. I’ve done them in sand. I’ve done them in peat moss. One time I did them in sawdust, and that worked really well. I’ve done them in dry leaves, chopped up oak leaves and stuff. All of those things actually have worked.

Q. Christine on Facebook also wanted to know the best way to protect the tubers that she had in storage during the winter from mice. I’m obsessed with mouse traps, so I would say the best non-toxic way is you’ve got to check your mousetraps in your storage area all the time and re-bait them all the time. I mean, when I say bait I mean peanut butter, not poison.

Ken. You know, I’ll bet what you could do if you were wrapping your dahlias and things like that, you could probably put them in a metal trashcan with the top closed, as long as you’ve wrapped them loosely and it’s not going to get too wet, just to protect them. What do you think about that?

Q. Yes, it’d have to have those holes in it, like one of those cans that’s meant for burning or something. It would have to have good ventilation, I think, not to get too funky inside.

Ken. Tiny holes.

Q. Yes, tiny holes, I guess.. But Kathy Tracey of Avant Gardens in Massachusetts—you know Kathy.

Ken. Sure.

Q. She says she does a lot of dahlias, and she told me when we spoke a couple years ago about this that she waits for the frost to blacken the foliage. That’s an important thing even more with the dahlias than it is with the cannas, to really let nature’s cue tell them, “Sleep, sleep, sleep,” and let them finish their cycle and wither.

I believe she said that at the place where then she cuts off the stem she sort of turns them upside-down a little bit, almost like hangs them upside-down, so that the excess moisture where that stem was cut kind of drips out. It doesn’t drip back in and rot the tuber. Some people use a fungicide and obviously you have to be really careful with that even if you’re using a “natural” one like a copper or sulfur one.

But curing them a little bit before storing them, like before you wrap them in your newspaper as you said—and she uses like wood shavings or peat moss, or she even just puts them in dry potting medium and puts them under a bench somewhere in that cool place. Then when it’s time next spring she’s already got them pre-potted, do you know what I mean? [Kathy Tracey’s method with dahlias and other tender plants she stores.]

Ken. Oh, wow, great to know.

Q. Yes, so that’s kind of skipping a step, not having to get them out of their storage and then pot them and start them early, so I thought that was kind of good. Yes, so many different things.

where to store elephant ears?

Q. Elephant ears; oh my goodness, elephant ears. These are trickier, and some of these I don’t put in the basement. The old-fashioned ones, you know, those giant ones with the sort of scalloped shiny green leaves, I think you could put them under the bed and they’d be OK [laughter], drive them around in your car, I don’t know. They seem tough, right?

Ken. Do you let them go yellow and just save the tuber, or do you keep them growing, the big ones?

Q. I mean, I would let them quiet down—like dry off, wouldn’t you?

Ken. Yes.

Q. Yes. But it’s been getting trickier. You know who has good instructions? Because there’s Colocasia and there’s Alocasia and there’s all kinds of different ones. Now there are the ones with that side of matte kind of purple-y leaves [like ‘Mojito,’ above], and the ones with shiny leaves. I mean, it’s….

Ken. Xanthosoma.

Q. Oh, I don’t even know what that is. Forget it. [Laughter.]

Ken. [Laughter.]

Q. But seriously, I mean, I think it was Tony Avent, at Plant Delights—he has a whole giant collection, and he’s friends with a number of the leading breeders, and all these new ones that they’re developing, he says that some of them, the newer varieties, they don’t form corms as quickly—you know, like a mother bulb, so to speak—as quickly as some of the old-timers. So there isn’t something under there to store, so leaving them in their pots and even keeping them growing is the approach with those. I’ve been experimenting with keeping that one called Amazonica, do you know that one? It kind of looks like an African mask; it’s a very brightly variegated one with a shiny leaf, very triangular, the leaf.

Ken. Oh, yes, yes.

Q. I’ve been keeping that growing in a cool place, watering it, growing, growing, growing. Now three, four years in, the bulb is getting of size where maybe I could store it. I’m not sure. I might just not press my luck and just keep growing it instead. It’s almost like a houseplant in my cool mudroom.

But Tony on the Plant Delights website has about the best explanation of what’s going on with how to figure out which kind yours is. Those [that form big corms] need to be dry, cool, and above freezing if you are storing them, or light and not too hot if you’re growing them on as a houseplant, I think. I don’t know. I mean, those are tricky.

Ken. I think the Alocasia in very general that we don’t let those go dormant. The Colocasia, most of those can go dormant, but some of them you grow outside in the summer in water, you plunge the pot halfway down into water and they like a lot of water. They like to almost grow in water. But then in the winter they don’t want to grow in water, and we bring them in and kind of treat them like limping-along houseplants. If you can keep them alive, then they come back kind of in the spring.

agapanthus: bright and cool?

Q. Which one shall we do now? How about the sort of in-your-sunroom kind of a place, or my mudroom.  Again it’s bright and slightly cooler than the house. Would you put Agapanthus in there? Cecilia on Facebook wants to know. She paid a lot of money, she said, for one; she bought one, and it was a pricey plant, and she wants to know where to overwinter it. [Above, Agapanthus bloom from Edoddridge on Wikimedia.]

Ken. I overwinter it. It doesn’t look good. It’s not happy. It’s alive. The best ones I’ve ever seen overwintered were in one of the Hamptons houses, right up against very, very bright windows, in a house where they turned the temperature down, way down during the week, or even over the weekend. But so much sunlight, more than I have, with giant windows facing a bay or something. They look just like they do outdoors, and then they start to bloom in the late spring, and they bloom for quite awhile. I think they want to be kept cool, but bright, bright, bright.

Q. You have an evergreen one, and that’s one of the things that Cecilia should know. There are evergreen and non-evergreen varieties.

Ken. I can’t tell. [Laughter.]

Q. She’s got to look it up according to the label on it. The evergreen ones are about zone 7b-ish, and they want that sort of simulation of a cool greenhouse, that I don’t really have. My mudroom’s the best place; it’s just like what you were just saying. But the ones that are easier for us Northerners, I think, are the non-evergreen ones. They have the less-thick leaves, and they’re going to go dormant, and those could go in the basement, with no light or water required.

Ken. Oh, I should try that.

Q.  Yes, so it’s kind of good searching those out for us Northern gardeners. We still have to talk about succulents and rosemary and stuff that you store in the garage, and all kinds of crazy stuff.

Ken. I have so many questions. [Laughter.]

Q. Oh, no, no, no, no. Now, be quiet. We were in the sunroom and we’d stored some agapanthus, or we’d put some evergreen agapanthus in there, and we’d shoved some non-evergreen ones in the cellar dormant.

overwintering tender succulents or citrus

Q. Do you store any succulents, non-hardy succulents, like Echeveria or Aeonium, or you know what I mean. Do you do any of those?

Ken. Yes.

Q. I do a terrible job with these. I have to say, I don’t have the right spot.

Ken. Yes. [Laughter.]

Q.  OK, good. [Laughter.] Yes, these are tricky, but sometimes you can do a good enough job to get good cuttings for next year, right?

Ken. Right. Well, sure, and keep them alive. They’re in there right with my citrus plants.

Q. Right, OK. So now…

Ken. Does that make you think of anything?

Q. That I want to simulate California situations?

Ken. Well, we could mention this because…

Q. Winter in California, I mean.

Ken. I think that you got a question about citrus, I believe.

Q. Yes. I’ll have to find it here in my crazy notes. It’s here somewhere.

Ken. Oh, you don’t have to, but I’ve got quite a few citrus. I love citrus. All my life I wanted to grow citrus. You know, everybody wants fruit in the winter in the house, and the wonderful fragrance of the flowers. I had plants that lived and lived and lived and never bloomed, but the sunroom, which I redid, it used to have windows that were high-energy, wonderful windows with coatings. I called it dead light because the plants were right in the window but looked like they were in some tiny bathroom window, and they just didn’t act like they were in the sun. So I redid it with windows that have no coatings, but that’s the sunroom’s…

Q. Like full spectrum-y kind of things?

Ken. Yes, and it’s all sealed off so it doesn’t cool the whole house. Or make it warm, actually, either. They bloom, starting usually in February. I’m looking at some fruits because fruits can sometimes take nine months, like a baby, or longer. I’ve got some Buddha’s hand and I always have finger limes. I love the finger limes. And Meyer lemon, that’s about the easiest and best, I think, indoor citrus of all. [More on how to overwinter citrus, with Four Winds Growers.]

Q. Citrus—and in that same room, again, simulating a California winter, you could try your succulents.

Ken. The succulents are in the brightest spot I possibly have, and I keep them kind of dry. They limp along. Sometimes they grow, and that’s not so good. Well, it depends on the succulents too, but you mentioned Echeveria. The echeveria, they’re alive in March, and then I take them outside and they’re a little bit better. But things like aloes, they’re fine, and agave even. Keep them really quiet and cool, and they’re OK, too. They just sleep, so they’re not as troublesome as what you happened to mention Echeveria.

Q. Sorry about that. The reason I said it was because of the other thing I said, which is you’re going to get this stretched-out thing. Suddenly it’s going to push up and stretch out, even if you haven’t watered it, even if it’s only like 45 degrees where you’re keeping it and it is as bright as you can provide. Then suddenly it’s going to stretch out and sort of flop over, and the pot will fall over [laughter] because it’s so top-heavy.

But the thing about that, and again, this was another Kathy Tracey tip from Avant Gardens [above, Kathy with one of her succulent pots]. She’s the succulent queen; she loves succulents and she’s been in her very cold climate in eastern Massachusetts. She’s been growing them and collecting them. She’s got one of the best collections in the Northeast certainly of non-hardy as well as hardy succulents.

She disassembles all these extravagant, big pots she does in her gorgeous garden and nursery. She puts them in small pots of very fast-draining potting soil, like a cactus and succulent mix. Pots them down, in other words, from her big urns, and brings them into like 35 to 40 degrees, but with tons of light, and hardly ever waters them—I mean, really, really, minimal watering. She said to me, “Yes, yes, the echeverias, they’re going to maybe look like hell. But cut off those tops, let them…” What do you call it when they kind of harden off, callus? Is that the word: callus?

Ken. Right, right, callus, exactly.

Q. Leave them out in an airy, dry place, and let them callus for a while, and then root them. It’ll take a long time but you’re going to have the next generation. She was right, of course, because she’s an expert. [Laughter.] Yes, so those can take cool. Again, we’re trying to pretend we’re in California in the winter. That’s what we’re simulating, which is dry, cool, and bright, yes?

Ken. Yes.

overwintering rosemary in cold zones

Q. Dare I ask about rosemary? I’ve killed a lot of them.

Ken. Well, that’s a whole different thing. [Laughter.]

Q. I’ve killed a lot of rosemarys. Well, but I was thinking of your sunroom, because you told me the places you have and I told you the places I have.

Ken. No, I think it’s not cool enough.

Q.  I think you’re right, but your bulkhead, or whatever it is, in the dark isn’t going to do it. And your hospital window isn’t going to do it.

Ken. No, no, I don’t…

Q. That’s what I was saying. The sunroom is your closest thing, but it’s not cool enough, I think.

Ken. I think that’s it. Not cool enough.

Q. Jean on Facebook said she always tries to bring her rosemary in to winter on a windowsill. She’s in zone 5b. Then she says [laughter], what you and I are saying, “Only one has made it past March when it usually dries out and gives up.”

Ken. It dries, it dies.

Q. Yes. Yes, yes. I should say, I’ve given up, you know what I mean? I’ve given up [laughter]. Because they’re not too expensive to buy, really. I’ve given up, and I take the stems off and put them in a plastic freezer bag; I take all the branches off, put them in a freezer bag with the needles on, flatten it out, get all the air out, and freeze it, and I have rosemary to cook with forever and ever. That’s what I do with them, use them on roast potatoes and stuff like that. Isn’t that awful? But if you really wanted to overwinter them, and this was something I learned from … Do you know Nichols Garden Nursery, Rose Marie Nichols McGee? Have you ever met at flower shows or anything?

Ken. No, no.

Q. She’s been in the herb business and the seed business for ever and ever, and they’re out in the Pacific Northwest, but even there sometimes they can get cooler. She says, “If you have a rosemary in a pot, first of all, you want the hardiest rosemary you can get.” Not all rosemarys are created equal, especially if you’re in a cold zone. Anytime it’s in the 20s or below, it’s got to get sheltered. But if it’s not the 20s, like don’t bring it in too soon, and don’t keep it in too long. You know what I mean? If your weather stabilizes to 37 or whatever, get it out of the house. But it is, it wants very strong light and wants like 50 max; 50 at the most, but more like 40 would be better. It’s a really tricky one, guys, and I just don’t think people should feel bad about not, in the North, about not having a good spot for that. [Overwintering rosemary, indoors and out.]

Ken. Do you think that’s probably the same for Spanish lavender?

Q. Oh, I mean, I can’t even grow it. [Laughter.]

Ken. But people, they sell it and I’ve seen it at the box stores right next to the hardy lavenders, which is horrible. People buy them because they’re so pretty. I think it’s Lavandula stoechas or something like that, and they’re pretty and they bloom and they’re not hardy. Or you could move to Tuscany or the south of France.

Q. That’s a good idea. That’s a way to overwinter them.

Ken. Or Farmingdale, Long Island; you could do that.

Q. Let’s talk about some sort of, there were a number of questions. Hil in zone 7b asked about strawberry plants in a strawberry pot, and Coco asked—again, on Facebook—about Clematis in pots. She wants to know wants to know what to do with them.

Jean, who’s in I think zone 4, she put paperbark maple trees (Acer griseum) in pots. You know, I grow Japanese maples in big pots, and she wants to know what to do about them. They’re zone 5 plants, and she’s in zone 4, as I said.

And Leslie, she puts some evergreens—Japanese plum yew (Celphalotaxus) and some other things—in New Jersey in a pot.

People are saying, “What do I do with these things that are sort of hard or almost hardy?” To me, this is the sort of garage or your…

Ken. Oh, exactly.

Q. Or your whatever you call your cold place, right?

Ken. Well, yes. Your garage/barn/garage, that’s the place. Because then they’ll be out of the wind, and if they’re kind of dormant, pretty much dormant—if they drop their leaves, they’re not going to get burned by the wind and they’re going to be a little protected. But they’re going to be allowed to go down to… You know, if you’re in zone 4 it’ll feel like Zone 5 in there, or Zone 5 it’ll feel like Zone 6.

But when you mention the evergreen things, that’s a little trickier, I think.

Q. Right, because those can dry out too much, and they do have their leaves on, unlike these other things that are deciduous. They do have their leaves on, so they are not photosynthesizing at a wildly active rate, but they are accustomed to being in light. I put those—I have some columnar conifers, which you and I have talked about before—in pots  [above] that I like to use as accents in the garden seasonally. But I don’t want them to get all beat up, and besides the pots are clay and they’d explode outside. So I drag them into the garage, and again, an unheated garage, insulated but unheated. I put them by the two windows; that’s what gets the windows.

I don’t bother putting a Japanese maple or something else that’s leafless, even my figs — and we have to talk about figs quickly next—I don’t put deciduous things that are dormant near a window. I don’t give that precious cold, bright space. I give that to the conifers, if that makes sense. Yes?

Ken. Right, To the plum yew that you mentioned; something like that that’s evergreen. Some people think that the products that you can spray, the anti-desiccants, don’t work and it’s silly, and some people think that they do work, and frankly I think they kind of do work.

Q. Yes, that’s an interesting idea.

Ken.They keep the moisture and the needles and the leaves. I wouldn’t put it on something glaucous like your conifers, but for the plum yew and something with broader leaves, I might try that. But I think you’re covered with that, if you happen to build a garage with windows or have one.

Q. Right, but as far as the clematis in pots, I’m not worried about the clematis. It’s that it’s above ground in a pot and the root zone is therefore exposed, like a zone colder or so, and the pot’s probably going to bust. I’d put it in the garage, and I think those will do great. Same with that strawberry jar.

The paperbark maple, besides the fact that she’s in Zone 4 and it’s a Zone 5 plant [also sometimes listed as Zone 5], it’s a 25-foot tree so it’s not going to be too happy too long in a pot, even a very, very, very large pot, so that would be my thing there.

overwintering fig trees

Q. I want to race on before we run out of time because that’s one of the most common questions. Joey asked, “I’m in zone 5b, have a potted fig. I want to roll it into the garage. It’s just a baby of a couple of feet tall. What should I do, and do I water in the winter?” I always have asked Mr. Fig—I’ve got a couple of figs myself, and I asked Lee Reich years ago about this. [How to overwinter a potted fig, with Lee Reich.]

Ken. Uncommon fruits.

Q. Yes, “Uncommon Fruits Worthy of Attention” was his first book where we all got to know him, and he’s done many since. But, you know, I put mine in Zone 5b in this insulated garage, and they’re fine and they live and live and live, right? They don’t even get dieback. It can get to zero in there easily, right?

But Lee always reminds me that if it gets too big—he’s always like, “How much longer are you going to wheel that damn thing around?” He’s like, “Lay it down. Pull it out of the pot on a tarp, and cut off half the root ball. Root prune it because it needs it anyway to stay small in a pot.” And then drag it into your cellar, and put a plastic bag around so that all the root ball doesn’t fall apart, like wrap it up. Drag it into your cellar. He says you can even cut them back. Because after all, people have grown them in areas where the whole top of the plant isn’t entirely hardy, and pruned them hard.

Ken. He’s only wrapping the root ball?

Q. Yes, that’s what I mean, just so that it’s not a mess all over your basement floor. Put it in a plastic bag loosely tied, the root ball.

Ken. I didn’t want people to put the top growth in plastic bag.

Q. No, no. Just drag it into your cellar and let it be down there cold, and he says 20 degrees, 30 degrees, perfect, fine, whatever. But he keeps his in a 35-degree-ish space. There are many ways. They’re hardier than we think, and then of course there are some varieties that are hardier than others. Again, the variety that a person has is going to make a big difference.

We had more and more and more questions that we’re not going to get to, Ken.

Ken. Sorry.

Q.  But that’s OK. I’ll try to answer some of them, maybe you can jump in too, and we can answer some of them right on Facebook. The mad stash, it’s just ahead, Ken. Are you ready?

Ken. No, but am I ever? No.

more overwintering advice

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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its seventh year in March 2016. In 2016, the show won three silver medals for excellence from the Garden Writers Association. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the Oct. 2, 2017 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes or Stitcher (and browse my archive of podcasts here).

(Garden doodle of “The Hoarders” top of page by Andre Jordan.)

  1. Chris says:

    Geraniums (pelargoniums) are another easy-to-winter tender plant. I keep a few growing in pots in a very bright southern window; I’m always surprised at the amount of bloom I get. But after years of discarding most and buying afresh in spring (which adds up, I’ve a big terrace), last fall I shook the soil off most, dried them in the sun for a day, then stashed them in paper bags in a cold closet. They looked pretty sad come spring, but they were all alive. After heavy pruning and repotting, they’ve done beautifully. The price I paid was a real delay in summer display, three weeks at least. But a lot of money got saved for very little effort.

    Oh, something else: sweet potato vines make sizeable tubers, which store and regrow nicely. Again, there’s a delay.

  2. Elizabeth E. Brumbaugh says:

    Hi Margaret, would you have any tips for overwintering climbing plumbago growing in large urns? Zone 5b like you.

    1. margaret says:

      Such a nice plant — sort of old-fashioned. I did find one piece of advice from the former National Gardening Association Q&A archive, which is here, which confirms what I would think it would want. Missouri Botanical says you can even store it cool and dark, really forcing total dormancy I guess. But both sources says give it a serious haircut around the time you plan to bring it indoors.

  3. Alissa says:

    Ken’s comment about the window coatings is something that I have also noticed here in Wisconsin (zone 5b). I discovered that an east window in a bright southern room was the only way to get my rosemary to overwinter when I was in a building with coated windows. I think the early morning sunlight helped. I had successes many years in a row, then moved to a home with completely uncoated vintage windows, southern exposure, and now the rosemary actively grows in the winter! It still feels a bit like a miracle.

    1. Diane L. says:

      My friend had a rosemary plant in an improvised hoop type house. She left it out all winter and it must have been the micro climate that caused it to thrive. It came back the next spring/summer with robust growth and resembled a small bush. Very impressive! I may attempt this on a smaller scale with plastic supported by branches. I live in zone 6-ish.

  4. Sheri says:

    I’m down to one tender “Clivia Lily” that I still have to haul into the garden room. Hitting your 60’s also hits your knees and lower back. I swore years ago that I wouldn’t have these “tenders” but a dear neighbor who is now “gone” gave it to me….and it is so beautiful & sweet smelling in bloom.

    1. margaret says:

      Hi, Sheri. I confess some of my biggest Clivia never left the mudroom this spring for the great outdoors. They are heavy! : )

      1. Sheri says:

        LOL! That’s funny! I’m actually thinking about leaving the darn thing out and just throwing a garbage can over it, say a prayer and hope it makes it to Spring!

  5. Susan says:

    I’m in Zone 4, Rocky Mountains. I bring my Rosemary plants in when the temperatures are getting down in the mid-20’s at night, and after many years of dried up dead plants, I found one spot where they will reliably overwinter. It’s a very cool (about 45-50 degrees) enclosed north-facing entry with a big roof overhang, so it’s really quite dim light. I water them about every two weeks, and though there is some dieback, they have been overwintering pretty darned well for a number of years. Prostrate Rosemary has also been much hardier for me than the more upright forms, less dieback, and I love the droopy gnarly look.

    1. margaret says:

      Lucky you, Susan, to figure out just the spot. I think if my mudroom (or Ken’s sunroom) were more like 50 day and 40 night (versus 60-50) they’d be OK, too.

  6. Hi Margaret. I love all you write!!! I am still trying to grow Astillaboides Tabulares….two plants
    from White Flower Farm dead…replaced, also dead. Two from Annie’s in CA. lived through
    the summer….tenderly treated to a little mulch, liquid fertilizer and careful watering. Now
    it is October…still warm here in Maryland and no rain so more watering. All dead. Last Spring one came up after the winter but later died,. This is all in a north facing bed with daily sun
    nearly all day with trees overhead. Huge maples. This is a bed I carved out of a lawn with
    a rototiller and adding lots of top soil,etc. The hostas grow well here as well as the hydrangeas .Any ideas? I fell in love with this plant after seeing it in your garden.

    Thanks from Anne

  7. Yolanda Reyes says:

    Hey Margaret! I just have to say that when you talk about protecting your elephant ears, I cringe. Here in central Texas, they are invasive. They take over river banks and Master Naturalists like me spend many hours in the Texas heat removing them!

  8. CIndy Donahey says:

    I guess you can use old man’s beard, or sweet autumn clematis,strands for insulation in any number of ways. I used some for Halloween with a decent bat from the thrift store. You can dig pits of varying depths in dry places by buildings too. You have to put a gauge out now to check for rainfall accumulation. People used to swear by maple leaves and pine needles. They would have a layer of pine cones at the base of boxes. Back years ago, you did this yourself or paid. Some people held fires in the spring with this material. Have done very little myself, have not thought about this in decades.

  9. Ann says:

    In Michigan near Detroit my rosemary came back outside. I just figured it would have dried/died inside. I was so surprised. I did cut it back hard almost to the ground. I did not even cover it but it was a mild winter here and my parsley overwintered too. I also have a fig that did not bear fruit this year but this year I am splitting into two plants and cutting it back and I’ll over winter that in the garage. Do you both think the zone charts will change? Who determines that? I really love listening to You and Ken. I feel like I have found my people.

  10. Tibs says:

    I used my unheated attic to store cannas. Worked great until on winter we had a long period of cold. Lost them all. Plus carrying stuff up 2 flights of stairs and thru a bedroom made an awful mess. I have a northeast facing spare bedroom I put all the house plants in. Door is shut to keep cats out and register is closed. It gets down to 50s. I’m going to try to over winter an elephant ear in the pot in there.

  11. Pat says:

    Help!! There are tiny ants in my potted Meyer lemon, (in the soil and on the blossoms). How can I get rid of them? I want to bring the plant in, but not with ants. I’ve tried soapy water, but the ants are still there.
    PS The tree is full of lemons.

    1. Diane L. says:

      I’d try ant traps. If the ants like sugary type food sources, there’s a borax/sugar type DIY trap you can make. I take plastic lids and saturate a paper towel (or cotton balls) with the solution. The ants take the ‘food’ back to the queen and eventually they should die off. The recipe is:
      -1/2 cup sugar
      -1.5 tablespoons borax
      -1.5 cups warm water

  12. Diane L. says:

    Found the perfect large saucer for trees!
    I have a 40+ year old grapefruit tree that I summer outdoors and then schlep it back inside for the winter. It is in a very big black commercial type pot. The challenge is containing water drainage under the huge pot. I’ve used concrete mixing bins with some luck, but the plastic sometimes cracks and then I’ve damaged my oak floor.
    I finally found the perfect saucer! It’s 25 inches in diameter and made by Gro Pro. The plastic is substantial and thus far is doing well under the weight of the tree. It also is reasonably priced.

  13. I have a question; we overwinter our agapanthus in a sunny cool spot and they overwinter very well. They flower well too, but the flowers flop over. Anything we can do?They are the small leafed variety, like Peter Pan. Thx.

    1. margaret says:

      Hi, Alan. I have no idea, and even tried doing a little homework but hmmm….I’d be tempted to ask a place with a long experience of growing them like San Marcos Growers — I see they no longer offer ‘Peter Pan’ and maybe it flopped for them, too! : ) Anyhow, I just don’t know.

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