flowers that stand up to the heat, and growing lavender, with jenny rose carey

HOT AND DRY: That’s the lament of gardeners in most regions in high summer, and also of many plants in their flower gardens. The author of a new book called “The Ultimate Flower Gardener’s Guide” is here to suggest which perennials can stand up to the test best—plus give us some lavender growing advice, speaking of plants adapted to hot and dry.

Also on the agenda today, a tip on a bulb you may not have grown before, but could order to plant this fall, surprise lilies. Above: giant knapweed (Centaurea macrocephala) and rattlesnake master (Eryngium yuccifolium) in her dry garden.

Jenny Rose Carey is former senior director of the Pennsylvania Horticultural Society’s Meadowbrook Farm and taught in the Department of Landscape Architecture and Horticulture at Temple University, where she also directed the Ambler Arboretum.

Plus: Enter to win her new book, “The Ultimate Flower Gardener’s Guide” (affiliate link), by commenting in the box near the bottom of the page.

Read along as you listen to the Aug. 15, 2022 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).

the hot, dry flower garden, with jenny rose carey

Margaret Roach: So tell me what you’re seeing out the window. Where are you? You’re in Pennsylvania in your 4.5 acre garden, are you?

Jenny Rose Carey: I am. My office is on the third floor, so I get a bird’s-eye view out into the lovely moon beds with Phlox and my herb garden and my dry garden out the window. So it’s lovely.

Margaret: Nice. That’s funny. I’m the same way. For me, the garden experience is about looking out the window because nine-tenths of the time, that’s how I perceive the garden, right? Except when I’m working in it and crawling around [laughter].

Jenny: Yeah. Then you get the worm’s-eye view from there.

Margaret: Correct. Correct. Yeah, exactly. So in the book, whether for dry or average or moisture gardens, any kind of conditions, I loved how at the beginning of the book, you really encouraged readers to choose their plants, not just for the cultural conditions, but for the aesthetic. Like a range of shapes and sizes to play different roles in a successful design. And that’s a really helpful part of the book, I think. So just, in brief, can you give us the elevator pitch of when we go shopping again in the catalogs for fall or in the garden centers [laughter]?

Jenny: Sure.

Margaret: Yeah.

Jenny: I think the reason I started off like that, this is my true pandemic book, Margaret. So I had time to really be by myself and think about how I put gardens together. And I find for a lot of people, they begin by growing a few things, but then it looks more like a collection and less like an aesthetically pleasing garden. So I think that’s the bit that people struggle with.

They can probably grow the things, but then it’s knowing how to combine different ones in the same flower bed that look good together, grow in the same conditions, and have seasonal interest for as long as you need that garden to look good. And so I started with shape, because the interesting thing over all my many years of gardening is that people’s opinions on colors really differ. So what looks good to you, what looks good to me, what looks good to your listeners will be different.

But, in general, everyone agrees that a garden that looks really pretty, nice, joyful, has a variety of shapes of flowers, textures of leaves, and heights, not in necessarily serried ranks, but that is pleasing to most people. And then color, that’s where your choice comes in.

But to get people to look more closely at the plant itself, the flower itself, the shape of the flower, and also then I do go off on pollinators, and the pollinators that are loving the different shapes and things like that because, obviously, each flower is adapted for a different pollinator. [Above, from the book, a combination of flower shapes, colors, and heights.]

Margaret: Sure.

Jenny: That comes in, too.

Margaret: Right. So we don’t want all big, bold, or we don’t want all linear, vertical things. We don’t want too much, or everything ferny. We want a mix of things. Yeah.

Jenny: That’s right.

Margaret: Yeah. Yeah, no, I love it. I love it. Yeah. I think it’s such a good reminder and great way to start the book, as I said. Not that, of course, I ever just collect plants and don’t know what to put with them or anything [laughter]. Oh boy. You’ll see.

Jenny: None of us are plant collectors, right? We don’t just go and say, “Oh, I need another one of that one.” Yes. And that’s the trouble, especially as we go towards the fall: Look how many daisy shapes are out there. We love our daisies. They’re cheerful. They remind us of when we were kids and picking the petals off and everything. Very, very nice colors and shapes, but all of the asters, all of the Leucanthemum, and things like that.

So it’s really being aware, when you look at your garden, and saying, “Hmm, there’s a lot of daisies out there. What can I add?” And actually, the thing we’re going talk about later might be a really good one to add in to your full garden, but we’ll save that for later.

Margaret: O.K. [laughter].

Jenny: But just being aware of that, and even if you can’t mix up the shapes, play with scale because some of the asters are very cute, little tiny daisies, and then you get the bigger, bolder, purple coneflowers and things like that. So it’s just getting your eye in a little bit more and being a little more critical of your compositions, I think.

Margaret: Yeah. No, good advice. So we were going to talk about it is the dog days, as we used to say. They’re hot and dry. What’s the driest part of your garden? And give us a little orientation to that.

Jenny: Well, actually, I have quite a lot of dry bits. So I have 4-1/2 acres. When I moved here 25 years ago, there were no outdoor taps. So it was a kitchen sink, a small watering can was my only option. So I really learned right from the beginning to be frugal with my well water. And especially when I had my three girls living at home and there were lots of showers, it was like, “Ah, O.K., girls have a shower, or water something?”

I suppose I’ve always been aware of water. I don’t really know why, but the really driest bits are obviously a long way from any hose, and that’s usually your perimeter bits. Usually around the house, you can get a bit of water to things, but the further you go away from your kitchen door, usually those are drier.

You might have a bit that’s on top of a slope. That would be dry, or you might create berms. I deliberately create bermed raised beds to make them dry because, as we know, certain things love that hot and dry thing. So I have a top of a waterfall, and it’s 6 feet off the ground. And so, obviously, that bit, very, very dry, and baking sun.

So my dry garden, I haven’t watered since 2004. So that one does not get watered apart from the rain and the snow and things like that. And then I have a sunset garden that is a long way away from any hose, and that is sort of modeled on my dry garden, but it’s more of a shape garden, and also I wanted to grow more lavender, which again, we’re going to talk about. So I have a lot of areas that I don’t water that much, really.

Margaret: Yeah. So in the dry garden now, I think I saw a picture in the book, and that has a gravel as opposed to mulch of an organic nature. It has a gravel surface. Is it in deep gravel, or is that just a topdressing of gravel? It’s sort of a gravel garden, but …

Jenny: Well, interestingly, a lot of us plan our gardens in the winter. That’s when we do our, “Oh, I’m dreaming of Provence. We’d been to Provence the year before. It’s south of France, and I am a bit of a lavender nut. I’ve belong to the Herb Society of America for many years in our Philadelphia unit. And so in my herb garden, the lavender was not thriving. So yes, when I went to the south of France and saw lavender growing in amongst road chippings, basically, and I’m like, “Uh-oh, I’m doing this wrong.” So I planned that dry garden to mimic more of the south of France.

Margaret: O.K.

Jenny: So that’s really … Oh, now I’ve forgotten what the question was. I’m sorry [laughter].

Margaret: No, and so it’s inspired by what was on the roadside or whatever.The gravelly fast-draining medium. Yeah.

Jenny: Oh, in my dreams over the winter, I was going to get our natural soil and amend it with tons of grit and gravel and mix it all up and everything like that. But of course, I was on a garden tour for the Pennsylvania Horticultural Society on, I think it was May 18th. It’s ingrained in my memory, and we had the wettest spring ever. So the garden was going in, and it looked like a swimming pool. So no amendment happened. So I bermed everything.

That gives you a sense of enclosure as you walk around the garden, so you just raise the things up, and then the most drought tolerant things go on the top.

The ones that need a bit more moisture go down the bottom, and then I mulch the whole thing with probably 3 inches, about, of small river gravel. And it does roll downhill, Margaret. So you have to sort of push it back up, but the idea is even when you’re planting the hole, it doesn’t matter if gravel goes into the bottom of the hole. That just helps with drainage. So you just clear the gravel away, dig your hole, and also do release the roots a lot if you’re planting in gravel, all that sort of thing.

Margaret: Yes. Of course. So what are some of the, in this particular dry area, this gravel garden that you were just describing, what are some of the … I mean, I think you have California poppy in there. So tell us about some of the stars, and there’s lavender, and we can talk a little bit more about lavender. So tell us about some of the stars.

Jenny: So it’s interesting, because I did my research. My dad is a botanist, I’m a biologist, so I did it like, “O.K., what do I think is going to survive?” Because at the time, nobody in 2004 was really, apart from maybe Beth Chatto in England, in Essex, who we both love … So she was talking about it, but in Pennsylvania, we have completely different climate. So I was looking for, particularly, well, lavender, but I was looking for things that had small leaves, because, obviously, then there’s less transpiration out of the leaves and it doesn’t wilt as much. So small leaves, silvery-gray leaves, and things with a taproot. So I started with some Baptisia.

Margaret: Oh, wonderful. Yes.

Jenny:  And I knew it had a deep root because one of my friends had offered me one, and I’d had to dig it up from her garden. So I’m like, “O.K., you’re going in first.” Then butterfly weed [Asclepias] has an incredible taproot. I knew that from personal experience. So those were two of the early ones. Then I tried a lot from seed because the gravel is a perfect seed bed, and so things like, actually, the butterfly weed didn’t get going until I seeded it in.

Margaret: Oh.

Jenny: Then it really got going. Things like Stokesia.

Margaret: Or they call it like Stokes aster or something like that.

Jenny:  Stokes aster.

Margaret: But yeah, it’s not something that people really … I don’t know a lot of people who grow it, but it’s a great plant, right?

Jenny: Oh my goodness. I would say it’s just finishing flowering now, but I would say that’s one of my top-loved ones that I didn’t really think about. Obviously, things like Dianthus, all of the Dianthus that hate having things laying on top of them, the silvery-leaved ones, seedlings, obviously, because they have the waxy cuticle on the outside. Larkspur does really well in there, by seed.

Margaret: Oh.

Jenny: Obviously, columbine, and particularly the Rocky Mountain columbine.

Margaret: Yeah.

Jenny: That one, early on, was really a star. Armeria maritima, anything with a word like Crambe maritima, anything with the word looks like maritime, because they’re used to growing in gravelly cliffs and rocks and things by the seaside, which obviously dehydrates things. So look for the word maritima. And then many of our American native plants, if you look at those Prairie plants, if you want that type of look, many of them are really, really deep-rooted and they have roots down to 4 feet. So establishment, things like … Oh, I love Rudbeckia subtomentosa ‘Henry Eilers,’ with the quilled petals [above].

Margaret: It’s wonderful, yeah.

Jenny: I just love that plant. I don’t know why.

Margaret: It’s wonderful, yeah. It’s a beautiful one. And they are, the petals are just … You just could stare at them forever.

Jenny: And if you don’t know it, look it up. It’s just the cutest, and there’s a new one called ‘Little Henry’ that is meant to be shorter. We’ll believe it when we see it, because that thing … And I don’t water these things, and they’re still so, they’re just really happy. Any of the bulbs as well.

Any bulbs really do well in there. And when you are designing your garden, you’re going for a look. So I’m English, obviously. So my look was dry garden without looking like a dry garden. My brother-in-law gave me some … We can grow hardy cactus here. I didn’t want that, though. I let it drop off into the compost heap [laughter]. But things like that, I didn’t want that. I didn’t want anything that looked like a dry garden. I wanted a regular flowery cottage-y garden intermingled style that just looked like a regular garden, but I never watered it. And that was my look. So if you like all the spiky … I do have yucca in there, and some other things like that. But I basically wanted a normal garden, but with no watering.

Margaret: Right. You said bulb. You said the word bulb, so let’s digress for a minute into bulb because there was one on the list in your book for this particular area of your garden that you then have a plant profile of elsewhere in the book, which are the surprise lilies, Lycoris.

Jenny: Yes.

Margaret: And I have to say, when I got my garden, when I moved to my place, maybe 35, 37, years ago, the first fall, up came these strange-looking pink things. But there were no leaves. It was like these spikes, these stems came up, and boom, these little pink lily-shaped flowers were suspended, quite a bit above the ground. And I was like, “What are these?” [Laughter.] I think that’s one type. Was that squamigera or something like that [above, from the book].

Jenny: Yes.

Margaret: Some of these names, there’s just no way to pronounce them. And you British types pronounce them differently, you know [laughter]?

Jenny: That’s true. That’s true. We’re divided by the common language, as they say yes. Yeah, oh my goodness. Well, there was your surprise, Margaret. That was your surprise. So they are a surprise.

Margaret: Yes.

Jenny: And even when you have planted them, sometimes you’re like, “What the heck is that? Oh, wait. Surprise!” Another name for them is naked ladies, which obviously is non-PC, though the life cycle of some of these bulbs is that their foliage comes up in spring, and it can look pretty ugly, to be honest, because it’s large and lanky, and basically you want it somewhere that’s not at the front of the border because otherwise that will be like dominating early scenes.

So that is when they do their photosynthesis, when there’s plenty of moisture in the soil, usually in spring, and they put out these long leaves and you’re just like, “Ugh, you’re ugly.” And then you forget about the ugliness because then, at this time of year, they should be coming out anytime now. They’re late summer, early fall in most people’s gardens.

Margaret: The flower stems would be coming in?

Jenny: Yes, the flower stems. So the leaves die down. All of that goodness goes back down to the bulb, and it just sits there, and then all of a sudden, these, as you say, tall shoots come up. And we used to think that they weren’t that hardy, but some of them have ended up being hardier than we thought. And if you give them these gravel conditions, I think that helps them survive because, like most bulbs, they hate winter wet.

And particularly, here in the mid-Atlantic, we get not a good snow cover, we get that freeze-thaw, we get wet periods over winter, and that can be when a bulb could rot, or if you irrigate. If you have an irrigation system, which I’m not a big fan of, if you have an irrigation system, often the bulbs, like even a daffodil, might rot in the summer. So they need relatively dry conditions when they’re in their dormant phase.

Margaret: Yes. It reminds me, the lifestyle, the life cycle that you described, where you get the foliage and then that disappears, and it’s quite a while and you’ve forgotten about them, and then, “Oh, there it is,” it reminds me of Colchicum, the so-called autumn crocus that are not-

Jenny: Exactly.

Margaret: You know what I mean? It’s another thing that’s like, “What’s that? Oh my goodness, all that foliage,” and then goodbye, it fades away [laughter]. And then yeah, and then in the fall you get this. That’s a surprise, too, but on a smaller scale.

Jenny: I agree. And there’s another one. So there’s several that I would recommend to your listeners. Lycoris. All of the different Lycoris, and they come under these various names. So you’ll just look for ones, and look at the zones, and then maybe push it half a zone or a zones, if you have a sheltered position.

The other one, apart from Colchicum, which do the similar thing, is Sternbergia, and these are the fall daffodil, and they don’t look like a daffodil, really. They look more like a crocus, I suppose, a big crocus. But they’re yellow. They’re bright yellow, like a daffodil would be, and they come out … They’ll be out maybe September in our climate, and they’re another good one. But the leaves, again, come up in the spring. They die down, you forget about them, and then all of a sudden, they come up. And I have that in my sunset garden, and they’re just a … If you are trying to extend your season, have something different, look for Sternbergia. I can’t remember … Oh, fall daffodil, I think it’s name is. I’m not so good on the common names. But-

Margaret: No, me neither. You mentioned the freeze-thaw, freeze-thaw, wet feet in the winter situation as being inhospitable to the bulbs. And getting back to the lavender, that’s also inhospitable to the lavender, or for that matter, the other silver foliage plants that you talked about that might be good in a garden like this, like Santolina, for instance, or whatever.

They’re going to get that root rot and just drop dead, as opposed to survive. So let’s talk again a little bit more about lavender. You mentioned it earlier on, but about being inspired by that rubble-y medium that you saw them thriving in. Are there particular varieties that are easier to grow that you have found easier to grow?

Jenny:  I think in our climate, the English ones [Lavandula angustifolia] are easier, and if you’re going to be using them for cooking, you can put them into lavender cookies and things like that, or make a simple syrup, if you’re a herbal person. Those are, I think, less medicinal tasting. And never overdo it. A little bit of lavender goes a long way. I had some lavender chocolate that made me want to throw up. So just saying, it’s not that … You have to watch it.

So there’s two main ones that you’ll find very easily. One is named … They’re both named after English gardens. How about that? So one is named ‘Munstead’-

Margaret: For Munstead Wood, yeah.

Jenny: Yeah. Gertrude Jekyll’s garden. And then one is called ‘Hidcote,’ Major Lawrence Johnston’s garden, National Trust Garden, in the Cotswolds. Now let’s take the Cotswolds for a minute. That is a lump of limestone, and limestone is alkaline. So the underlying geology in that area of the country is … I think it’s oolitic limestone, but it’s limestone.

And then when you look at the south of France, if you look up Les Baux, oh my goodness, it’s the most gorgeous place. It’s near where Van Gogh went when he was in his hospital, and you can see his olive trees and his irises and things.

Well, you look at that area, lump of limestone. So I used my eyes and thought, “O.K., I’m in Pennsylvania. We have slightly acidic, neutral to acidic soils.” So what I do is raise up the beds, make the beds face the sun as much as possible. And when I’m talking about raise, in my sunset garden, my lavender bed is, I would say, a couple of feet off the ground at the back.

Margaret: Wow.

Jenny: Yep. I mean, it’s a slope, and then you mulch it with gravel. And if you don’t want to do that, you put chicken grit, turkey grit around under the lavender to reflect the heat and light. They really dislike that wood mulch.

Margaret: Yes.

Jenny:  It holds too much moisture underneath it, and if a stem flops, which it always does on lavender, it just rots, as you were saying. So limestone, I add … In the same way as you might do your veg beds, just a gentle amount, not overdone. So I just gently lime the soil, usually in the spring. I have these raised beds I mulch with gravel or grit or anything you can get hands on that is inorganic, inorganic mulch, and several inches of it. Not just a little bit.

I plant it slightly proud of the surface when I plant it, so it’s not deeply planted. And the other thing is that these are sub-shrubs, so they’re like a shrub, but they’re a herbaceous sort of in between. So you can trim after flowering or when they’re in the bud phase to use the lavender and harvest it for lavender wands or whatever you’re making, or just potpourri type things. But then do not prune it in the fall.

Margaret: No.

Jenny: And I have known more people kill their darn lavender by saying, “Oh, I just gave it a nice autumn haircut,” [laughter] and then it doesn’t come back. So I wait and wait and wait. It looks so ugly. It’s like in the spring, you’re just waiting for this to look better. But I wait until two, three, four shoots have started to grow before I trim it back, because then you know where it’s died back to.

And then the other thing is, what I do on my lavender bed, every year I had one or two new ones, because the oldest ones will die after a while if you haven’t given them exactly what they want. So don’t be worried about that. Just keep on adding another couple, another couple. And in our climate, I would suggest trying not to do a straight line of one type of lavender, like an allee down a path type thing, because otherwise, it looks like a gappy-tooth thing when one of them dies.

Margaret: Really quickly in the last minute, just tell me … Confess: What’s the newest plant you either just got or that you’re hunting for right now, even though you have a lot of plants [laughter]?

Jenny: Oh my goodness.

Margaret: Is there something?

Jenny: Oh, it has to be bulbs right now. I’m thinking about spring and all the yummy … I’m going to do a whole bunch of different tulips in pots this coming year.

Margaret: Oh, nice.

Jenny: And I’m really looking forward to that, but I did see one. I was just at the Perennial Plant Conference in Lancaster, and I just saw, I’m looking up on my Instagram right now, because it was just the best, and it was a … I think it’s called ‘Bellissima’ by Hort Couture, and it is a … You know ‘Kent Beauty’ oregano?

Margaret: No.

Jenny: Oh, O.K.

Margaret: Uh-oh.

Jenny: Well, that’s one of my favorite oreganos, and we’re using it everywhere, and there’s a new one that’s slightly smaller in scale, and I just am loving it.

Margaret: Oh boy. All right.

Jenny: Just an ornamental oregano.

Margaret: O.K. Well, thank you. And thanks for making time today.

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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 13th year in March 2022. 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 Aug. 15, 2022 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify or Stitcher (and browse my archive of podcasts here).