brrrr! overwintering tips for tender plants

brugmansiaA THREAT OF FROST LAST WEEKEND sent me scurrying to haul in the houseplants, and though it was a false alarm, it’s time: time to make plans for them and for other tender things like cannas and bananas, cordyline and a favorite pelargonium or two in hopes that what I call these “investment plants” (not perennial on their own, but carried over year to year with extra effort by me) are still around come spring. With frost warnings posted here again tonight, what better day to offer tips for how to overwinter some favorites?

First, my general thinking: No two gardeners’ potential places to stash such treasures will match in temperature or humidity, so when I say the basement works well here, your cellar might not. I have identified my best spots by experimenting, and by killing many things in the process. But every year I score another victory or two because I don’t let failure stop me. (Isn’t all gardening like that?)

And this: If I don’t have the right spot for a plant–often a combination of high light but cool, 50ish-degree conditions–I prefer to try forcing dormancy or semi-dormancy to forcing it to limp along. If you have non-hardy plants you’ve tried keeping as “houseplants” in your heated home with you, only to see them go wretched and leggy, think about letting them rest, or close to it, next time–water very sparingly and keep them as cool as you can.

What I’m doing next: adding a growlight or fluorescent hood for 14 or 16 hours a day in my cool basement to make a so-so-storage space a really good one for many more things. Again: experiment.

HOUSEPLANTS

marmaduke-begonia

FANCY-LEAF BEGONIAS: After a summer in the high shade of trees near the house, in they came (including ‘Marmaduke,’ above, and yes, that’s my childhood teddy, Iggy; and yes, I ate his nose before I was vegetarian). But first, as with all my “houseplants,” they get a physical: a checkup in the wheelbarrow or on a tarp, one at a time, that includes a trim of any battered leaves, a gentle removal of endless spiders and the occasional tree frog trying to hitch a ride, and a wipe-down or rinsing off of the pots. Best to get all the houseplants in before the heat is on indoors to make the transition less abrupt. These guys are tough, but most of them resent drafty, cold spots; I try to find enough bright but protected places.

BROMELIADS: Bromeliads (including the Vriesea, below) are great in the shady garden all summer, and great in the house all winter. I have had some of mine close to 10 years, have only occasionally repotted and simply keep their cups filled with water all year. Talk about an investment plant.

CLIVIA: This Zone 9 South African relative of Amaryllis asks what many plants from that area do: Let it go dry and cooler in late fall to trigger the late-winter bloom cycle. I simply stop watering the yellow Clivia and also the orange ones for two and a half months, and deliberately grow them in the mudroom, where the temperature shifts noticeably with the season; 50-60 is perfect.

houseplant in wheelbarrow
WITH ALL HOUSEPLANTS: Give them a physical (as my Vriesea is having, above, or as explained in the begonia paragraph); even then, you’ll import some bugs, but no big deal. Take care not to overwater (certain death) and do not feed in lower-light months, except with orchids that are out of bloom, which I feed alternating weeks. Don’t put anyone near heaters or too close to what will be ice-cold or drafty window glass in cold zones. Pebble-filled waterproof trays can add humidity to an area, as can clustering many plants or running a humidifier.

BULBS AND BULB-LIKE PLANTS

AGAPANTHUS: Traditional evergreen varieties (usually hardy to about Zone 7b) want that tricky combination of conditions that a cool greenhouse provides better than a heated home: bright light, and mid-40s or so, or as close as you can get. Perhaps an enclosed porch, mudroom, or windowed basement (or bright garage if yours stays in the mid-40s or a big warmer) can provide this. They also want just enough moisture to keep them from desiccating, but not ever to be wet. Go easy. Those that are non-evergreen, with less-thick leaves, will go dormant; place pots in the basement or another cool spot; no water required.

AMARYLLIS: I’m already withholding water the last few weeks as I will for eight weeks or thereabouts, leaving the pots in a closet in the dark, after which I’ll take them out in mid-October or so, top up the soil if needed, and water once, then place the plant in a bright spot until it wants to grow. No trying to coax a sleepy amaryllis with repeat waterings, which can rot the bulb. Wait a few weeks or a month before trying again, and once a shoot of some kind appears, begin to water regularly.

begonia-bonfire-2009
BEGONIA ‘BONFIRE’: The B. boliviensis selection ‘Bonfire,’ above, like its cousin ‘Bellfire,’ is a tuber, and wants to dry off and rest and unless you have ideal conditions (like the nearby greenhouse I have seen them prosper in all winter). For most of us, it’s just easier to let it sleep. I put mine in my 45- to 50-degree basement in the dark, pot and all, remove the withering foliage, and just let it sit, no water. Watch in late winter or earliest spring for hints of awakening: tiny sprouts at ground-level. Bring it into the light then and water carefully until fully awake. Rot from overwatering (sometimes made worse by too-deep planting) is the easiest way to kill one of these in any season, but especially when just emerging and when it wants to take a nap.

CANNA: In Zone 6 or colder, cut back frosted foliage to about 6 or 8 inches (or do this in late fall if no frost happens), then dig the rhizomes. Shake off the excess soil or rinse if you prefer. Divide into clumps of three to five eyes if really large, and place in the basement (or somewhere 45 to 55 degrees) in plastic bags left slightly open or perforated for air. Adding peat to the bags may help, but frankly I always dig up so many that losing a few is no cause for worry. And then I wake them up like this.

DAHLIA: Wait two weeks after a hard frost before cutting stems to 6 inches above the ground and harvesting tubers carefully. Note: The wait is essential for these succulent tubers to be ready to store; if there is no killing frost, I dig in November anyhow. Wash clumps, then dry in an airy, protected spot for a day or two. Store tubers layered in boxes or crates (but not in plastic) in sand, peat or vermiculite at 40-50 degrees, checking for any signs of decay once or twice during storage. Though dividing can be done before storage or in spring, big clumps may be hard to store, so at least cut them in half and wait another day for cuts to heal before stashing. Swan Island Dahlias has expert photos of how to divide.

water-pot
ELEPHANT EARS is the name people give to both Colocasia (known as taro; the “elephant-ears” with typically matte leaves) or Alocasia (generally, these “elephant ears” have leaves that are shiny). Confusing, as storing them can sometimes be, since varieties on the market vary in hardiness from tough 7B-hardy types to true tropicals, meaning they have very different tolerances. It’s also particularly tricky if you live in a cold zone where the tubers often don’t get enough summer heat to really size up. Some new varieties don’t produce big tubers at all. Small tubers don’t have enough reserves to survive, dug, all winter long, so are best potted up (or left potted up) and stashed in a cool basement. Larger tubers of some kinds can be dug, the leaves cut back to the bulb, and allowed to dry until dry to the touch before placing them in the 45-50-degree spot; some people put them in peat or vermiculite containers first. Experimentation required, and I mean experiment: I even tried setting the nursery pots of some that I like to use in water gardens (above) in a big plastic tub of shallow water in the cellar last winter. They looked like hell, but grew back into good plants anyhow this summer. UPDATE 2011: I posted an article on storing Colocasia. This year I will try overwintering some indoors in 60+ degrees and bright light, as “houseplants” and some in the cellar semi-dormant for comparison.

GLADIOLUS: After the foliage dies, harvest the corms and store dry in mesh bags with good air circulation at about 40 degrees, such as hanging in a basement. Check a couple of times over the winter for any signs of decay.

OTHER TROPICALS

BANANAS: Container-grown bananas can be cut back to about 6 inches just after light frost and stored, pretty dry, in a spot that’s about 45-50 degrees, such as a basement.  I always check things I’m keeping dry to make sure they don’t desiccate in storage; sometimes by February, I need to give a little occasional water. Bananas that were grown in the ground must be dug up before frost, which disturbs the root system, so do not cut back the topgrowth too. Instead, wrap the dug rootball in a plastic bag and bring the whole plant into the same kind of cool, dark spot as above, allowing it to dry off at its own pace, cutting it back before watering and growth begin in spring.

BRUGMANSIA: In areas where Brugmansia (top photo) isn’t hardy, the best tactic is to let the Angel’s Trumpet go dry and dormant in a 45ish-degree spot, like the cellar. It can get to be quite a giant in the ground or even in very large pots, though, and big plants are hard to store (or even get into the house or basement!), so eventually you face the reality of having to cut it back partway to even get it into storage. Mine’s going in the cellar lying down, I think; Mary, a Zone 6 reader shared in comments recently that she stores hers right in her house this way; cut in half, and resting, in an out-of-the-way corner, leafless like mine in the cooler basement will be.

HIBISCUS: Many people in cold zones know to bring these tree-like plants indoors in winter, but then try to keep them growing. A more effective tactic if you have a cool spot, would be to encourage them to drop their leaves by letting the plant go dry (like the Brugmansia, above, then store the dormant plant in a 40- to 45-degree location. Check every other week to see if a little water is needed to prevent desiccation.

pelargonium 'vancouver centennial'

pelargonium ‘vancouver centennial’

PELARGONIUMS (fancy-leaf like ‘Vancouver Centennial,’ above, and scented geraniums, or even zonals): If you didn’t take cuttings to root in August, the best way to have the freshest plants for next year, you can use this tactic from the Royal Horticultural Society (very much like the way my grandmother kept hers in her cellar, all cut back to stumps and barely alive, though she hung hers from the clothesline in paper bags). Pelargoniums with any hint of weakness or disease should be destroyed.

CORDYLINE and PHORMIUMS: These are really pricey plants, and get so much better when big, so I’ve been trying storage tactics for years with mixed results. Bright and cool is the key here (like high 40s but lots of light; little or no water), hence my adding a growlight to one area of the basement this winter to accommodate my ever-larger plants better than the two tiny windows can now. Keep a careful eye out for pests, particularly in late winter, and be prepared to trim off dried leaves come spring, when they can go out early.

JUST-TENDER WOODY PLANTS

japanese-maples-out-of-the-storage-barn.jpg
JAPANESE MAPLES or HYDRANGEAS or other small trees and shrubs that are just slightly more tender than your zone allows can be grown as pot subjects, the way I do my Japanese maples (two big pots above, seen just out of the barn in late April). I have three Japanese maples here that are technically hardy, but hate the ice and wind, so I wheel them pots and all into the unheated garage on a hand cart for the winter, once the frost takes their leaves and they are sleeping. They stay there until sometime from mid-April to early May, and require water once or twice in late winter so they don’t dry out once the potting soil thaws. Every third year they must be potted up or root-pruned. I have two friends with amazing old hydrangea collections grown just this way year after year.

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71 comments
September 25, 2009

comments

  1. Jane says

    I drag my almost 20 year old bay plant in ..and pray to it that it won’t need a pot (as stated above,. I could not do it with a larger pot) ) I lost my 20 year rosemary last year..still haven’t figured out why or replaced it). I trim it back every spring to keep it manageable and it reward some with new growth.

    I stuck a small non-prickly kind of cactus-succulent I guess- I don’t know what it is I got a piece originally from my mother-and it spread and covered most of the bottom of the rather large pot. This year it rewarded me with long stems and odd looking flowers..very nice. In another corner I stuck a varigated spider plant baby, because the mother plant was dying.. and now it is better then the original one was…loves being outside every summer. An added bonus is now one of my cats can not try to use the pot for a potty!!…stones didn’t work…!

    My Japanese maples in pots…I know it must be pot bound and keep telling to stop growing for now. I DO want to put it in the ground eventually but keep thinking we might move (I would LOVE my mini farm dream to be a reality) so I keep it in a pot so I can take it with me. What I do for it is, dig a trench in a section of the veg garden that will be planted later the following year (if at all) (I also do this for daylillies and large sedum in pots) that is as deep as the pot is tall. Put the pots in the trench and when they lose their leaves, I fill in dirt to the depth of the pot. After it freezes, I lightly mulch with hay (only because if they were in the ground I would and also again..in case we move in the winter, I want to be able to dig them up…
    It fools the plant into thinking it is in the ground…I also have done this with other potted plants, such as phlox in pots, and hosta, rhubarb (from my grandfathers plants) and hydrangea….(all because we “might” move and I HAVE to take some of the plants with me…)

    So far everything comes back up in the spring and as long as we are still here..they decorate my covered porch in the summer with some east morning sun for some and south sun with some shade for others that need sun…I also have a bridal wreath shrub, I trim back to keep it small-ish for now, that I got from a neighbor, in a pot, and do the same with it.

    My garden is made up of many plants from family and neighbors how could I part with them if I moved..they are as important as my babies…
    Jane, LI zone 7

  2. chigal says

    Hi — any tips for eliminating aphids before bringing plants indoors? I’m reluctant to spray because of the cat, but washing them off with water seems to be a temporary measure. I’m afraid I’ll be battling aphids all winter.

    • says

      @Chigal: I would give everything a VERY good spray with hose-end sprayer beforehand and also you could try horticultural soap/oil, but really the idea of to dislodge them and then get the plant inside. I sometimes shower things indoors once or more, too.

      Welcome, Jane. Here (Zone 5) I cannot plunge any pots except plastic ones, which I do a lot; clay would get destroyed by freezing and thawing of the ground, so I line a lot of my pots with plastic nursery ones and then plunge the plants in those and wheel the clay into the shed. Sounds like you have quite the collection of goodies! Hope you see you again soon.

  3. Deirdre says

    We don’t usually get frost until November here, but there are quite a few things that don’t like rainy Seattle falls. So, today I preformed the melancholy duties. The orchids have been brought in, and various houseplants sit at their windowsills. Plants that don’t mind cool, but do mind wet have been put into sheltered positions on the porch or under eaves. The deck chairs, umbrella, porch cushions, and porch rug have also been brought in. Sigh.

  4. Deirdre says

    My sister gave me an amaryllis in a pot for Christmas a number of years ago. There was an asparagus fern and an Algerian ivy in the same pot, so I can’t just stop watering it. I water it year round. It never goes dormant, and it blooms twice a year; two stalks at a time.

  5. Lynn says

    Thanks for the tips about the clivia, I finally got mine to bloom last year due to the information I read about putting them to sleep. It seems like a brutal long time that you suggest. It’s worth the bloom!

    • says

      Welcome, Lynn, and no problem; happy to help. It really is what so many South African plants need: cooler and dry, to get them in the mood to flower. See you soon again.

  6. Fred from Loudonville, NY says

    Elephant ears… About eight years ago, I bought two elephant ear tubers from Wall Mart. The two tubers have now turned into a bushel basket of elephant ears. In Mid October, I will dig the tubers up, cut off all the leaves, and MOST of the stems, squirt them down with the hose, and let them dry on the lawn for a day. After that I will just put them in a bushel basket, for the winter, in my semi-heated garage, and forget them. In the spring I will wrip off (un-peel) the dried remaining skin, discard the part of the tubor that is then CLAY LIKE, and dead, and get ready to replant anything that looks firm and healthy. Even thought I have started , YEARS AGO with coconut sized tubors, the tubors now are much smaller. EVEN the smallest tubor is still capable of producing a big plant. When i first planted the Elephane Ear plant, I did not know that they were late at emerging. When they showed NO sign of growth, I even pulled back the dirt, to see if they were still there. I also DON’T recommend planting them in plastic pots. The first year I planted them, I put them in nice plastic containers. The root systems were so strong, that they broke both of the containers. Now they are ONLY planted in the ground. Dahlias…Putting the dahlias in sand, peat , or vermiculite is too much effort. My grandmother grew them for years, and she dug them , washed them, and JUST stored them in card board boxes with a news paper on top of the box, under the stairs in her house. Think about it, the dahlias that are sold in the market are just in plastic bags with a SMALL bit of peat, that I wonder is more for show, than practicality???. AND as for amaryllis, when you buy them in the store, they are piled in crates, one on top of the other. No product is around them.

  7. Maureen says

    I have had great results by placing my rosemary, bay trees and other some what tender plants, in the garage first then when it gets really cold, they go into the back of my station wagon. As I drive around I try to park with my back facing the sun. Its remarkable how well it works
    Maureen

  8. Maureen says

    I live in zone 6, and I do get get strange looks as I drive around in January & February. It works for me.
    Maureen

  9. chigal says

    Thanks for all the wonderful tips! I’ve been wondering if I’m doing right by my woody herbs (and oregano), or just wearing them out. I bring the pots in when it’s cool but still warm enough for open windows, to get them acclimated. Then when it’s really cold at night, I close up the window (which is sunny, cold and drafty) and cut way back on water all winter. I might lose a chunk here or there, and I have to be very selective about using them while they’re not growing. But so far so good.

  10. Bobster says

    The dance is done….for the next six months or so anyway. Just finished bringing in the last of the houseplants from their summer vacation. The better half is threatening to hide my copy of Ken’s ‘Making More Plants’ until after the late winter manic gardening urge has passed. MUST give away more plants next year!

  11. Harley says

    Any tips for dancing with Alstroemeria? I have three large clay pots with compact “Princess” varieties I would like to keep going. I live in zone 5b (Richmond, Mass).

    • says

      Welcome, Harley. I have tried to find something definitive, as I have never tried it. Anecdotes seem to range from “mulch it” (in Zone 6) to “dig it” to “grow it in pots.” The most authoritative reference I have found is Missouri Botanical Garden, with an explanation on this page. Sounds like digging is a bit of a drag but what you will need to do. Hope this helps.

  12. Harley says

    Thanks for the link Margaret! On that page, clicking on General Culture: gives me the recommendation:

    “Bring potted plants indoors before first frost.Store in cool shady place and keep soil dry. ”

    I’ve got a cool, shady, basement bedroom that may work. In they come this weekend.

  13. Rae says

    I have been able to cross off about 22 items on my list, but that includes putting away my fairies and their accoutrements away. Maybe I should move farther south but I do like to keep alive tender plants. Some of those I have brought in every year into the house, agapanthus, gardenia, stephanotis, and hibiscus. My condo has windows with radiators underneath. A little tricky. My crepe myrtle in a pot goes into a window in an unheated garage. Now my newest experiment, a plant stand on an enclosed porch that gets sun in the mornings. I have brought in some pots of herbs, my specialty (annual) fushias and two mandevilla vines which were beautiful all summer and fall. Those I cut back somewhat. Then I put a transparent shower curtain around all of these plants with a fabric cover over the top. We’ll see what happens.

  14. Brigitta says

    Hello Margaret,

    I have been hoping to find an incredibly informative website on gardening like yours for YEARS. Thank you for the wonderful pictures, posts and the generous gardening information . BTW, your book speaks to me on so many different levels, and so I am going to grab it once it hits my book store.

    Thank you!

    Best regards,
    Brigitta

    • says

      Welcome, Brigitta. You are so sweet to say all this, thank you — so glad we found each other! :) I do hope that you will enjoy the book as well. See you soon!

  15. Linda Pastorino says

    Hi Margaret,
    I have less understanding about house plants and tender perennials so I’m confused about over wintering. Is it necissary to store above mentioned plants ( may of the ones on your list) in a colder basement or in none lit situations or is this only because there might be lack of storage and window light in most homes?
    Reason being is that I took out the house plants into the garden, some of which are old some of which I purchased new and have never yet been in the house. Why would I not be able to take them in a sunroom or conservatory instead? I will bring in all this week and would appreciate any help with this. I have two conservatories on the house with sky lights, one with radian heat and watering facilities.
    thanks
    Linda

    • says

      If they are typical foliage houseplants — fancy-leaf begonias, philodendron or other tropical leafy creatures, etc. — yes, grow them inside as houseplants in winter if you have room and light. The ones that I try to store semi-dormant are the ones that I cannot provide a satisfactory combination of light and temp for (things that might be hardy in a garden in the Southeast, for instance, but not here). Another exception: things with tubers or bulbs, that want to go dormant and rest awhile (like my Begonia ‘Bonfire’ in the story, or things int he ground like cannas and so on). But for less fussy things, things we often think of as “houseplants,” yes, if you have bright spaces indoors, lucky you.

  16. Kevin says

    Hi Margaret. a great book for all intersested in over-wintering tender plants out of their normal growing zones is called Hot Plants For Cool Climates by Dennis Shrader and Susan Roth. Lots of great tips and photos plus a great appendix with loads of advice on many different plant species;highly recommended for the tropical ,tender annual plant lover!

  17. Kevin says

    HI Linda, Most of us would LOVE your situation! With great light and some warmth, most tender plants will do very well with your indoor arrangement; watch out for pests though whitch thrive in an indoor dry winter enviroment Keep the foliage clean and mist with water to raise the humidity when the heat gets turned on Avoid over watering and skip the fertilizer until new growth in the start of the new growth cycle. Don’t be afraid to cut back large or over-grown plants to accomadate their indoor growing enviroment They’lll bounce back fine when they’re moved back outside after all danger of frost has past and they have been accclimated to the stronger sunlight again

  18. Cecile says

    Thanks for the tips Margaret ~
    A former Californian from Santa Clara Valley, (originally known as “Valley of Hearts Delight”) where I could leave things in the ground all year long and have a pretty decent looking yard in the Winter. Now I am happily learning to adjust to 3 acres and cold rainy winters with chickens and doves in the Pacific NW. Desperately trying to save my favorite plants from perishing in the Winter. I wondered if the ones I lost in the barn last year were not watered enough ? The houseplants that survived had to be under a light or they would not have made it. No central heating so it gets dang cold up here, although not as much snow as you get thank goodness. I have just one chapter of your book “and I shall have an abundance of peace there” to go and I wish is wasn’t coming to an end. It has been a nice friend to look forward to. Also enjoying your blogs. Thanks for sharing.

    • says

      Thank you, Cecile, and welcome. How nice of you to tell me how you are going with the book.

      I know from my friends in the PNW that the last winter in particular was total madness — and a couple have been really difficult in recent years. They lost a lot of things, too, so don’t beat yourself up!

      Chickens and doves sounds like a lot of fun.

  19. says

    Heyyy, Margaret,

    As a Darwinian gardener, I much appreciate your post; your advice will help me extend limits I love to push – and keep a few more of my experimental subjects alive.

  20. Dahlink says

    We have several taro that spend most of the year in our pond. We bring them into our conservatory in large rubber trugs to spend the winter. They typically look ratty around March and April, but shortly after they go back into the pond they perk up amazingly. Something large got into the pond this summer (we suspect a great blue heron, which got away with several green frogs) and knocked a big pot of taro into the water and shredded the plant. In order to save it we had to divide it and now we have three where we had one before. Fortunately I bought more trugs recently!

  21. Leo in NJ says

    I want to avoid last year’s problems with my potted Meyer lemons.

    Lat year I procrastinated, left them out until actual frost threatened. Brought them inside and they dropped thier leaves. Thought I was going to lose them, but theyurvived.

    I fugure the shock to low light (even a South window & grow light isn’t sunshine), dry air (will humidify this year) was too much for them. \Will be bringing them if not inside at least to the shady porch beginning now to give them time to “harden”.

  22. Cheri says

    On the subject of the elephant ears… I had gotten one last year on a whim at the local garden center. I had read I believe on your site that they were good for ponds. We had recently dug one and nothing was growing in it yet except some cattails that I had saved from the marsh.
    I over wintered it like a house plant and it looked so bad by spring yellowish and wilted filled with spidermites. When I put it out this spring it lept and bounded in its pot and is huge now. Well now I have the bug. I had to get the black ones and the spotted ones. I have brought them all in this weekend because in the NE ohio area they are calling for 30’s for night time temps. Thanks so much for the gardening information and inspiration. It is hard to find good sites on the internet anymore.

  23. Katy L says

    What about succulents and sedums? I have planters with the most gorgeous varieties of these types of plants. How,would winter them over? Kept with other house plants they get pathetically leggy and pale in no time at all….yet I hate to let them be taken down by the killing frost (that is threatening to get us any night here).

    • says

      Well, Katy, it depends how hardy they are — what species/varieties — and how frost-proof and large the pots are, too. I have sedums (like ‘Angelina” and others) under my Japanese maples, and I drag the dormant trees into the garage (unheated) around Thanksgiving. The trees and the sedum overwinter fine in there, sleeping. No special light (hardly any, actually) and no water till like February or March, and it has been years.

      Are these hardy in your zone of in the ground or ????

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