dennis schrader’s tips for overwintering tender plants

dennis schrader’s tips for overwintering tender plants

Landcraft Environments propagates to sell wholesale to nurseries, landscapers, and botanical gardens. (Follow them @landcraft_environments_ltd on Instagram.) With his husband, Bill Smith, Dennis Schrader has since 1992 operated Landcraft Environments in Mattituck, Long Island—specialists plants that add seasonal color and texture, and the look of the tropics to the garden. (Like the coleus called ‘Fishnet Stocking’ above.)

He’d like to encourage us to start a collection, too, and offered tips on how to keep them happy—tactical advice on plants we should consider investing in. Our conversation started with a “New York Times” article I wrote a couple of weeks ago on the topic, and continues here.

And we also talked about the emotional side of carrying a plant over year to year and beyond. It turns out I have a plant I got from Dennis decades ago that I have been stashing every winter since—and that he lost one year to disease. Guess what’s heading back to him from my garden soon? (Below right, Dennis with Bill Smith, in a photo from The Garden Conservancy.)

Read along as you listen to the October 2020 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on Apple Podcasts (iTunes) or Spotify or Stitcher (and browse my archive of podcasts here).

Margaret Roach: How’s it out there?

Dennis Schrader: Fall is here.

Margaret: Yes.

Dennis: It’s great, it’s cooling off, very nice.

Margaret: Yes. So before we get started, I should say I was so happy that we did that “New York Times” story together a couple of weeks ago about this subject, the mad stash, right?

Dennis: Yeah, yeah. It was fun.

Margaret: And thank you … it was very popular, and it was fun to read the comments. Lots of people jumping in and saying their successes and their failures with different plants, you know?

Dennis: Mm-hmm.

Margaret: So this is something people love to do, is to try to figure out, right, how to carry over a beloved plant, so-

Dennis: Yeah.

Margaret: You identified several sort of tactical categories, like … because not every plant will want the same thing, to survive the winter in this sort of false environment, not their native habitat. And I just wondered, can you tell us about sort of how you group them, and how you thought about that?

Dennis: Yeah. Well, first off it’s … We get these plants, these are given to us or purchased, and we nurture them all summer, and then we want to do something with them, just not have them hit by a frost and that’s it. So a lot of it has been experimenting with different types of overwintering. So some of the easiest ways are collecting from seed, and doing cuttings, or even actually just bringing the plant inside and treating it as a houseplant. There’s different ways to store them.

Margaret: Some are even stored dormant, like bringing it in as a houseplant and keep it awake, or bring it in-

Dennis: Right.

Margaret: …as a houseplant and let it nap. And that’s one of the things that I frequently, earlier on in my gardening career, I used to try to keep everybody awake, and some would rather go to sleep, right?

Dennis: [Laughter.] Right. And you also run out of room; it’s a space issue most of the time.

Margaret: Yeah.

Ensete, the red-leaf Abyssinian bananas, he would … It got so big, with this huge trunk, he would keep it under his dining-room table [laughter]. So it would do fine, except you were kicking it, you would think it was a dog or something under there, and you look and it’s this 6-foot stump. But it worked for him.

Margaret: So the banana under the dining table, is that going to be in the reference book about this? [Laughter.]

Dennis: Yeah, right.

Margaret: So what we’re really trying to do is we’re trying to sort of categorize things as we look around the fading garden right now, wherever we garden, and match them to the right tactics. So like with seed, like what would be the kind of … What are just a few examples of things to do from seed?

Dennis: Oh, zinnias, marigolds, those are some of the common annuals. Abelmoschus. And the plant kind of lets you know when it’s done blooming, it’s starting to turn a little bit brown, looking a little bit dry. And it’s shorter days, cooler weather, those are all indicators to start looking. Morning glories are another, the vining morning glories.

And they start looking a little tattered [laughter], like they’ve done their big show for the season, and then it’s time to harvest. And you want the seed pods to be ripe, but not ripe enough where they open up and a lot of plants will expel their seeds and kind of open up and shoot the seeds around. You want to wait before that happens, or else use some kind of a net bag or something like that to hold the seeds, catch the seeds.

So commercially, we go out twice a week and do the rounds to all the seed plants that we’ll be collecting. And usually we’re right on top of it.

storing bulbs and bulb-like things, tubers, and so forth, and we can talk about those in a second. But I said, “Oh, yeah, when I store my Canna musafolia, or Canna ‘Grande’” [above], and you like interrupted me, you’re like, “You have that? I think that came from us.”

Dennis: [Laughter.] Yep.

Margaret: And you don’t have it anymore.

Dennis: Right, yeah, we … with the mosaic virus we had to get rid of our stock and so I’ve been looking for it, so-

Margaret: Well guess what?

Dennis: I’m still waiting for that package to come. [Laughter.]

Margaret: There might be a package heading south. Yes, there might be a package.

Dennis: Great.

Margaret: I’ve been collecting sturdy boxes since we spoke. And that’s what I love about horticulture, really, is like the remembrance of where every plant came from, like you just said that roadside weed with the silver leaves in Costa Rica—the provenance. And do you know, that sort of sense of … Dan Hinkley and I were talking about this recently because of his book about his garden at Windcliff-

Dennis: Right.

Margaret: …on a recent program.  And how he walks around every morning in the garden and he sees his friends’ faces, because of the plants. You know what I mean?

Dennis: Yeah, that’s so true.

Margaret: You must have that, too.

Dennis: Yep. We have a lot of plants from the original Heronswood Nursery. And some of them even have those little blue labels sticking out of the ground.

Margaret: That’s so funny, because that’s what I started when we did our interview recently, I said to him, I did the intro and said, “Every year when I do my spring cleanup I find turquoise plastic labels in my garden.”

Dennis: [Laughter.] Right.

Margaret: Yeah, so we’re all just one big, happy, crazy family.

Dennis: Yep.

Chondropetalum, a grassy plant, and a lot of the Restio. You know what else is interesting, is if a plant is grown at a higher altitude then a lot of times it can take cooler weather than you would think, even if it is a “tropical” plant.

Margaret: Right.

Dennis: It’s much cooler up at higher altitudes.

Margaret: Right. And compared to trying to push them in the low-light season here in the north, push them to keep growing, to stay active, it’s more merciful, really.

Dennis: Yeah. Let them rest.

Margaret: To let them slow down. Right?

Dennis: Winter rest, yeah.

Margaret: Right. Even if like the phormium they have foliage, and so they don’t want to be in the dark in the cellar with that Pelargonium, the fancy-leaf geranium we were talking about. Or the tropical hibiscus, that’s going to be leafless, or the Brugmansia that are going to defoliate, right?

Dennis: Mm-hmm.

Margaret: So not like that. But also not warm and actively growing and being watered once or twice a week, etc. It’s like we’re backing off on everything and letting them just hover in a way, some of them.

Dennis: Right. I have like a covered porch that you would want to use for three seasons, and then in the fourth season you can store plants in there sometimes if it isn’t going to freeze, or you just put in like a minimal little heater or something just to keep it above freezing. And sometimes that’s all you need, and it’s a nice, sunny porch, but … Or if it’s attached to a house, sometimes that even makes it warm enough. You just open the door and let it warm up.

Margaret: I had an insulated garage and there was a window that was on the bright side, and for some reason those phormiums just … It was super-cool, but there was plenty of light and they just did so much better than where I tortured them in the past. So you know.

Dennis: [Laughter.] Yep, yep.

Margaret: So people may be looking outside now or soon, depending on where they live, and like, “Oh, the dahlias got frosted. Oh, the cannas got blasted with frost.” And they think that’s it. But it’s not it, is it?

Dennis: No, it’s-

Margaret: Those are some of the easiest, right?

Dennis: Yeah, that’s the signal that it’s time to harvest, especially dahlias. Because they’re such … usually, most of them are just late-season and they enjoy this cool weather. Like right now our dahlias are going gangbusters, in full bloom, and we’re getting big bouquets every day. And then after we have our first killing frost, where it’s down below 32, and then the foliage will turn brown or black, and the plant might even get a little mushy, but you dig it out and cut it off leaving about an inch or 2 of stem, and then you have all the bulblets hanging out like fingers almost. And just keeping them, and then actually packed into crates or bags with either mulch, or hay, or peat moss, or wrapped in newspaper, there’s so many different techniques like that.

Margaret: And do you dry them first; do you sort of cure them first a little bit?

Dennis: Yeah, yeah, we let them air-dry for a couple of days. And then again … It’s almost like I tell people to think about it like overwintering potatoes. If you have like a root cellar, you’re trying to mimic the root-cellar condition, a dark and cool but not freezing. [More on stashing bulbs and tubers.]

Margaret: So 40s maybe.

Dennis: Potatoes will last for a long time, and if it’s too warm you’ll see they’ll start growing. So it’s the same thing with dahlia bulbs. Or cannas, Eucomis.

Eucomis [above] are funny, they’re the pineapple lilies. I had bought them over the last … They’ve become sort of a thing, a popular thing, increasingly so, and you have a lot of nice selections with pretty leaves, purple leaves or spotted leaves or whatever, besides the flowers. And I’d always just drag the pots in. I’d have them in pots and I’d drag the pots in because I’m in Zone 5 so they aren’t hardy in the ground. But the pots, it’s heavy getting them into the basement, all that, and I guess could I unpot more of these things? I mean, I guess I could unpot them.

Dennis: Yeah, those could be … Because they are hardy into Zone 7 and occasionally in 6 with some mulch, but they could be bare-rooted and again put into a net bag or a crate or something and stored that way.

Margaret: So in like bark mulch or something like that?

Dennis: Yeah, bark mulch, straw, hay, hulls, sometimes there’s rice hulls or even packing peanuts. If you have a box with packing peanuts, you get a shipment in with something, that works.

Margaret: Now I’m saving those to ship you the cannas. [Laughter.]

Dennis: I’m going to keep my eye out for that.

Margaret: Yeah. So do you … O.K., so say I have the dahlias and I’ve let them get frosted. And I’ve cut them back and I’ve dried them for a few days or a week; I’ve let them cure a little bit. And then I’m going to pack them. Is it important to keep each clump of tubers or tuber separate, like not just throw them in a big pile together in the packing material? Should there be packing material between each one or do you wrap them in newspaper first, or any other sort of tricks, and then like check on them?

Dennis: It’s really what you have time for and how you’ve had success. We’ve done it both ways: individual wrapping, again, something really important with dahlias is labeling if you need specific colors. But I always recommend trying something, and if it works then just keep doing it. If you’re doing something right, like your Phormium, you finally found something that worked for it, and then try some other plants maybe that would fit into that category and make it easier for yourself. You don’t want to make it too much of a chore.

Margaret: Right.

Dennis: Sometimes we’ll divide them all, spray them with antidesiccant. Well actually we let them dry and then spray with an antidesiccant, and then wrap them. But that’s … we’re trying to keep as many as possible for as long as possible, too.

I think cuttings, that’s another way to go out and just start taking cuttings, you don’t want to wait too late in the season for that, but that’s another great way of overwintering plants for some of your favorite plants.

Margaret: Like coleus.

Dennis:  [Laughter.] Yes. Yeah, coleus is very easy, root right in water.

Margaret: Yes. And those sweet potato vines.

Dennis: Yeah, yeah. Like salvias, some salvias, begonias, impatiens. There’s a lot of things that you can root in water.

Margaret: Yeah I wanted to spend the last couple few minutes I wanted to know are there some … You have 1,600 kinds of plants in the list right now. And by the way, people can’t order from you as individuals, but you do ship [to retailers] in the mid-Atlantic and Northeast and so forth, and from like Maine to Maryland. And you have a list; I’ll give the link to the list of retailers on your website.

And I’m just going to say out loud to people: I go to my garden center in the offseason and I say, “What are you ordering from …?” I ask them about things that I want that are on a wholesale list like yours and nudge, nudge to order a tray of something.

Dennis: Oh, sure.

Margaret: You know what I mean, it’s O.K. to ask our garden centers to think about specific items, right, that they can get from wholesalers that we can’t? So-

Dennis: Right.

Margaret: …be bossy.

Dennis: We do that a lot, we’ll get a special order from a garden center specifically for a client. So that works well.

Margaret: So don’t be afraid to do that, everyone listening. Because it is possible, and the garden center is still going to make the markup, it’s not like you’re inconveniencing anybody. So anyway… But are there some, in the last minutes, are there some hot tropicals or unusual annuals that you’re wanting, craving, besides the canna that I’m sending back to you [laughter], that you’re wanting to find that add to the palate, is there like a thing right now that you’re after? On the hunt for?

Dennis: Oh…

Margaret: You have everything.

Dennis: Yeah. Yeah, there’s a lot. I really like colorful foliage. Or variegated foliage; I just love variegated foliage. And just oddball things. I’ve been collecting for myself now just a lot of caudiciform plants, with like big, fat bases on them.

Margaret: Yes.

Dennis: We do offer a few. I know this-

citrus in pots

  • figs in pots
  • rosemary
  • more tropical stuff
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