Monticello's gardens are a living expression of Jefferson's genius and his distinctly American attitudes. Graced with nearly 200 full-color illustrations, this book by Monticello's former director of gardens and grounds explores topics ranging from enslaved labor in the Monticello gardens, garden pests of the time, and seed saving practices.
In this episode of "A Rich Spot of Earth" we talk vining plants, self-sowing annuals, and trees that flower in the summer. We also tackle a less pleasant topic: weeds and what to do about them.
Featuring Michael Tricomi, Interim Manager and Curator of Historic Gardens; Peggy Cornett, Curator of Plants; Debbie Donley, Flower Gardener; and, Robert Dowell, Senior Nursery Associate at the Center.
Michael Tricomi: It's June here at Monticello and it's a beautiful time of year to be outside before it gets hot and humid.
This month, you can see roses, purple coneflower, and English lavender, and the flowering Catalpa tree on the mountaintop. In the vegetable garden, we’re harvesting strawberries, radishes, cabbage, kale, broccoli, swiss chard, lettuce and peas.Today we’re going to talk about vining plants, self-sowing annuals, and trees that flower in the summer. We’re also going to tackle a less pleasant topic: weeds and what to do about them.
This is “A Rich Spot of Earth,” a podcast about gardening and the natural world. I’m Michael Tricomi, Interim Manager and Curator of Historic Gardens at Monticello, Thomas Jefferson’s home in Albemarle County, Virginia.
Today we’re going to talk about vining plants, self-sowing annuals, and trees that flower in the summer. We’re also going to tackle a less pleasant topic: weeds and what to do about them.
Flowering Vines and Self-Seeding Annuals
Michael Tricomi: Let’s start with flowers. Jefferson grew quite a few climbers and ramblers. I recently sat down with Curator of Plants Peggy Cornett and Flower Gardener Debbie Donley to talk about them.
Debbie Donley: This week I have been really busy putting up structures for the vines. We have Cypress Vine, balsam pear, and cup and saucer vine, and . . .
Peggy Cornett: Balsam apple. . .
Debbie Donley: Balsam apple is a vine that Jefferson had. It's a very pretty vine, has a small yellow flower and then produces a fruit that's round and bright orangey.
Peggy Cornett: It's warty.
Debbie Donley: Warty. It needs to be a fairly substantial trellis because they get quite large and heavy with all the fruit. But when visitors that are familiar with it and grew up with it, they're just ecstatic to find it here.
Peggy Cornett: It's from Asia. when we get visitors from China, for example, they recognize it immediately. It's called bitter melon.
Michael Tricomi: Bitter melon.
Peggy Cornett: The Balsam Apple makes the reddish fruit, and then the Balsam Pear makes a long, yellow, almost like a big banana.
Debbie Donley: A bumpy cucumber is what I think of.
Peggy Cornett: Yeah.
Michael Tricomi: The seeds are really interesting, too. The pattern on the seed itself.
Debbie Donley: They're brilliant red and gelatinous.
Peggy Cornett: Sticky, yeah.
Debbie Donley: And they're very sweet.
Peggy Cornett: The seed will pop open in your hand when it's ripe, it just explodes. And we used to leave them on the ground because it's hard to get that sticky coating off of it. And the ants will clean it off for you. And then you have perfectly clean seeds.
The genus name is Momordica. And the root of that is “to gnaw.” And if you look at the seeds, it looks like something has been munching around the edges of it. So that's how it got that name. Momordica balsamina is the balsam apple and charantia is the balsam pear.
Debbie Donley: And you can eat them, but you have to pick them when they're green and saute them and they're still quite bitter. I didn't realize you're supposed to eat them sauteed and green. And I tried them when they were nice and plump and lush and orange and it's almost like a persimmon. It just . . .
Peggy Cornett: . . . turns your mouth out inside out . . .
Debbie Donley: won't do that again.
Peggy Cornett: No. Are you going to plant the Caracalla bean this year?
Debbie Donley: It's planted with the cup and saucer vine because last year I just had cup and saucer vine planted there and the guides really missed the scent of the Caracalla wafting up to the terrace, so I put a mixture this year.
Peggy Cornett: That's going to be nice.
Debbie Donley: t'll be a while before they start to bloom. But once they bloom, they will continually bloom.
Peggy Cornett: And the Cypress Vine is a type of Morning Glory. It's an unusual morning glory. It has very ferny-like foliage. And the flowers are like little firecrackers. They're red, star-shaped flowers.
Debbie Donley: And the hummingbirds love them.
Peggy Cornett: They love them so.
Debbie Donley: try to plant that near where Thomas Jefferson speaks so that while the visitors are listening to him, they can also watch the hummingbirds flit by. I also planted Zinnias there for the same reason because the Zinnia elegans, which is a species Zinnia, really attracts the butterflies. And so I thought that would be fun to have butterflies flying around all the visitors.
Michael Tricomi: Peggy and Debbie mentioned the Caracalla Bean. Jefferson proclaimed it to be "The most beautiful bean in the world.” It’s also called Snail Flower because its flowers, which are purplish-blue and white, spiral like a snail shell. As Debbie noted, it smells incredible.
Now let’s move on to some other flowers that are starting to bloom.
Peggy Cornett: There's a lot of annuals that are self-seeding for the summer. The Texas Sage and the Browallia . . .
Debbie Donley: They are all appearing. They're very small right now, but that's coming in. And the Blackeyed Susans are self-sowing, which are not annuals, but they do self-sow as well.
Peggy Cornett: And Marigolds?
Debbie Donley: haven't seen any coming up yet, but they will. Same with the zinnias. So if you just pay attention to what's coming out of the ground and you know your weeds, you can weed the weeds out and leave the flowers in. The whole garden can be self-sown and it can all be annuals. People don't realize that they'll come back every year if you let 'em go to seed. Of course you can't mulch. It's also good to scratch the soil a little bit in the spring, so they have a nice bed to grow in.
Another beautiful flower that really amazed me, Michael, you had planted radishes down in the production garden for the pepper plants, and that bloomed with a beautiful white flower. It was just a whole field of white flowers, and it was radishes as a cover crop, is that correct?
Michael Tricomi: That's right, yes. It actually held up pretty well as a cut flower. I cut some and put them in a vase and they lasted for quite a while. But it's a common cover crop. There are forage radishes and tillage radishes that get very long, they go very deep into the soil, and just create these pockets. so when you till it with the tractor, it just breaks it all up and adds nice organic matter back in.
Michael Tricomi: That brings us to the vegetable garden, where we've been preparing for summer vines as well.
Michael Tricomi: We've been setting up teepees and poles for our climbing beans. They can range from about seven feet to about 10 feet tall. We'll be direct selling all of our beans so that they can climb up and be supported by those structures. We'll start to see a lot of different elevations and changes in height in the garden.
You can smell the strawberries from Mulberry Row. It's a really, really powerful the scent. Jefferson recorded Alpine Chile, the Chilean strawberry, white strawberries, and then scarlet as well. So a few different strawberry varieties were grown.
Peggy Cornett: And the Chile strawberry was part of the parentage of our modern strawberries. And it's native to the Chilean mountains. And it's a larger berry and when it crossed with the smaller alpine strawberries, that's how they started selecting the modern strawberry that we know today.
Michael Tricomi: And they're producing very, very many this year.
Peggy Cornett: They're even in our cafe offerings, I believe now.
Michael Tricomi: Yes, we gave some strawberries to the chef. He used them as a garnish, used them in some salads, so that was really exciting.
Debbie Donley: saw a family down there sampling. They were all huddled together and trying out the strawberries. I'm sure it's a moment they'll remember.
Michael Tricomi: There's so many of them and they take so long to pick that it's nice to be able to stroll through the garden and taste one of the strawberries that are growing there.
Peggy Cornett: It's a good year for strawberries. I have some regular strawberries at home and it's incredible how good they are.
Michael Tricomi: Mine are doing well at home too and I've heard from several others that theirs are. It's just the right conditions, I think. The temperature and the rain.
Weeds and Mulch
Michael Tricomi: This month, we wanted to tackle something that just about every gardener struggles with -- weeds.
Peggy Cornett: They always say a weed is a plant out of place. But the concept of weeds nowadays is very different than it was for Jefferson. And apparently a lot of plants that were considered weeds in his day are really just native plants, like the elderberry and poke. And they can be very rambunctious in the landscape, but they're not invasive plants, or alien plants from another location.
Michael Tricomi: One of the weeds that he mentioned in the Notes on the State of Virginia was Jamestown weed or Jimson weed. He actually listed that under the medicinal category.
Peggy Cornett: It's a famous story about how the early settlers there at Jamestown were eating the seed of the jimson weed, which is hallucinogenic and apparently people came and found people up in the trees because they were hallucinating. It was really probably really scary. And so we got the name Jamestown weed.
Michael Tricomi: The latin name is Datura stramonium. It's native to Central America but has spread northwards as far as New England. It's also called thorn-apple because it has a large green seed capsule covered with spikes. It was traditionally used as a painkiller but all parts of the plants contain dangerous levels of hallucinogens.
Peggy Cornett: But other plants that in Jefferson's Day that we still consider weeds, like dandelion and burdock and thistle were from Europe. They came here with the early settlers who brought crops and some weeds just came in in the ballast that was in the ship that they dump out on the shore when they landed, and it might have a lot of weeds in it.
Debbie Donley: Didn't some of them come as food crops as well, like the garlic mustard, which is everywhere. I know Peggy pulls it all the time when we take walks, she'll just yank it out as she goes.
Peggy Cornett: Yeah. It grows in our forest, which is unfortunate.
Michael Tricomi: He also mentioned clivers or goose grass, Galium spurium, which today we refer to as false cleavers. I was just pulling them out in the garden today. So they're quite abundant.
Peggy Cornett: They're stiill here.
Michael Tricomi: They're still here.
Peggy Cornett: But apparently Jefferson was planting crabgrass in his fields, which now we all hate crabgrass.
Debbie Donley: He also planted poison ivy, didn't he?
Peggy Cornett: He considered it in an ornamental vine.
Debbie Donley: He also listed what we know as Virginia Creeper under ornamental as well. He just called it Ivy.
Peggy Cornett: Virginia Creeper is beautiful. It's just very rambunctious. In the fall it's spectacular.
Peggy Cornett: But there's a lot of vines now that we consider invasive plants because they smother the trees and they strangle them. Bittersweet and chocolate vine. Even wisteria.
Debbie Donley: How about kudzu?
Peggy Cornett: Porcelain vine, kudzu. Those are Asian species. They weren't around in Jefferson's day and they're a real problem in our forests, especially, and on the roadside.
Michael Tricomi: had a lot of English ivy climb up a hemlock tree at my house, and thankfully we found if you cut it at a certain level the rest of the vine die off. But it was strangling that poor hemlock for quite a while.
Peggy Cornett: There was a lot of that here at Monticello a number of years ago. And we were able to, you know, sever the root at the base of the tree. And you just wanna let it die on the tree. You don't want to try to pull it off because it can damage the bark of the tree. It'll fall off eventually.
There are a couple of species that are in our landscape here that Jefferson really liked that are considered quite weedy in other parts of the country, such as the Scotch Broom. But he wanted to have labyrinths of broom at Monticello and they're quite showy, but they don't tend to have a long life here in this part of the country, but on the West coast, in Oregon and Washington, it's a real problem.
Debbie Donley: Some of the plants that we grow people are amazed that we're growing them because where they come from, say, Florida, lantana is considered just terrible and same with the Cypress Vine.
Peggy Cornett: Even the Chinaberry is considered weedy in the south. It's a little bit out of its natural zone here in Virginia. But Jefferson planted that in the grove. He called it the Pride of China, the Chinaberry.
Michael Tricomi: Like Peggy said, a weed is a plant out of place.
So how do you deal with weeds? Jefferson didn't have chemical weedkillers and we try to follow traditional gardening methods, so we don't use a lot of chemicals either.
Pulling Weeds and Mulching
Debbie Donley: Mostly I just hand pull them. If you get the weeds out before it forms seeds, then you're halfway through the battle. One of our wonderful volunteers has an extensive garden and she has just been really adamant about getting her weeds out before they go to seed, and now, after three years, she hardly weeds in her garden at all. She uses mulch. But she's basically eliminated her weeding problem.
Peggy Cornett: And another thing too is to not leave a lot of bare ground. Let the plants grow. If you have a desirable plant, that cover the ground. It really makes a huge difference.
Debbie Donley: Plant them thickly.
Peggy Cornett: Thickly. Yeah.
Michael Tricomi: One of the ways we try to suppress weeds is through the use of cover crops, because then after you till it in, especially wheat and rye, it has a lot of mass to it. It does create sort of a mulch layer as well, and it helps deter other weeds from coming up.
Michael Tricomi: A lot of home gardeners use mulch to suppress weeds. A little bit is fine, but if you lay it down too thickly, you can create problems.
Debbie Donley: People need to understand how to use mulch. You see so much of the time, what's called in the trade, mulch volcanoes, where they'll mulch right up to the trees. And that's a very bad practice because it does allow a place for insects to go. You should have your mulch pulled back, like two inches, three inches from the base of your trees.
Michael Tricomi: t can really retain moisture as well. So that damp environment is usually not good for many reasons.
Debbie Donley: f you see the mulch volcanoes, pull the mulch back and you'll see how the bark has changed under there. And it's decaying and it's not a good, healthy situation.
Peggy Cornett: You do want to pull it away so that you still see that root flare going into the ground. And no more than two inches of mulch and really the best thing on a tree is to mulch all the way out to the drip line if you can.
The other problem with heavy mulch is that it attracts voles. Moles like to tunnel through it and the voles come in and you get a real problem with that, as well, right?
Debbie Donley: use it around the Gardenia and I use it in the rose beds, because it does help prevent black spot because it's soil-borne and the rain, if there's mulch there, it doesn't splash on the leaves. But even that is a very thin layer. But I don't believe, for the most part, Jefferson used mulch, so
Peggy Cornett: We don't have any record of that. Yeah.
Debbie Donley: So I just weed and then I weed some more.
Peggy Cornett: And we don't use it in the vegetable garden either, really?
Michael Tricomi: We've mulched around some of our perennial herbs, just to keep some of the weeds down around them. But again, very lightly. And it also can help to overwinter certain things, like our artichokes, we did add some mulch in there as well, because they can be a tender perennial.
And then, you mentioned roses, it's similar for tomatoes too. You want to make sure that soil doesn't splash up on the leaves. Usually a straw mulch or grass clippings under them. That's typically a good idea.
Debbie Donley: Did you use pine needles at one point around the strawberries?
Michael Tricomi: We did, yes. They like the acidic nature of the needles. So we put Pine needles around our newly planted white strawberries.
Debbie Donley: Which are very sweet.
Michael Tricomi: They're very sweet.
Michael Tricomi: Let’s hear from some recent Monticello visitors.
Paul: Hi, my name's Paul and it's my first time at Monticello and, so far enjoying the trip. Very, emotional.
Peg: My name's Peg. I'm his sister. He's the history buff. He could tell us more about Jefferson than they have on all these plaques, but it's our first time to Monticello. It's beautiful.
Summer Flowering Trees and Shrubs
Michael Tricomi: Now it's time to talk about a few trees and shrubs that flower in the summer. For that, our horticulturist Robert Dowell joined Peggy. They begin with the Goldenrain Tree, which has special significance here at Monticello.
Robert Dowell: The scientific name is Koelreuteria paniculata, and it is the Goldenrain Tree, is how it's known to most folks. It is native to East Asia, Japan, the Koreas, and Northern China. It's generally a small to medium stature tree. Mature height might be somewhere between 30 and 40 feet and about as wide. And it gets the name "Goldenrain" because it has a incredibly showy bloom of yellow flowers in mid-summer in our climate.
Peggy Cornett: It's like a cluster of little flowers.
Robert Dowell: A panicle is a long cluster of flowers, like a giant tassel. And lots of different trees have panicles. And the Golden Rain Tree is one of the showiest ones.
Peggy Cornett: And we're very fond of it because Jefferson received seed of this tree from his friend Madame de Tessé. And there's wonderful history about it because it was first introduced from Asia to the Botanic Garden in Paris. And and so we believe that Madame de Tessé, Jefferson's friend, who's had an incredible estate outside of Paris, sent Jefferson seed and he wrote back to her in 1811 saying that "Since I have the pleasure of writing to you, I have to acknowledge the receipt of the seeds of the Koelreuteria, one of which has germinated and is now growing. I cherish it with particular attention as it daily reminds me of the friendship with which you have honored me."
And this kind of botanical friendship was really carried on by plant exchange, people were writing letters and sending plants and seeds, sometimes across the Atlantic. And sometimes Jefferson would be writing to someone who had already died, but he wouldn't know it for a couple of years. And so that was the case with Madame de Tessé, when later he sent her seeds of the Snowberry that had just been brought back from the West by Lewis and Clark. By the time that the Snowberry reached her, she had already passed away.
But the Goldenrain Tree, it's believed now that Jefferson was probably the first American to cultivate this plant from Asia in our country. The seeds will germinate pretty readily, but it's not airborne. It's a heavy round seed, so it's not invasive, like an Ailanthus tree for example. In some parts of the United States, it is considered invasive. But here it's just a beautiful ornamental. When they flower it's really glorious.
And the other thing that's interesting about the Goldenrain Tree is that most flowering trees flower in the spring. And here we've got one that is very showy in the middle of the summer.
Robert Dowell: Horticulturally, it's a very adaptable tree. It's actually a good street tree because it's very tolerant of a wide range of conditions. It prefers full sun, but it can tolerate part shade. It can take heavy clays to loams, to sandier soils acid to alkaline. So it's very useful in that regard.
And the leaves of the Goldenrain Tree are what's called pinnately compound, which means instead of one leaf, you have a long rachis, which is a long center vein and then along that vein are the individual leaflets. And other native trees that we have, you'll see in the woods come they have this feature like walnuts, hickories.
Peggy Cornett: Ash.
Robert Dowell: Ash, right? Yeah. But the Goldenrain Tree has that feature as well as the large pannicle flowers.
Peggy Cornett: The seed pods are interesting too. They're round seeds that are enclosed by a papery capsule.
Robert Dowell: Yeah. It almost resembles an oriental lantern.
Peggy Cornett: Yeah. Very.
Robert Dowell: Some people describe it like that.
Peggy Cornett: The trees that are still growing at Monticello, we believe are descendants from ones that Jefferson had planted when he sowed that first one germinated in a box outside the greenhouse.
Michael Tricomi: Robert and Peggy also discussed a summer-flowering shrub: Kalmia latifolia or Mountain laurel. It's native all across the eastern United States.
Robert Dowell: It's in the Ericaceae family, which is the Blueberry - Rhododendron family. They're acid loving. When you see these plants in the landscape, you've got acidic soil in a pH range usually five, sometimes below five.
The flowers are very distinctive. They always remind me of cake decorations just the way they look and the way they burst out is very unique and very eye-catching because this time of year, as Peggy was mentioning, most trees and shrubs are done blooming. March and April are really the big months for blooming woody plants in Virginia. So now the forest looks drab green, but the Kalmias and then the Rhododendrons that follow soon after them are real eye-popping. And they can look pinkish purple at first, but then they fade almost to a . . .
Peggy Cornett: . . . to white. They're not as happy here on this mountain because Monticello's soil is not acidic enough. And they grow in the woods near so they're very close.
Robert Dowell: Yeah. Generally, they prefer more gravelly, definitely acidic soils. And so you'll find them in greater abundance in the mountains of Virginia, like towards where I live in Augusta County, it's your classic oak Heath Forest is the term they use for it. Where the overstory is primarily oaks and a few other species like sweet birch or hickory. And the understory is primarily Kalmias, rhododendrons, blueberries, and then even smaller ground cover plants like Gaultheria procumbens.
Peggy Cornett: You have that there?
Robert Dowell: Yeah. A little.
Peggy Cornett: Oh my.
Robert Dowell: Small patches of it.
Peggy Cornett: That's cool.
Michael Tricomi: The common name for Gaultheria procombens is American Wintergreen. It's a native, evergreen ground cover with bright red berries.
Robert mentioned soil acidity. You might remember from chemistry class that acidity is measured on a pH scale from 0 to 14. Everything below 7 is considered to be acidic. In Virginia, acidic oak forests developed naturally from minerals in the soil.
Now for our last segment: Peggy and Robert are going to talk about another flowering tree.
Peggy Cornett: The tree blooming now into the summer is the Catalpa. It's native. It's a North American species that was planted in the grove at Monticello. And there's two types. There's a southern catalpa, which is Catalpa bignonioides, and then the Northern Catalpa, which is Catalpa speciosa. The northern one tends to grow more upright and very tall. And the southern one is more low growing, horizontal to the ground. And that's what we have in the grove. And it has beautiful flowers. They're white and when you look into the throat of the flower, it has some purple spotting. And then later in the season that when they make a seed pod, it looks like a long, tapering, brown. It's called cigar tree.
Robert Dowell: And even in the winter when it's naked of foliage, those seed pods are showy in their own right.
Peggy Cornett: They hang on the tree.
Robert Dowell: Yeah. It's a very distinctive look. And they can achieve quite a large size.
Peggy Cornett: Oh yeah.
Robert Dowell: The one on the north side of the West lawn must have a trunk diameter of six feet.
Peggy Cornett: It's massive. They grow fairly quickly, So that one's probably about a hundred years old, but people think it's 500 years old when they see it because it's so big. And it has a lot of character to it, a lot of gnarling, lumps, and fissures, and so forth. It's a grand tree. It's one of my favorites on the mountain.
Michael Tricomi: That's it for June! Thanks for joining us and we'll see you next month. Happy gardening!