abuzz with gorgeous umbels, with sam keitch of pennsylvania horticultural society

I THOUGHT MY obsession with Angelica blooms was a serious one until recently, when I met Sam Keitch of the Pennsylvania Horticultural Society, who takes it one step further.

Sam has a passion for various other garden-worthy, umbel-shaped flowers—not just various Angelica, but other plants in the Apiaceae, the family related to carrots and parsley. That’s Selinum wallichianum, above, at 7 or 8 feet tall.

Sam Keitch is Project Manager for Public Landscapes at the Pennsylvania Horticultural Society in Philadelphia, where he creates ecologically driven designs, often in urban settings, enticing pollinators and other beneficials to enjoy the gardens as much as the many human visitors do.

Read along as you listen to the March 28, 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).

unusual umbels for the garden, with sam keitch

Margaret: Hi, Sam. Before we get started on umbel and so forth, PHS is probably best known for its annual Philadelphia Flower Show, but there’s lots of other programming, too. You do public landscapes, and so there are public gardens and all kinds of outreach programs, right?

Sam: Correct. The public gardens and landscapes department works throughout the city of Philadelphia. We’re involved on the historic parkway with the Philadelphia Museum of Art, The Rodin Museum [photo below], The Navy Yard, as well as Subaru in Camden, so we manage a bunch of different gardens and I don’t think people realize the extent of our impact. We’re all over.

Margaret: Yeah and lots of other really important programs supporting education and so forth, but again, people know about the flower show, which is coming up in…

Sam: Right.

Margaret: …not too long, right?

Sam: In June, yeah, early June.

Margaret: In June. So: Ecologically driven design, you tell me, but in an urban setting? What the heck is that going on [laughter]?

Sam: Right. My background is in native plants, and I went to school for landscape architecture, but with our department, we get to experiment. We get to plant really… not necessarily exotic plants, but rare introductions. We get new genetics as well as the tried and true.

Urban ecology is something that’s unique. I wouldn’t think of it in terms of restoration, but we plant things that host wildlife, so when we see insects present, we think that we’re doing something beneficial. The carrot family is one of the families that’s not necessarily all native, but you see the activity with the plants, the species. So…

Margaret: You sure do. It’s pretty amazing when I have a lot of Angelica gigas [above], the Korean Angelica, a biennial in my garden. Literally I can stand next to a few of the flower heads on one big plant, and I could stand there for an hour and not one of the bees or wasps or anybody who’s on it, cares a lick that I’m there. It’s like they just don’t even look at me [laughter]. They’re so happy.

Sam: It’s overwhelming. You’ll see bees, wasps… Everything is just there on one flower head. And I think people think of certain native flowers or pollinators and… but all the angelicas, and other species in the Apiaceae, they’re all pretty active. So they’re easy to propagate for us in the urban environment, because they’re so easy to propagate in a controlled manner, we can thin them the first year, since most are biennials. There’s no chance of them escaping. So…

Margaret: Right, so we’ll talk about that. We’re going to get some of your tips for how to manage biennials and get them going, and your propagation hints and so forth, because it confounds a lot of gardeners, but first who else is kind of in this family that you love, what other genera of plants? We’ve talked a tiny bit about the angelicas, but there’s lots of other possibilities, right?

Sam: Yeah, there’s a lot of really fun species. In this area, there’s a lot of different public gardens, and sometimes we’ll get a few seeds or a plant. Seseli gummeriferum, the moon carrot, and we’ve been planting it.

Margaret: The moon carrot! [Laughter.]

Sam: Yeah, the moon carrot and it has the silver foliage. We plant at the Rodin Museum, and it is reliably coming back for us, so that’s, exciting. There’s so many to depict, but I think of the cut-flower ones, the Ammi ‘Green Mist,’ and then, Daucus carota ‘Dara.’ Those are kind of… They’re in the cut-flower scene, but we use ‘Green Mist,’ which looks like a larger Queen Anne’s lace flower, so…

Margaret: Right. Right.

Sam: Yeah. It’s a great filler plant, and we put it in the mid-border and it’s just very easy.

Margaret: I see that Johnny’s Selected Seeds and Select Seeds (a wonderful flower seed catalog and flower seedling catalog)… Both of those sell the ‘Green Mist’ Ammi. I think ‘Dara’ also, the Daucas carota—doesn’t it have dark stems and flowers?

Sam: Yeah. It’s a darker head, and there’s also one called ‘Black Knight’ [above], so a lot of the Johnny’s and different seed companies will sell all three of them.

Margaret: So what else is in here? Seseli, you said, the moon carrot. I have to find out about moon carrots [laughter].

Sam: Some of the coveted ones that I’ve always wanted was the giant fennel, Ferula communis. And there’s also one called, Peucedanum verticillare [giant milk parsley], and a gardener at the Scott Arboretum gave me just a few seeds.

Over the years, I’ve kept collecting them, but Peucedanum is… Structurally, it’s a much larger plant. It’s very tall, so it’s not for every garden, but Peucedanum is a larger Selinum, which is another genus, Selinum wallichianum. The ones that I have in my garden are probably 7 or 8 feet tall.

Margaret: Whoa.

Sam: Big plants.

Margaret: I’ve seen the common names of that as hog fennel or milk parsley, who the heck knows, and with that one, I see that sometimes you have to buy a plant. Well, actually, I saw that Plant World Seeds has some seeds, I think, but Plant Delights Nursery and Digging Dog Nursery both sell plants, so you could get a young plant and let it sow itself and so forth.

So you said a fennel… So there are other kinds of fennels, too, I suppose, right?

Sam: Now I would have to put out a disclaimer. Bronze fennel—it is a beautiful plant. We have used it in our sites, but you have to be very careful with the seeds, and the same goes with dill and a lot of different ornamentals—even the edible or culinary plants. I would just stress that you’ll learn your lesson when you let it go to seed, and the next year, you have hundreds of fennel plants popping up, so be very careful [laughter] about them sowing in your garden.

Margaret: It’s true. What about the… is it Anthriscus, the chervil relatives?

Sam: Anthriscus. There’s ‘Raven’s Wing,’ which is another kind of naturalizer, and we’re trying to establish it. We’re going to contract,-grow it, to plant it within these little niches along the walkways. It kind of thrives in indirect light, so a lot of the ones that we’re talking about that are biennials… They like sharp drainage or full sun. Anthriscus thrives kind of in that less-intensive area, so we’re going to put it along the walkways and ‘Raven’s Wing’ has this darker-tone foliage, which is really gorgeous.

Margaret: Right. Again, when you say biennials to people, or short-lived perennials—things that we want to have self-sow and again, we’re going to talk about controlling some of them—but a lot of gardeners are like, “Well, I got a plant and now I don’t have anything flowering this year. I got a plant last year.”

Well, O.K., that’s because it’s a biennial.

How do we get started and how do we… A gardener at Wave Hill in New York, the public garden in New York, told me years ago that they would sort of mark off areas around the sort of mama plant where they wanted the babies to sow, and make sure not to rake too much there or mulch too deeply there. To kind of to make these zones, these safety zones, for the biennials to sow into and so forth. You have to be conscious. Tell us a little bit about how you manage them and propagate them and get them going.

Sam: I learned this trick because I garden with my father, and he weeds everything. When you germinate Angelica or any of the biennials, the first year, it’s this really insignificant trifoliate set of leaves. And so when I placed them around the property, they would get weeded. But I started germinating them in bulb crates. You can do them in containers, traditional flats, but I like to just sprinkle them on a bunch of compost or potting soil in a flat, and I’ll use a thin layer of gravel mix on the very top.

After the first year, they’ll send down a taproot when they go dormant again, so the trick is transplanting the young juvenile plants early in their life cycle and during the first year. I plant a lot of them, and then I thin them later, but I do mark the location with other plants and bulbs as well: Colchicum, the fall-flowered ones; different spring ones, and having an arrangement in each location that will remind you, this little guy is here.

And people don’t believe the display the following year. They don’t think those little leaves are going to become this huge, structural inflorescence. So…

Margaret: Right. Right. The Angelica gigas, the Korean angelica at my place, it loves, of course… A lot of the biennials and self-sowing annuals and perennials love to sow into the cracks and crevices [laughter].

I tend to go around, and I see them, tiny little guys like you said, with these three-part leaves. And I know who they are, and I go with my little hori hori knife, when it’s moist in the early spring. I get a wedge out of the crack, and put them in a tray, and I walk around the garden and I put them where I want them to be.

I create the pictures with them. They provide plants for me, the mother plant does, the previous generation does, but I move them around, so it’s kind of like what you’re saying. So you actually collect the seeds and sow them intentionally in a more controlled environment and then move those babies. Yeah.

Sam: Yeah. You can do it both ways and I think it’s nice when it kind of naturalizes, but you just have to keep in mind, it’s the next year. Sometimes, they’re so subtle, you miss them. But if they naturalize, the Angelica gigas—it’s such a beautiful plant, that if it seeds in, I usually let them go and then thin them the following year, because it’s worth it.

Margaret: Right. I find also the ones that get the most statuesque—and some of them get quite big, like way over my head, with many, many, many arms, like a big candelabra crazy thing. The ones that get the biggest are the ones that sow themselves, that I didn’t disturb that taproot, even when it was young.

Sam: Yeah, the taproot is… It’s funny, I remember somebody asked me for smaller plants, and you don’t realize how deep it is. It gets really deep. When you get a transplant, you’ll get the tricks down. You’ll play it by ear, but if you actually try and transplant them with the taproot, it won’t work. You’ll figure out the timing.

Margaret: O.K. The garden centers are going to open before long and you know, people are going to go to the garden center and sometimes… The first moment I saw this, I was horrified. I saw my beloved Angelica in a big pot, a blooming-sized plant, like a second-year plant, because again, these are biennials. It doesn’t bloom in the first year. It blooms the second.

It was like 20-something dollars or something [laughter]…

Sam: Yeah.

Margaret: …and I thought to myself, O.K., the poor person who brings that home is going to have this fabulous thing for a minute or for a month or whatever, and then next year, isn’t going to have any.

Sam: Right.

Margaret: They’re going to wonder what they did wrong. What should we do if we want to get started with biennials? Should we get a plant and some seed, or what do I have to do?

Sam: Yeah. That’s the thing. That might work for some people, but what I would do, if they did take that home, is collect the seed, because the seeds remain viable.

I think with biennials, it’s really a seed game, and planning ahead, so you can stagger the sowings each year. But that person could bring that plant home, let it go to seed, collect the seeds when they’re dry and store them in the refrigerator, or germinate them that year.

I really think of this as one of the most efficient families, because when you grow things from seed, it’s just more about foresight than effort. It’s just about placing that seed in a little bit of material, and you’re good to go and then remembering. It’s all about planning.

With very little effort, you get these incredible displays. For me, it’s one of the most dynamic families. You can just put this little plant, and it’s dormant for the first year, it’s kind of tucked away, and then the next year, it surprises everybody.

Margaret: Right? The one thing that they’d also have to do, if they wanted flowers next year, is buy another $20 plant [laughter].

Sam: Yeah. Don’t do that. Yeah. Sow the seeds consistently.

Margaret: Yeah, but you won’t have any Year 2, do you know what I mean? You have to wait, you’re going to skip a year, right?

Sam: Don’t go out and buy Angelica [laughter]. That’s the lesson.

Margaret: Right. $40 later, two plants later, you might get started, but yeah.

Sam: I have to say, when you collect the seeds, you’ll see there’s other angelicas out there. That’s the fun part is finding different sources of seed. It can be tough, but we have a native Angelica. There’s Angelica atropurpurea, there’s Archangelica… There’s so many that are out there that shopping for seed and getting them is as fun as sometimes germinating them.

Margaret: There’s another one that I tried. It was like a few years ago. It was like the next best new thing and I can’t remember which one it was. I don’t know if it was atropurpurea or which one it was.

Sam: Yeah, there’s ‘Ebony’ as well, and so [above, coming into bloom with its dark stems]….

Margaret: I didn’t do so well with those.

Sam: We’ve been growing Angelica ‘Ebony’ and it’s a darker, fuller tone and it’s beautiful. It has kind of a smoky pink flower, but there’s Angelica stricta purpurea, and that is kind of a really… It’s very dynamic. The flower is kind of changed in tone, and it is gorgeous. I would say it’s tied with Selinum in terms of… It’s very elegant. Those tones are rare, and they’re very elegant.

Margaret: What about the control? We talked a little bit about the control. We have to be observant. And I have, what I call the national collection of dill [laughter], because I have dill everywhere. If I—other than the seeds that are in the ground that would still be good for a number of years in the future—if I deadheaded all the dill, if I didn’t let any of it go to seed, I could reduce that. I used to have other things that did that, and I gradually got ahead of it.

We’re going to collect our seed that we need for propagating and so forth, but are we deadheading? We are maybe avoiding growing certain ones?

Sam: Yeah, I would definitely. I let my plants go to seed, but typically, I’ll actually collect the seed, so I’m not worried about them becoming rampant. I think people should get to know the species, grow one plant. Also, if you know your soil… I find that these typically germinate much easier on looser soil. You have sharp drainage or gravelly soil, I find that they’re much more prolific.

Especially fennels. If you have loose soil, sharp drainage, beware, don’t let them go to seed. It’s more about the cycles. You want to collect them for propagating, but you also want to control them and I think it was Stephanie Cohen who talked about how you should just let Angelica… If you’re lucky enough to have it propagate, let it go, because it’s so beautiful.

I did that over a few years and eventually though, it became like Angelica land [laughter]. It was just in every bed. My dad loved it… My garden… I kind of control it. I kind of have it as a central element. You have to be careful. You do have to monitor your garden. That’s just part of gardening. I would recommend deadheading, first and foremost.

Margaret: Right. Some of these other ones… I’m totally enchanted now, of course, not just the other angelicas, but like that crazy-sounding Peucedanum. And the Selinum that you’ve talked about, by the way, I saw that a couple nurseries, including one that I don’t know in Maryland, Putnam Hill Nursery. Have you ever heard about that?

Sam: I don’t know it.

Margaret: Yeah, they have plants, and Annie’s Annuals out in California, they usually have it. She loves it, but it’s out of stock right now when I last looked, but I bet it’ll be back again. They are available, and sometimes you have to wait to get a start of some of these more unusual things, right?

Sam: Right, right. That’s another species that… You’ll see it here. You’ll share it with friends, but I only know a few gardeners who had seeds. It’s something that I’ve always kind of lusted after. I’ve always wanted it. The leaves are unique. As you start to collect the different species, the foliage just has different… It’s cut very finely.

Those different characteristics, you want them in your garden, so I’ve been searching for it for years. It’s often hard to find seed, and when you do, it becomes very rewarding.

Margaret: Huh. Well, maybe you’re going to have to buy one of these baby plants and grow it out for seed [laughter].

Sam: Or you can share it with me. Maybe we can share the seeds.

Margaret: Uh-oh. This could get really dangerous [laughter]. My angelicas will be very angry if I let anybody else in, I think, because they are the star for July to September, right.

Sam: [Laughter.] Right.

Margaret: I just want to ask you… I know that obviously you don’t just use umbel-shaped flowers in your gardens. Another big hit there, is the composites, the daisy family…

Sam: Yeah.

Margaret: …and those are big attractions for people and for beneficial insects, aren’t they?

Sam: Yeah. The composites: That’s just a massive topic, but we have…

Margaret: I just wanted to get people to paint a visual picture of some of the diversity that you’re working with in these ecologically driven designs.

Sam: Yeah, we have dozens of different daisy family species in our designs and different roles. They are really kind of woven into our sites. If you visit Philadelphia, you’ll see Rudbeckia ‘Autumn Sun,’ different rudbeckias. And we trial everything, so we have the opportunity to just plant them in different settings throughout the city.

One of the best examples is Eastern State Penitentiary [below, one garden bed there]. If you go there, we have dozens of rudbeckias up there with different grasses. We have Sorghastrum nutans and rudbeckias. Very simple, and it’s just one of those demonstration gardens in the city to showcase the urban context.

I love when people visit our sites. We have volunteers, but PHS does so much, and it’s getting people involved, so I invite anybody to come out to the penitentiary and help me plant more plants, but…

Margaret: So you do have volunteers, don’t you?

Sam: Yeah. Yeah, we do.

But that’s one of the families… That’s everyone’s favorite. Midsummer, after the heat picks up, some stuff looks kind of tired, and the rudbeckias pick up and they bloom for a very long time. But there’s a ton of different species in that family. So…

Margaret: In the last couple of minutes, anything in your home garden? Are you coveting or have you acquired anything new for the home garden this year? Is there…

Sam: Oh, this year? I think my favorite thing is I finally bought Gladiolus ‘Boone,’ which is a hardy Gladiolus.

Margaret: Oh.

Sam: That’s what I’m most excited about. It’s shorter in stature, it’s hardy, it’s almost like this peach tone. And I have it with Sanguisorba ‘Blackthorn’ and Eragrostis elliottii, which is left over from last year’s flower show. I’m excited that the combination is… It’s different, and that’s what’s fun about it.

Margaret: Any new umbels this year at all?

Sam: Seseli—it’s the first time growing it at home [above, a macro photo of the many umbels within a flowerhead of Seseli].

Margaret: Oh.

Sam: The public PHS sites, we’ve planted it, but I’ve never grown it at home. I’m trying to gauge how fast it will… What role it’s going to have in my garden.

Margaret: Well, it’s very interesting. I’m kind of excited about all of these. And Orlaya—I didn’t even know that genus, so I’m like, “What the heck is that?”

Sam: And that’s one of those cyclical plants. I thought of it as an older plant and it kind of became in vogue, because one of the public gardens in our area grew it. And people became really excited by it, but it’s such an easy plant to sow. I knew it from cut flower fields long ago. Things come back in style and yeah, Orlaya is one of the new favorites.

Margaret: Yeah, exciting. Well, Sam Keitch of the Pennsylvania Horticultural Society, I’m so glad to talk to you and I have a feeling we’re going to be having more conversations before long, so thank you so much.

Sam: Yeah, thank you so much for having me. I had fun.

(Plant portraits by Sam Keitch; public-garden project photos from Pennsylvania Horticultural Society.)

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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 11th year in March 2020. In 2016, the show won three silver medals for excellence from the Garden Writers Association. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the March 28, 2022 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify