June in the Monticello gardens offers a rich array of plants in bloom from Bachelors Buttons and Canterbury Bells to Chives and Cardoons. This time on “A Rich Spot of Earth” we focus in on another star of June, Amaranths, and discuss how to manage garden pests and diseases. We also take a special look at one of the oldest tree species in existence, the Ginkgo.

Featuring Peggy Cornett, Curator of Plants; Michael Tricomi, Manager and Curator of Historic Gardens; Debbie Donley, Flower Gardener; and Robert Dowell, Senior Nursery Associate at the Thomas Jefferson Center Historic Plants.

Michael Tricomi: It's June at Monticello and there’s a lot to see on the mountaintop: Bachelors Buttons, candytuft, canterbury bells, cardoon, China pinks, and chives. And those are just a few of the purple flowers to enjoy right now. Check out the “In Bloom at Monticello” feature on our website to discover what blooms when.

In today’s podcast, we’re going to focus in on amaranths, garden pests, and the ancient Ginkgo tree.


Michael Tricomi: This is “A Rich Spot of Earth,” a podcast about gardening and the natural world. I’m Michael Tricomi, Manager and Curator of Historic Gardens at Monticello, Thomas Jefferson’s home in Albemarle County, Virginia.


Michael Tricomi: Curator of Plants Peggy Cornett and Flower Gardener Debbie Donley recently sat down to talk about Amaranths.

Peggy Cornett: Amaranth is a big family of annual flowers, mostly tropical flowers and grain crops too. And Jefferson documents several Amaranths. The Globe Amaranth, its genus name is Gomphrena globosa and it has really showy, round, clover-like flowers that are in magenta and pink and white. And it's one of our most popular plants. It's very hardy and tough in the garden.

He also documents the tricolored amaranth or the "Joseph’s coat," which I believe seed was sent back from France in 1786. But they're from South America. I guess you can say they don't really have a showy flower because you're really looking at the colorful bracts of the leaves. They're orange, yellow, red—a mixture of the coat of many colors. That's where it gets its name, but it starts out green and dark burgundy.

Debbie Donley: It evolves into that.

Peggy Cornett: It changes as it gets bigger. Yeah. And it can get five feet tall.

Debbie Donley: I like to stake them. If you get a big storm, you come to the garden and they're laying sideways and then it's really hard to fix them. So I stake them early and that way they're protected and they stay upright.

Peggy Cornett: And you can't really pinch the Joseph's coat.

Debbie Donley: I don't. they don't really branch out like a lot of things do.

Peggy Cornett: Some things you just don't want to pinch them.

Debbie Donley: Right.

Peggy Cornett: And then we also think the "Princess Feather" was probably a love-lies-bleeding, which is another amaranth—that's Amaranthus caudatus. So there are several types of amaranths in the garden and they really carry us through the summer months. They're very showy. They love the heat.

Debbie Donley: The love-lies-bleeding is very unusual. It gets quite tall, maybe about five feet if it's happy. And it has what, to me, look like pink dreadlocks. The flower itself it's on a long stem and its individual little flowers that make up the whole look of the "dreadlock," as I call it. To get the seed off of it, we would pretend like we were milking a cow and hold the box underneath and the seed would all fall down.

Peggy Cornett: The seed is beige, isn't it?

Debbie Donley: Pinkish, beigeish. It's a very pretty seed. And I believe you can eat the leaves when they're young.

Peggy Cornett: Joseph's Coat also.

Debbie Donley: Joseph's Coat as well.

Peggy Cornett: You can eat it like a salad green.

Debbie Donley: You can also use the seed of the Joseph's Coat to grind for flour.

Peggy Cornett: And the seed is very black. There's a cereal called Amaranth Cereal that's very high in protein and is a very nutritious grain in South America.

Harlequin Bug

Michael Tricomi: Now, we're going to get into pests. Throughout the podcast, you’ll hear us describing different techniques for Integrated Pest Management or IPM. This is an environmentally sensitive approach to dealing with pests, based on an understanding of the pest’s life cycle and how it interacts with the environment.

Let’s start with some general pointers: First, keep your plants healthy and consider selecting disease- and pest-resistant cultivars. Second, knowing when to look for pests and timing treatments is a big part of IPM. Third, we try to use a variety of treatments—chemical, mechanical, and biological. That’s important because you don’t want the pests to build resistance to a particular treatment. Fourth, maintain good sanitation—that includes pruners and tools but also being aware of garden debris, where pests often over-winter. Peggy and Debbie talked about the Harlequin bug, which is in the stink bug family. They’re black with bright red, yellow, or orange markings.

Debbie Donley: The harlequin bug really enjoys the leaves of the love-lies-bleeding, and it will turn it actually into almost looking like lace, which is pretty cool-looking in its own right, but not exactly what you want. So to avoid that you may just plant it a little bit later because the lifecycle of the Harlequin bug is over earlier in the season. So if you plant them later, then they're not affected.

Peggy Cornett: You start them in the middle of the summer or something.

Debbie Donley: I would say July.

Peggy Cornett: It is a pest that has come about in more recent years, probably in the last 10 years, because we used to not have that problem.

Debbie Donley: There's a lot. And I believe they're in the vegetable garden as well.

Peggy Cornett: Is there an organic method you could use to control them?

Debbie Donley: We do squish them. Sometimes they just reproduce so fast that I just let them be. And people understand, hopefully, that yes, this is a real garden and there’s real insects in there.

Michael Tricomi: The Harlequin bug supposedly doesn't like strong smells. And so any mint or garlic that's planted near it could help deter that.

Peggy Cornett: Is it the harlequin bug that also gets on the horseradish?

Michael Tricomi: Yes. I think they like that sort of shiny, almost rubbery texture, that sort of brassica texture, because we'll see them all the time on our horseradish as well as the sea kale. And then we'll see it on the regular kale as well.

Peggy Cornett: And sometimes the best thing to do with the horseradish or the sea kale is just cut the leaves off and let it resprout. And remove the leaves, you know, that's another part of integrated pest management is keeping your area clean because insects will overwinter.

Cabbage Looper

Michael Tricomi: Peggy and I talked about another pest attacking some of our early summer vegetables.  

Michael Tricomi: In the vegetable garden right now we are harvesting some of our brassica crops. So we have our kale, our broccoli, our cabbage are all ready to be harvested, so we're pulling them out. We are also noticing a lot of pest activity in regards to those crops as well, namely the cabbage moth or the cabbage looper is a really common pest for anything in the Brassica family. And these date back to the middle of the 19th century when they first arrived, but they were pretty devastating in England and in Europe before then.

A lot with pests and insects and disease too is the timing. And so if you can get it at the right time, you can minimize the effect or even sometimes totally do away with it. But when you see those moths flying around, you want to look for the eggs that they’re laying--clusters of little yellow egg mass. You're going to see a little bit of chewing and some holes.

Peggy Cornett: That's when to check it, really. That's what I always do. I see a hole and I just flip the leaf over and find it.

Michael Tricomi: You check under the leaves. Check around the whole plant. And if you can squish the eggs, that'll help save you in the long run. Once the eggs hatch, the little worms will emerge and they'll just chew holes in all of the leaves that they can find. In Williamsburg they use cheese cloth. They'll just cover the plant just to prevent the moth from laying the eggs.

Peggy Cornett: It looks like a mesh or cheesecloth, basically.

Michael Tricomi: It's important to be diligent and to check them regularly. Monitoring, that's one of the first steps of integrated pest management. And you really want to catch them before the head starts to form, because then they go further into the plant and they hide among the leaves of the head. And they can be really hard to find.

Peggy Cornett: And they, well, is it called frass? They leave this kind of green …

Michael Tricomi: They'll leave their droppings behind—the frass—yeah. So if you see that on your plants, near some little holes. That's what's causing it. And as they chew through those brassicas, they'll get pretty big. And so, if it's manageable in your garden, you can hand-pull them off your plant. A common method is to put them in a bucket of soapy water. You could make an elixir or a tea out of tansy leaves too. And that is supposed to help deter this cabbage looper.

Peggy Cornett: Oh, and can you spray it?

Michael Tricomi: Yeah, you could spray it on the plant.

Visitor Spotlight

Michael Tricomi: Now let's hear from some recent Monticello visitors.

Dutch visitor:

 I'm Sweta. I'm from the Netherlands. I came here with my family and my wife was especially interested in this place and that's why she bought the tickets for us. It's amazing, especially the people doing the tours telling about the history and actually making you relive it.  That's amazing that we have people like that to keep the story going.


Michael Tricomi: There are a lot of pests and diseases affecting our trees as well. One big concern in our region is cedar-apple rust. Horticulturist Robert Dowell joined us to talk about it.

Robert Dowell: The cedar apple rust is an interesting disease because it has two hosts. It has the Eastern red cedar and the apple tree. And there's other variations of it. There's Hawthorne cedar rust. For some reason, the Rosaceous family of woodies just has a lot of rusts.

Michael Tricomi: Diseases affect trees in different ways. Vascular diseases are more serious because they attack the trunk and branches. Foliar diseases attack the leaves. Rust is a foliar disease that causes rusty brown and black spots on the plant's leaves.

Robert Dowell: And eventually the leaves will be totally covered in these rust spots and they'll often fall off. And it affects the plant's ability to photosynthesize, so it can't effectively make food for itself. And it'll affect the fruit too. You'll see apples that are rust-covered.

Peggy Cornett: They'e not pretty.

Robert Dowell: They're not pretty and they're mutated. They're not appetizing at all. And so it can totally defoliate the plant. Foliar diseases can be serious, but they're generally easier to manage. Cedar-apple rust, it generally won't kill the plant. But if you leave it untreated, it'll weaken the plant and over time you'll lose vigor, you'll lose your fruit crop, and the tree might eventually succumb to it.

A lot of people think they can just cut down all the cedars near their apples and hope that they don't get cedar rusts. But the fact is, in Virginia, there's an eastern red cedar on every street corner.

Peggy Cornett: There are two in my yard.

Robert Dowell: Yeah, there could be one half a mile away and that could be a source of infection.

Even though it's a disease that requires two hosts, the best treatment options are to focus on your apple tree. So what we do for treatment is timely sprays. During the spring, as those leaves are emerging, they're most vulnerable to receiving the spores from the cedar host that wash on them during spring rains. So timing your sprays to prevent that is the best treatment option. And it's usually not just one application, you’ll usually spray and then wait a few weeks and then spray again. And the thing with fungicides, most fungicides, is they're actually preventative. So you're not spraying the fungicide to heal the infected leaves, you are spraying the new foliage to protect it from future infection. So once you've got infected leaves, they're done. They're going to fall off eventually. You're trying to keep the new growth from developing that disease. So that's why you have to time it with the flush of the plant. And you don't have to do it the whole growing season. You really only have to do it for a few weeks or a month in the spring when that disease is active in its infection phase of the apple tree.

Figs actually get a rust too. It's not like the cedar-apple rust where it has that alternate host. It's on the figs. But for that, I will sometimes dust sulfur. So just elemental sulfur, the yellow, chalky sulfur that you can crush up and put in a special applicator device. And it's very safe and very effective.

Peggy Cornett: Isn't it good for roses too?

Robert Dowell: So I've used sulfur on figs, on apples, on roses. It's a good broad-spectrum fungicide. And it's relatively safe too. It's a natural element. It's not a synthetic material.

Michael Tricomi: Another key to pest and disease control is keeping your plants healthy.

Robert Dowell: When you're thinking about pests and diseases, you want to optimize the water, the fertilizer. You want to make the plant as healthy as possible otherwise, so that it can push itself out of whatever disease or pest it's dealing with. Sometimes just giving plants an extra boost of fertilizer can really go a long way in helping them combat a disease.

Peggy Cornett: That just brings up what Jefferson wrote to his daughter, Martha, when her vegetables were doing poorly. And he said, well, it's due to the "leanness” of your soil, and in the coming year we're going to apply a serious amount of manure to the garden so that your plants can "bid defiance to insects and diseases.”

Michael Tricomi: There is truth to that. Healthy plants are more resistant to these pest pressures that we have.

Peggy Cornett: Absolutely. That's great wisdom.


Michael Tricomi: Another type of pest we wanted to mention are boarers. They boar into the plant's main stem or trunk. We struggle with them in the fruit orchard and the vegetable garden.

Robert Dowell: As far as tree pests go, boarers are the most serious because whereas a caterpillar might just munch on leaves, the boarer will kill entire branches or the entire tree, like emerald ash boarer, bronze birch boarer, peach tree boarers.

Peggy Cornett: Because they're cutting the xylem flow.

Robert Dowell: Yeah. The circulation of the tree is being severed by the boarers feeding.

Peggy Cornett: I think there were boarers in Jefferson's day. They talked about picking them out by hand. You just dig it out with a stick or something.

Michael Tricomi: Same goes for the squash vine boarer, too. If you have a large population of that, they'll just decimate the entire squash crop because they kill that main stem.

Peggy Cornett: It seems like it happens overnight too. And that's another one that if you're paying attention and monitoring it, you can actually get rid of it.

Michael Tricomi: Yeah. They say you could just take a little needle. And just find the hole that it's burrowed into and just spear it and you can kill the boarer before it burrows itself further into the vine. And then if you've got a squash that likes to spread, in between the leaf nodes, you can encourage it to set roots out there.

Peggy Cornett: That's actually a very good method, when it's sprawling because you can get it to re-root further on. And so the main part of the plant, maybe it has died, but you've got another plant that's rooted on and they'll root really quickly.


Michael Tricomi: That’s enough about pests! Finally this month, we wanted to talk about a spectacular tree: the Ginkgo.

Peggy Cornett: Jefferson first obtained Ginkgos from his friend William Hamilton, who was actually credited with introducing them to America. And it's a mixed bag because he did introduce the Ailanthus to North America as well, which is one of our biggest pest trees. But the Ginkgo was quite a wonderful addition. It's a very interesting tree.

Robert Dowell: They call it a living fossil.

Peggy Cornett: A living fossil, yeah.

Robert Dowell: It's literally one of the oldest trees in existence. It's a monotypic genus, which in botanical terms means it's the only species of its kind in that particular taxonomic group. And I think some scientists believe the ginkgo is 200 million years old, possibly. So it predates many other plant species.

Peggy Cornett: It's from China, of course. It went back to the Jurassic period apparently. So it was, thought, it was thought to be extinct at one point too. It's really a relic. And it was preserved in Chinese monasteries.

Robert Dowell: Very sacred in a lot of East Asian cultures. There are centuries old Ginkgo specimens in Japanese, Korean, and Chinese temples. And then the Europeans became familiar with it, I think, in the 17th century. Then from there, Jefferson probably got involved with it.

Peggy Cornett: And apparently the first trees cultivated in Europe turned out to be all male trees. The female tree is the one that has the odoriferous fruit. But when Hamilton gave Jefferson a Ginkgo, he said it had a good, eatable nut.

Robert Dowell: Yeah, the nut is valued in Chinese medicine as a supplement.

But it's a beautiful tree. A mature ginkgo specimen is really a site to behold. They can become massive. We have one at CHP that's, I want to say, 50, 60 feet tall.

Peggy Cornett: That’s a big tree. Yeah. And it's a female.

Robert Dowell: Unfortunately, the females produce that, well, we call it a fruit, but botanically it's not a fruit, but we'll call it a fruit just for simplicity. And it produces a very foul odor when it decomposes in the autumn. Some people call it like rancid butter.

Peggy Cornett: Well, that's nice . . .

Robert Dowell: That's one of the nicer descriptions for it. But in the landscape, horticulturally, if you're going to grow a ginkgo, generally you want a male ginkgo.

Peggy Cornett: But you won't know that until it's about 15 years old.

Robert Dowell: Exactly. If you were to grow a ginkgo from a seed, you're going to be waiting a decade or more before you find that out. So if you ever purchase a ginkgo in the nursery trade, make sure it's a male cultivar clone.

Peggy Cornett: In the fall, the whole tree turns golden all at once, and then

Robert Dowell: They are famous for their color.

Peggy Cornett: It's fabulous. And there's a real famous one, the Pratt Ginkgo it's called, at the University of Virginia, which was planted in the 1850s, I believe. And it was named after the garden superintendent at UVA.

Robert Dowell: The ginkgo leaf, you wouldn't mistake it for any other tree leaf.

Peggy Cornett: Chinese maidenhair tree is another name for it and it looks like a maidenhair fern.

Robert Dowell: Right. It has a very distinctive fan shaped leaf that I can't think of any other tree that has that shaped leaf. And often there's a notch in the center. So the scientific name ginkgo biloba means two lobes. So that's a reference to the leaf shape.

They're relatively slow growing, as far as trees grow. They can grow fast under optimal conditions. But, generally, slow to moderate growth habit or growth rate is what most horticulturalists would describe it as.

Peggy Cornett: And they've developed some that are fastigit. They just grow like a column. They're just going straight up. And they're planting them as a street tree because they're very resistant to pollution.

Robert Dowell: And very pest resistant—there’s almost no diseases that really can knock down a ginkgo. And there's dwarf cultivars too. There are variegated cultivars. There's a whole slew of cultivars there for ginkgo.


Michael Tricomi: That’s it for June. Thanks for listening and please join us in July when we’ll talk about beneficial critters in the garden. Until then, Happy Gardening!