clivia, staking, viburnum leaf beetle, chestnuts & more: q&a with ken druse

YES, IT’S US AGAIN, me and Ken Druse, here to answer your latest crop of Urgent Garden Questions about topics as diverse as using landscape fabric (or not!); viburnum leaf beetle; blooming and then overwintering Clivia; artistic staking of dahlias and other plants; American chestnuts, and more.

Ken is a longtime garden author and photographer, with many books to his credit including “The New Shade Garden” and “Natural Companions” and “Making More Plants.” He can be found at KenDruse dot com.

Read along as you listen to the Oct. 29, 2018 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).

the october q&a with ken druse



Q. Uh-oh. I can hear in your voice that you’re working on fall cleanup over there. [Laughter.] Oh boy. So let’s get right to it, but I guess I looked in some bulb catalogs—I’m browsing through them the other day and I’m thinking to myself, “It’s already well into October and I haven’t ordered any bulbs.” Are you planting any?

A. I was looking at a catalog and I thought, “Good thing it’s August,” only it’s not August.

Q. [Laughter.] I know.

A. And I didn’t order any. I can’t believe it.

Q. I know. I know. I think I might put in a last-minute order for some minor, little guy things, but that’s about it. I don’t think I can undertake… It’s been so wet and so crazy lately. You know, I’m afraid to, this last minute, tackle anything.

A. Well, some things might be sold out. That’s kind of a problem. That happens when you order too late, but you know, they say you’re supposed to get the narcissus in the ground by September. I pretty much never do.

Q.  November?

A. [Laughter.] Well, I figure if you can get a pick ax in the ground-

Q. There you go.

A. And make a hole, and plant the … Well, I’m exaggerating, but you can get away with near murder and plant them anyway. Especially if you have bulbs you already bought and you haven’t planted, just get them in the ground.

Q. Yes because they’re not going to last in the garage, that’s for darn sure. You know?

A. Yes, yes.

blooming and overwintering clivia

Q. So we do have lots and lots of reader and listener questions. One is about clivia, which is not a bulb, but actually kind of looks like an amaryllis if you look at the plant growing, the leaves, the strappy leaves.

A. Right. But it’s evergreen.

Q. Yes. Adrienne, who’s in Northeast Pennsylvania, Zone 5, “an expert gardener except when it comes to houseplants,” Adrienne says. A friend gave Adrienne an old clivia last fall, and said, “Put it in a window, leave it alone,” and she watered it minimally last winter, she says, kept it in indirect light in her living space. It never bloomed. She put it outside on the deck, out of direct baking sun, but watered it minimally; didn’t repot it. Uh-oh, uh-oh, what’s going on? Gave it some fish emulsion a couple of times, but wondering how to make this plant happy and bloom.

Do you have any clivia?

A. I do.

Q. Me too, yes. Are they oldies, big oldies?

A. One of them is really old with lots of leaves and I haven’t repotted it. It’s been in the pot for years. I feed it a little bit in the spring, but I don’t feed it that much, and I don’t put it in any sun outside. It’s in very bright light. It blooms its head off. It doesn’t bloom in the winter. I know that yours bloom in the winter, but mine blooms-

Q. No, no!

A. Well, I usually get a bloom in late winter and then more. It was blooming, I think, in – I was going to say August, but what month is this?

Q. This is yes, October.

A. I think it did have a bloom in July, believe it or not.

Q. Yes. Well, and that’s the interesting thing about them. You said mine bloom in the late winter, and that’s really only if I concentrate and give it exactly what it wants, as if I’m like a clivia hobbyist and I’m going to bring my plant to the show and I’ve got to have it blooming on time. There’s a formula for doing that, working back from showtime, and most of the clivia shows are late March, like the 20th of March, something like that. You can kind of count back.

But the key is dry and cool.

A. Right.

Q. And they say, a lot of the experts say October 1st to January 22nd—not to be too precise. No water and during that time–I mean, that’s drastic, right? [More on growing clivia from Longwood Gardens.]

A. Yes.

Q. Between 35 and 55 degrees for that period of time for a minimum of five weeks. So it has to be at least five weeks, no water between October and January but at least five weeks of that chill as well. That’s a hard combination to come up with in your house, you know what I mean? Even a mudroom or you have a sun porch, right?

A. Yes, but how are we going to get it down below 55 degrees if it’s not?

Q. Right, exactly.

A. We’re not going to participate in the show, I think.

Q. I think we’re not going to make the show. But again, they have a timeline, and you hold the plant dormant they say until eight weeks before the showtime, and then you start bringing them out of dormancy by watering gradually and raising the temperature to 60ish so that they’re not rushing into growth and pushing their flower stalk too fast.

But again, for the regular folks like us, you find your brightest, coolest place and stop watering.

A. Right.

Q. And give it that … It’s sitting there, it’s happy, it’s got some light, but you give it no water all winter. I think that’s where people get a little confused. And definitely don’t feed it in the offseason.

A. Right, right. So dry and as cool as you can possibly get it in the house. We don’t want it to freeze, but-

Q. No.

A. Definitely cool and dry and that’s how you get it to bloom. And if you have a very young plant, it’s not going to bloom.

Q. No, that’s the other thing.

A. They have to be kind of mature.

Q. That’s the other thing. And I think changing its regimen—and I’ve noticed this with other things that I’ve adopted from somewhere or someone, when this was an adopted plant, a gift plant or whatever. Sometimes the first year in a new regimen, plants also sulk or are off-schedule, if that makes any sense.

But if you don’t have enough cool in the late fall into that early winter, if you don’t have enough cool—like my mudroom might be 55 or 60ish, it’s not 45 or 50, it’s just not. So my plants tend to bloom more like you said, July or August even. A lot of times June would be what you’ll get. It kind of depends on your conditions. Anyway, that’s for Adrienne. Hopefully that will be helpful.

using landscape fabric (or not)

Q. A totally different subject, Joshua is asking us about, he’s in the South Jersey area.

Tough year in Zone 7A he says; lots of rain, lots of heat then, etc., critters galore. He decided that he was going to kind of get a clean slate during fall cleanup, and this is in the vegetable garden.

He says, “I was going to put a couple of inches of leaf compost over the veggie garden to go into next spring with a replenished spirit and garden soil, and should I place the landscape fabric over the top of that and pin it down, stake it down, or would it be better not to?”

So landscape fabric, where are you with that?

A. Oh my gosh!

Q. I know.

A. There’s so many things that people try to put over on us gardeners. It’s really a shame. I can’t think of any use for landscape fabric, really.

Q. That’s funny. I hate it as well. Having once used it many, many years ago in creating a path, and putting it underneath the mulch material of the path, and lo, these 25 years later or something, it’s still down there. It occasionally pops up at the edges. It’ll never deteriorate.

A. I’m not even exactly sure what it’s for.

Q. Well, I think it was one of those things where people were laying patios and they imagined they didn’t want any weeds to ever pop up through the cracks or walkways, or again, like a mulched path, it was supposed thwart them—it’s an underlayment to thwart weed stuff coming up into the path or the cracks or the crevices.

A. Yes, but don’t you think most weeds come down from the top?

Q. Well, I do, a lot of them, but there are also things that go sideways and up and whatever.

A. Yes, that’s true.

Q. So I think that might have been the idea, but yes, I’m not crazy about it. How would you, in  a vegetable garden—want to get a fresh start and didn’t have a great season—what’s the condition you would leave it in this fall?

A. Well, I’m not sure what exactly the point of this is, the idea. Is it to keep the material on the top from blowing away-

Q. Yes, I think maybe, yes.

A. Or is it to keep some things from getting down in there?

Q. I think maybe to keep it in place, but I don’t worry so much about that. I put on my fall amendments heavy enough that, once they get wet from the weather, they kind of stay in place.

A. Right, he didn’t say it was leaves. He said it was-

Q. Leaf compost.

A. Compost, right.

Q. Yes.

A. I don’t think there’s going to be a problem. Just skip the cloth.

Q. Yes, I think skip the cloth too. Good, O.K.. So we’re in agreement. We’re finally in agreement! [Laughter.] No, I’m only teasing. I’m teasing!

by Andrew Newhouse for acf.orgamerican chestnuts?

Q. I had a funny question about chestnuts, American chestnuts, which were destroyed by a blight, as we know, a long time ago, as we’ve all heard. This reader/listener—she said she and her husband have a farm in Western Pennsylvania in the mountains of the so-called Chestnut Ridge. They have discovered on their land a 50-foot tall, 8-inch caliper, what they think is an American chestnut.

There were 20 seed husks on the ground, three seeds in each one, so about 60 seeds. She wants to know could they be propagated or whatever?

I know this is probably not something either one of us has done since chestnuts are not extinct, but mostly extinct. So she wanted to know, Heidi wanted to know, some of our suggestions.

I right away said to Heidi “American Chestnut Foundation” because I think they have a great website. Have you ever seen it? Have you gone to that website? [Above, open American chestnut bur from ACF website, by Andrew Newhouse.]

A. Yes, a long time ago, but yes, I have.

Q. Yes. They have great resources about, first of all on ID because there are chinquapins, and others, then there’s Chinese chestnuts and so forth, other chestnut lookalikes that aren’t American chestnut. They have information, and you can even send in [twigs with mature leaves] and get them identified, tested.

A. That’s a great idea.

Q. Yes, they’re great. They have harvesting tips—like once you pick them up off the ground, do you try to pry them open and take the nuts out or not? (I think the answer is not.) What do you do in winter, and if you were going to plant them, the no-no about, as you would probably guess, guess what not to do? Plant them out in the garden because …

A. Someone will eat them.

Q. I wonder who that would be! [Laughter.]

A. I mean …

Q. The same critters who would love to dig up all the bulbs that I didn’t plant, right?

A. Yes, right.

Q. Yes.

A. I’ve actually started the Chinese chestnuts from seed. They’re very easy to germinate, which is irrelevant. But I kept them moist in the refrigerator and they sprout in the refrigerator. And then potted them up, but what am I going to do with a Chinese chestnut tree?

Q. Right, right. The other thing is that, and I saw this on the American Chestnut Foundation website, is this disclaimer that if there’s only one tree, it would not have been pollinated, so the resulting nuts would not be viable.

A. Oh, so you would have nuts but they may not be-

Q. So yes, it is possible.

A. That’s interesting.

Q. Yes, yes. They wouldn’t be fertile or whatever, yes. Anyway, I think it’s just ACF.org for people who are interested. That was a different kind of question, not one we had gotten before.

A. And they have information on the “disease-resistant” varieties that people are working on, which is wonderful.

Q. Yes. Yes, so a worthwhile place to have a peek and learn more about chestnuts, their history, their future, and their relatives, too.

creative, artful staking

Q. Carolyn wrote to us, Ken, this is one that you’re going to have to answer because I’m not so good at the-  [Laughter.]

A. I love it when you set me up like this.

Q. Well, you’re more artistic than I am.

A. Oh, wow.

Q. I mean that honestly. You’re a painter, you’re a photographer, you’re crafty and you have those kinds of … You have some skills that I’m not as good at. So hopefully you have this skill, which has to do with staking things.

Carolyn had read a recent interview I did with the person who did the dahlias at Longwood Gardens and said the stakes [below] really bother her.

“They’re ugly,” she says, “and difficult to hide if one plants the dahlias in the garden,” and not in just a separate cutting area where you can use more workmanlike supports. She says, “I know one should have plants in front of them to hide some of the stakes, but if the dahlias grow large, they topple over. They’re top heavy. What’s good staking?”

And this really applies to any plant, staking tactics. Do you do a lot of staking in your garden?

A. You have to. I have to. [Laughter.]

Q. So some examples?

A. Well, it’s funny because I’m listening to you and I’m thinking dahlias are not really very pretty plants.

Q. No.

A. You don’t grow them for the nice foliage. Some of them are very tall, 5  or 6 feet tall, and then they have those very heavy, giant flowers. The staking is more utility. It’s something to do. But with dahlias, when I plant the tuber, I put a stake in the ground at the same time and I know where my tuber is. I use probably a bamboo stake, that’s what I use most often, and I’m thinking about utility, I’m not thinking about beauty.

But if I were to think about how could I do something for dahlias that was a little more attractive, I might make an open fence or something out of stakes on the north side of the plants so that I could tie them to it later, or a teepee, something like that.

Q. A teepee would be nice, like by that you mean like a tripod, taking three bamboo canes, sinking them in well, but then gathering them at the top with some cord or whatever, some twine?

A. Mm-hmm.

Q. Yes.

A. I think if you want it to look good, just make it intentional.

Q. Right, so that it doesn’t look like, “Oh, your stake is showing,” it looks like, “Oh, right.”

A. And it’s bent and it’s crooked. Make it straight.

Q. Right, important.

And one of the other things you can do, if you don’t want to have an intentional device like you just said, like the fence behind them, not a literal fence, or a teepee or whatever, would be—and I don’t mean this snidely–but to grow some of the less tall varieties. Because there’s such a range of flower colors and sizes and shapes in many sized plants. Also, to pinch a little, not a ton, and also obviously to grow them in full sun so that they don’t stretch.

In other words, anything you can do to minimize them getting to be sky-high, which is going to be the biggest problem at all, having to have a too-tall stake or a very tall stake and have them flop over anyway at the end.

But I like the idea of making it intentional. I think that’s good advice for supports in general, right?

A. As you’re saying this, I’m thinking you could make girdles or corsets out of chicken wire, which would be intentional but not necessarily pretty.

Q. Right. No, no, no. But you’re saying intentional like, “This is part of the look of this garden”-

A. Yes, I do mean that.

Q. Instead of aesthetically intentional. Yes, yes.

A. Mm-hmm (affirmative).

Q. Yes, yes. No, I agree. I think the other good thing about the bamboo is that, if need be, say you put it in extra tall and the plant doesn’t grow to that height, you could typically take your shears [or the lopper] and snip off some. You don’t have to have it sticking out. But you’re going to have it sticking out while the plant grows up no matter what, so your intentional idea, like the fence backdrop or anything, is probably better.

A. You know, it’s funny. The bamboo stakes are that odd color of green. I don’t know how that started or what that’s about.

Q. Ugh, I like the natural ones!

A. But I have painted my stakes in my lifetime. Sometimes I’ve painted them pale green to match the plant and I’ve also used our world-famous invisible color [Benjamin Moore Spanish Moss, below] and painted some stakes and you can’t even see them.

Q. Which is kind of like a dark taupey color?

A. Mm-hmm.

Q. Like a Weimaraner color, Weimaraner dog color? That kind of color?

A. Well, I always think of it as the color of bark and dirt, but Weimaraner’s nice.

Q. Yes. Weimaraner, we’re going to rename that paint, Weimaraner. Yes, I like the natural color. I can’t stand the green ones, besides the fact that stuff comes off on your fingers if it’s wet.

A. That’s right.

Q. It’s revolting. It’s not a natural green. To me, it doesn’t look natural. I like the undyed ones, but they’re harder to find.

A. They’re harder to find, right.

Q. Sometimes you have to order them. Yes. All right, staking.

viburnum leaf beetle,

plus shrubs & trees for wet clay

Q. So we have another question. Drum roll please.

A. [makes drumroll noise.]

Q. Cheryl is asking: She’s in Ohio Zone 6A. She’d like to plant a native focal-point understory tree or shrub that can handle wet conditions in clay soil that is alkaline. Oh my goodness. [Laughter.]

It’s on the edge of the woods and it’s near black walnut trees. A lot of complexity. But she did a substantial amount of homework, and she got kind of excited about a particular Viburnum, which was dentatum, Viburnum dentatum. And then we she called local nurseries to see if they stocked it, she was told by a couple of places that they stopped purchasing it because of the Viburnum leaf beetle, and how much damage it does to that particular species. [Time-lapse video from Cornell above of larvae eating leaves.]

Have you ever had VLB in your garden, Ken, in New Jersey?

A. I’m not quite sure. I have something that’s disfigured the viburnums and the leaves are all puckery. I don’t have that currently, but is that symptom of the beetle?

Q. Oh. No, but more like holes and stuff, like it’s been eaten?

A. No. You mean like a Japanese beetle look kind of thing?

Q. Yes.

A. No, I haven’t had that.

Q. I mean no, not exactly that, but yes, that direction. Skeletonized or eaten like an insect, a herbivorous insect.

A. Finally, there’s one thing I don’t have.

Q. Oh good, O.K. I have had it and it’s very interesting. Cornell University, for many years, has maintained a Viburnum leaf beetle mini-part of its website. It rates all the species, both native and Asian ornamental ones, from highly susceptible to most resistant to the beetle. You can choose, using that as a reference.

So dentatum, the arrowwood, is one of the highly susceptible ones. Those nurserymen were right in telling her that, that it was a risky business. I have the beetle and what I do is they also love the cranberry bush viburnum, both European and the American ones—they love that with little maple-like leaves.

So what I do is I have, in two areas of the garden at extreme distances—like not in the main beds or whatever but where you don’t see it—I have one big plant of each of those. The beetles go to those. I use it as a trap crop like farmers do. When they have a particular pest, they may, a few weeks earlier than their main crop that they don’t want to have get eaten, they may plant a relative of that crop at a distance and lure the pest. Ha ha, how tricky!

A. Is it like sacrificial shrubs?

Q. It is indeed. Exactly, but like a trap crop. If you don’t want to some kind of brassica pest to eat your main crop of a brassica, you, at a distance, plant radishes really early and you’ll have lots of those pests on your radishes. That’s the thinking. So I have some of the most susceptible ones so that my moderately susceptible ones don’t get as damaged or damaged.

And then the other thing is that from late fall until before the beetles wake—the larvae hatch again in spring—you see these little bumps on the newer twigs towards the ends of the branches that are egg cases. They’re overwintering their eggs on the twigs of the viburnums. So if you cut those off and throw them in the garbage, get them away, you’ll have fewer beetles. Bump-like egg cases on twigs in fall, above; photo from Cornell, by Mary Woodson.]

Have you ever heard of Spinosad?

A. Yes.

Q. Have you ever used that for anything?

A. I believe I have. I don’t remember the results. It was a long time ago, but I have, yes.

Q. Yes because I’ve read, also, that that’s one thing of the natural things that can be applied [to direct contact with the insects], but I have to look more into that.

So what are you up to? Are you in throes of cleanup? [Laughter.]

A. Well, I’m sitting here thinking of what you could plant, what that woman could plant in that situation. I can think of a lot of things but they want acid soil, unfortunately.

Q. Right.

A. I have alkaline soil and I have water. I’ve planted some Taxodium. [Above, the dwarf Taxodium ‘Peve Minaret’ in Ken’s garden. Photo by Ken.]

Q. Oh.

A. And they’re handling it, but they’re trees, although they are dwarf ones, and sycamore, and Nyssa sylvatica. There’s some interesting dwarf ones of that and some larges, just so we don’t leave her up in the air completely.

Q. All right, good. So we’ve had a few suggestions. Ken, we have squandered another segment.

A. Oh, really?

Q. Yes. But I’m glad to speak to you. Now, get out there and do your cleanup.

A. Well, I’m still schlepping plants in, if you can believe that.

Q. So am I, so am I.

prefer the podcast version of the show?

MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its ninth year in March 2018. 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 Oct. 29, 2018 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).

  1. kate swift says:

    round metal tomato cages also work great for supporting dahlias. They tend to disappear in the foliage as the season progresses. Use the larger, sturdier ones as dahlias will topple the small ones.

  2. Harriet Robinson says:

    I don’t think the question about landscape cloth was really about the cloth. I think it was about the wind blowing the leaves away. My veg raised beds get wind. I put wires/ fencing over the leaves after I spread them. Chicken wire frames are great if you want to go to the bother of putting wood around the outside. I have some from an old portable hen yard that are the exact size of my beds and I use them year after year. I trellis peas and cukes on what I think is sheep fencing. I use these in winter to hold the leaves down. A roll of fencing can be unrolled onto a garden and re-rolled in the fall. There is some expense in buying them, but they never wear out. If I don’t have quite enough, I may lay parallel grade stakes, a few bricks here and there, etc.

  3. Carrie B. says:

    I’ve see the tomato cages with some bamboo stakes added to hold the cages down to be sturdier against the wind. It works well in a garden bed situation and is hardly noticeable.

  4. Ann says:

    Thank you for covering this topic!
    We had a severe infestation of VLB on an old Viburnum dentatum this spring, for the first time. Those little VLB vampires ate every scrap of leaf off our shrub. Heartbreaking. The little larvae were everywhere. Of course it was too late to apply Horticultural oil. BUT…a day or two later, help arrived! A flock of cedar waxwings found the larvae and kept coming back over the next week or so. They cleaned it right up! And then the Bush re-leafed!

    Of course there were no berries this year since the larvae ate the flower buds too. But since I’m sure some beetle pupae are in the soil now, I’ll be ready in March/appropriate time with the HO. I’ll also look into the Spinosad.

    The berries of Arrowwood Viburnum are awesome for attracting birds. I once counted five flickers in our shrub, all gobbling the berries. Needless to say Bluebirds, robins, cedar waxwings. Mockingbirds and catbirds all love the berries too.

  5. Melodie Sept says:

    Perhaps Lindera benzoin would work for Cheryl in Ohio. I’m in southeast Michigan and my soils are alkaline as well. I have planted several Lindera in my woodland garden, near my black walnut. So far I haven’t had any issues with chlorosis. The ones that are performing best are growing in a naturally low spot where they soil is a bit clayey and moist. The ones planted under white pines need to be irrigated. I’m planning to relocate them.

  6. Gladys says:

    Naturalist have found a stand of American chestnut trees in Pennsylvania, I believe. Not sure the ACF acknowledges that, though.
    Re: the stakes for plants, Tower Hill Botanic Garden has had wonderful, colorful stakes for vegetables, etc. in purple & other bright colors – really well done! Then there is always color in the garden, even before bloom. Not sure the material they use, but you can check at http://www.thbg.org.

  7. Nancy Marr says:

    I am puzzled by your comments about green bamboo as if it is not natural. I have a stand of bamboo and the younger plants are green naturally. They turn tan when they are older and dying.

  8. Heidi Husnak says:

    I am in a completely different climate – Los Angeles. I have tended clivia for years at the local botanic garden and found them to be resiliant and “abuse tolerant”. I’ve had them at the house for over 40 years. What is amazing is that in this climate they are a colorful striking bloomer in shade! We sell them in full bloom at April plant sale. At the South Coast Botanic Garden they are underplanted in the spectcular Banyan grove – a striking statement and drought tolerant. Always interesting for someone in a vastly different zone to see a utility plant seen as special.

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