Prologue

Michael Tricomi: It's July at Monticello and it’s been exceptionally hot and dry this year. We’ve got some gorgeous flowers in bloom—marigolds, blackberry lilies, globe amaranth, and hibiscus—but keeping things watered is a never-ending task.

In today’s podcast, we’re going to talk about drought, along with beneficial insects, and Jefferson’s dream of growing olives in Virginia.

Introduction

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.

Drought and Watering

Michael Tricomi: Curator of Plants Peggy Cornett, Flower Gardener Debbie Donley, and Horticulturist Robert Dowell discussed how we’re dealing with the hot, dry weather right now.

Debbie Donley: It's been a long dry period without rain. It's been nearly five weeks and we've only had about six one hundredths of an inch of rain. And so the ground is crispy. Everything is just brittle. We have an irrigation system in place, but there's been issues with that, with the pump. Guests are becoming a little shocked.

Peggy Cornett: Part of the problem too is the excessive heat. We've been in the nineties.

Debbie Donley: Plus . . .

Peggy Cornett: Yeah, with the heat index over a hundred. This is early. So, it's been a pretty difficult year so far. 

And Jefferson had similar issues. There were years at Monticello when there was really excessive drought and then followed by heavy rain, a year of rain. So, in his famous quote, he said, "If Heaven had given me my choice of a position and calling it should have been on a rich spot of earth, watered and near a good market for the production of the garden." So being well watered is very important, especially for a vegetable garden.

Looking back at the records, Charlottesville had the wettest year on record in 2003, and that year we had over 74 inches of rain. But prior to that, we were at the end of a three- or four-year drought. And it was quite difficult for all of us to manage that because once the wells go dry, we do bring water in from the city, but we also have a spring, and that stopped producing water. The wells at Tufton farm, the nursery at the Center for Historic Plants, went dry.

Debbie Donley: And it was shocking the state of the garden, but we were just trying to keep it alive. It was really survival in the garden.

Peggy Cornett: It can be really tough to see plants just suffering so much when you can't really do much about it.

So water is an ongoing issue, and I think it will continue because, as we've talked about, climate change, the weather getting warmer, drier, and unpredictable. We have storm bombs and then we have long periods of heat dome.

A good thing about dry weather is seed saving. In 2003, when we had so much rain, we had a really hard time saving enough of our seed because it was molding, it wasn't ripening in the field well, and we couldn't get places to dry it properly. And so there was a big loss of our seed production. So, that's the other end of too much rain.

Debbie Donley: Right. And I don't know if this has anything to do with the weather, but it's really been a good year for lack of Japanese beetles, of course, their larvae are in the ground, which is rock hard and dry. And I don't know if that's affected them or not.

Peggy Cornett: That's interesting.

Debbie Donley: We had the summer campers here and one of the activities is usually to pick Japanese beetles off the plants, and they usually get lots and lots, and they came up with two or three.

Peggy Cornett: Isn't that funny?

Debbie Donley: Even on the roses, which the beetles love. Have you seen many over at CHP?

Robert Dowell: Not nearly as much in a typical year. And also, on that note, the drier weather is better for foliar diseases on plants. We're seeing a lot less of that. Among the roses, like black spot in a typical year is something we have to contend with more. But this year we've had minimal black spot damage, so that's less spraying we have to do. I guess we're spending time watering maybe instead of spraying.

Peggy Cornett: The vineyards are great. They're all happy about this dry weather. It's perfect for grapes and reduces disease and grapes get a better flavor when they're a bit stressed. They put more sugars into the grape itself. So we'll have a good year, I think.

Drought Tolerant Plants

Michael Tricomi: As water becomes a growing concern, people are seeking out drought tolerant plants. Here are a few we grow at Monticello.

Peggy Cornett: There are certain plants that do pretty well in dry weather and one we were thinking about is the Gaillardia, the Blanket Flower. And it was found by Lewis and Clark. They came across this plant in 1806 in July on the dry hills of the Rocky Mountain, which I really love. And so, it does well in dry weather. It keeps blooming all through the summer.

Debbie Donley: The insects love it. It self-sows, even though it's a perennial.

Peggy Cornett: It's an aster, so it's got a central disc and then these ray petals that are yellow and orange colored.

Debbie Donley: They also make a great cut flower. At first, they wilt, but then they come back after they've had a good drink.

Peggy Cornett: A lot of pollinators like them. And so, it's really a great plant in the garden. That was another plant you were talking about that sprawls. It gets about two or three feet, right? So it's maybe good to trim it back. It'll cascade over where you want it to grow.

Debbie Donley: Right, like the sidewalk. So plant it further back knowing that it's probably going to flop over.

One thing to remember though about planting plants that resist drought, they need to be established first. They need water in the beginning periodically. They do need to get established first before they can take it.

Peggy Cornett: And then another one is the Snow-on-the-Mountain, which is another Lewis and Clark plant. And that's a Euphorbia, Euphorbia marginata. And they discovered this again in July. Apparently, Captain William Clark collected seed of this plant along the Yellowstone River in Montana, but its natural distribution is a wide area along the Missouri River in North Dakota. And it's very adaptable to all kinds of soils. And it’s a Euphorbia and it has a white sap in it, and it's resistant to deer. And so that's a good thing about it too.

And it gets more beautiful as the season goes on. It's not really a flower. It's like a poinsettia where you're looking at the bracts below these kind of small flowers and they're pure white as the season goes on.

Debbie Donley: They even get big enough that I've heard of people making a hedge out of them.

Peggy Cornett: They could, yeah. They could get three or four feet tall.

Debbie Donley: And the combination of the Gaillardia and the Snow-on-the-Mountain is really pleasing.

Peggy Cornett: Yeah. We have a Lewis and Clark corner in the garden on the flower walk and these are the two hits of the summer, really, through the whole summer.

Peggy Cornett: And then there's another plant we grow at the Center for Historic Plants. It's called Pycnanthemum muticum, and it is native. It's apparently native in moist woods from Massachusetts to Michigan and south to Louisiana and Florida, so it has a broad range. They say it's native to moist woods and meadows, but we have a bed of it that's never been irrigated and it doesn't seem to faze it, really, in the heat and everything. It's one of my favorites and it's very aromatic.

Debbie Donley: It's great in flower arrangements as well.

Peggy Cornett: How would you describe the fragrance?

Robert Dowell: Similar to spearmint but maybe not as pungent. And it does spread but not nearly as aggressively as a spearmint would. So it's easier to contain in a garden space.

Peggy Cornett: I cut mine back early in my own garden, because it gets three feet tall or more. So it's just starting to flower now. They're not as showy, but they're pretty. There's these tiny little flowers with this kind of white, leafy bract. And the pollinators are all over it—the bees.

In Charlottesville, there's a lot of efforts to plant what they're calling "Piedmont prairie gardens" in strip by the sidewalk and the street. And it's really tough and it can grow there quite well without any care or watering or anything.

Watering Vegetables

Michael Tricomi: Next, we talked about watering strategies in the vegetable garden.

Michael Tricomi: When we're experiencing drought or a lot less water, you'll see the leaves curl. That's a common sign. Corn, tomatoes will do that. A lot of plants, their leaves kind of curl, but it's really noticeable in the corn.

Peggy Cornett: And also excess of heat. That's a problem for tomatoes. They won't form as easily on the plant when it's really too hot, I think. Is that right?

Michael Tricomi: Yeah. A lot of these peppers, tomatoes, eggplant, they thrive in hotter weather. But it's that in combination with drought and inconsistent watering that really does them in. So, really deep watering and then lack of water. And also shallow watering, too. So, if you just get into the surface level and not allowing the water to soak in really well.

One of the big things that we start to see, and it's really common in the home garden as well, is blossom end rot, where the end of the fruit will start to rot and turn brown and make it not able to be eaten. But you'll see it commonly in bigger peppers and larger tomatoes, like slicing tomatoes. Watering--it should be infrequent but deep.

Peggy Cornett: Yeah. My mother used to say give it a good drink of water and then give it a break and wait in between.

Michael Tricomi: And with watering too--timing. A lot of times irrigating during the day is not a good idea. It could dry up too fast.

Peggy Cornett: It's better to water in the morning, right?

Michael Tricomi: Right. And that's what allows the plant to soak up that water and have enough for the hot, dry part of the day. Because irrigating at night could allow for some of those fungal issues to develop, so morning watering is preferred.

Visitor Spotlight

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

Manny: I'm Manny, I'm from Guam. Monticello, it's amazing--just how large it is, the home, around the home, the history, the exhibits, the information, the tours, the garden, the views, pretty much everything. It's great.

Beneficial Insects 

Michael Tricomi: Last month we talked about pests that cause problems in the garden. So this month, we wanted to highlight a few insects that can actually be helpful. We see a lot happening on our artichoke square, artichoke and cardoon. We have the horseradish right there, and that commonly gets the Harlequin Bug. We just started to see them attacking that plant right now. But the artichokes and the cardoons they get just totally full of Lady Beetles.

Peggy Cornett: That's good, right?

Michael Tricomi: That's great. Yeah. We'll see them as well as the assassin bug, wheel bug or assassin bug. They're really commonly found in that square.

Peggy Cornett: What do they attack?

Michael Tricomi: They attack quite a bit, quite a bit of pests. So the wheel bugs, including the assassin bug, they'll eat aphids, moths, butterflies, unfortunately, sawflies, and beetles. So, quite a range.

Peggy Cornett: That's good. We need to get those up on the roses because we get sawfly on the roses.

Michael Tricomi: And I won't go into the method of how they attack them. It’s pretty brutal. But, yes, they're a great thing to see. They look similar to a stink bug or a squash bug, maybe. But they're a little longer. Their shape is slightly different. So don't mistake the assassin or wheel bug for the squash bug.

Michael Tricomi: You can also combine certain plants in your garden to attract beneficial insects.

Peggy Cornett: My mother used to plant marigolds everywhere.

Michael Tricomi: That's the really common one is marigolds, with tomatoes especially. I think it's supposed to deter the . . .

Peggy Cornett: Nematode . . .

Michael Tricomi: Right. Yeah. As well as some of the insect pests too.

We don't plant too many flowers in the vegetable garden, but Nasturtiums for sure. We know Jefferson used the seeds, the immature seeds, as a caper substitute. So we'll have Nasturtiums in the vegetable garden. We'll plant a lot of herbs as well. Borage is really good at attracting beneficial insects. We have Tansey that draws a lot of insects in, the Wormwood when it's flowering. Basil and tomatoes, that's another really good combination. Dill and fennel.

Peggy Cornett: They're attracting good insects. Beneficial insects. We love seeing the butterflies and we love seeing the bees and the hummingbird moths are really cool.

Robert Dowell: Seeing spiders is usually good. Little jumping spiders I see every year in our greenhouse and they're always, for some reason, on peppers and tomatoes. But spiders almost always are beneficial because they're predatory arachnids.

Michael Tricomi: One of my favorite insects are the praying mantis. They're just fascinating to watch. But they'll keep a lot of those insect pests away as well.

Peggy Cornett: There's a wasp that preys on the tobacco hornworm. And that worm attacks the Flowering Tobacco in the flower garden. And tomatoes too, doesn’t it get on the tomatoes?

Michael Tricomi: Tomatoes as well.

Peggy Cornett: It lays eggs on the worm and it looks like it has these white egg cases growing out of its spine, like a dinosaur-looking thing. And those are parasitizing the actual worm. 

Michael Tricomi: They'll hatch . . .

Peggy Cornett: . . . and they go inside the worm and eat the worm. It's a bug-on-bug world.

Robert Dowell: Yeah. If you see if you see that, leave it, because that's a population of beneficials right in front of your eyes.

Peggy Cornett: You don't want to kill it.

Michael Tricomi: Another beneficial insect that we've actually introduced to the garden this year is a really tiny parasitic wasp that goes after the Mexican bean beetle because year after year we always have issues with Mexican bean beetles totally devouring our beans. They'll just leave this skeleton of a leaf behind and they multiply like crazy.

Peggy Cornett: So you're letting them loose into the environment?

Michael Tricomi: Yes, It's called Pediobius foveolatus. It's this really tiny parasitic wasp. We order two little baggies of 40 mummies each, they call them mummies, the egg cases, and they hatch and it'll go after the eggs that are laid by the beetles as well as the larvae itself.

Peggy Cornett: That's fabulous. And it's working?

Michael Tricomi: Well, fingers crossed. We've seen some eggs and we've seen the little wasps flying around. So, yeah, we'll see how it goes.

Peggy Cornett: Well, these parasitic wasps are a real boon to greenhouses.

Robert Dowell: Yeah. We have a beneficial insect program every year where we try and build up a population throughout the growing season. And we'll use parasitic wasps, we'll use predatory mites. And they just arrive in what looked like giant spice shaker bottles. And so you pop the cap off, and they're mixed in with a vermiculite packing medium, and you just sprinkle them on the plants like it was oregano on a pizza. And sometimes you can actually see them hatching and moving around.

Peggy Cornett: They’re very tiny.

Robert Dowell: They're very tiny. And in that bottle you're applying probably a hundred thousand or more of them, and not all of them will live, but hopefully enough will live that a population can sustain itself eating the bad bugs in the greenhouse. It's a big industry. There's laboratories that specialize in rearing these insects and distributing them to greenhouses.

Peggy Cornett: Going back years ago, I was letting these Encarsia wasps out for mealy bug in the greenhouse, and it really did do the job.

Robert Dowell: Yeah. They're very effective. The key to remember is unlike, say, spraying where you get instant results from your application, beneficials, you have to wait a while for the population to build.

Peggy Cornett: And then of course when they take care of the insects, then their population goes down. It's a cycle.

Robert Dowell: We'll start applications, maybe, around April or May. And by that point we have a lot of crops in the greenhouse, and we might be starting to see some pest issues. So if we applied them, like, in January, there'd be nothing for them to eat and it would be a wasted effort. So you actually need a little bit of the bad bugs there as a food source to get them going.

There's no safety concerns when you're applying these bugs. They're totally harmless to people and, a lot of times, they're very specific in who they go after. You have specialized insects and generalist predators. The generalists are things like praying mantis, ladybugs that'll eat anything. And then usually the parasitoid types will go after a very specific species.

Peggy Cornett: Yes.

Robert Dowell: And a general rule, I've learned if you see a fuzzy, colorful caterpillar, do not touch it. It seems like every year we discover a new stinging one.

Peggy Cornett: Oh, man.

Robert Dowell: There are caterpillars out there with bristly hairs that'll sting you as bad as any wasp or bee. So just avoid them if you see them and just hope that maybe a parasitoid will find them.

I've noticed in my work anything in the Rose family or the Dogwood family seems to really attract these insects. So, if you're doing work in those plants, starting midsummer to late summer, just be very careful.

Olive Trees

Michael Tricomi: Finally, Peggy and Robert talked about Olive trees.

Peggy Cornett: It was Jefferson's hope that he could grow olives here at Monticello after he saw them in 1787, when he was traveling into Italy. And he once wrote that, "Olive oil was surely the richest gift of heaven." I think he imported four gallons a year.

And he tried for at least three decades to encourage olive culture in America among southern states. He was able to grow olives once and actually press some oil, but it was a little too cold to really be successful. He had great hopes for the sesame, but I think he would've really preferred to have an olive grove at Monticello because that was his favorite oil.

But now our zones have already changed. I think we're closer to zone eight now than we were before. And we might be able to grow certain types of olives here at Monticello if we have them in a protected location.

Robert Dowell: The olive is such an amazing tree: very drought resistant, very pruning resistant. You can basically stump it within an inch of its life and it will sprout right back up. Fire resistant. Obviously it's been known to cultures in the Mediterranean, in the Middle East, for thousands of years.

I was on a vacation the last few weeks. And I was actually in Greece and a few other countries around it. And I got to see a 2,400 year old olive tree in Montenegro. And it was just as hot over there as it was here, and very dry. But all the olives looked fine because they can take it.

And I think growing olives in Virginia sounds crazy now, but maybe with climate change it won't be such a crazy idea in the future.

Peggy Cornett: I think it's really worth a try.

Robert Dowell: And we can grow figs and pomegranates in Virginia quite successfully, and the olive has more or less the same hardiness and tolerances as those plants in many ways. So it's definitely worth trying.

Michael Tricomi: Yeah. Monticello's always been an experimental site, And so with this warmer climate yeah, we'd definitely be interested to see if we could grow olives here.

Conclusion

Michael Tricomi: That's it for July. Thanks for listening and please join us in August when we’ll talk about planting schemes and peaches. Until then, happy gardening!