Gardening Unplugged - Fragrant Plants

Gardening Unplugged - Fragrant Plants

with Dr. Patrick McMillan

By Published September 2022

In this episode of Gardening Unplugged, recorded on July 23rd, 2022, our Horticultural Manager, Dr. Patrick McMillan, lets you smell everything but the roses. Featured scents: Papa Johns pizza crust, Lysol, Ginseng, and a whiff of lavender. Gardening Unplugged are free classes presented by JLBG/PDN staff during the Garden and Nursery Open House days. These are 15 - 30 minute discussions walking through the gardens, focusing on seasonally prominent topics, plants and garden design ideas.

Plants featured in this video:

  • Berlandiera
  • Hemerocallis
  • Sphinx moths
  • Calycanthus
  • Trillium cuneatum (Little Sweet Betsy)
  • Aroids
  • Monarda punctata (Bee Balm, Dotted Horse Mint)
  • Poliomintha
  • Nicotiana
  • Lepechinia hastata
  • Zingiber mioga
  • Aralia cordata 'Sun King' (Sun King Spikenard)
  • Aralia racemosa
  • Cucurbita foetidissima
  • Cestrum parqui
  • Iris foetidissima
  • Salvia darcyi


Video Transcription

Why are Flowers Fragrant?

This morning, this berlandiera smelled just like chocolate tootsie rolls. Right, it's a super cool plant from Texas that actually... maybe you can kind of smell the tootsie roll fragrance left in it but like most plants’ flowers are fragrant for a short period of time, right. And when we're designing gardens, I love to design gardens for all the senses including taste. Like, I really like to interact with my own spaces and so I love to design gardens that are fragrant in multiple ways. And since we're in the middle of the day and it's 106, you know, air temperature or it feels like 106 degrees today. The plants are feeling the same thing so normally fragrant flowers today aren't all that fragrant, but flowers and the vegetative parts of plants are fragrant for different reasons, completely different reasons, which I find really interesting too.

Dr. McMillan: So why are flowers fragrant?

Attendee: To attract bees?

Dr. McMillan: To track pollinators, yes, pollinators. But no flower is fragrant to attract bees. Bees use their visual acuity to find flowers and so flowers that attract bees have infrared and ultraviolet sort of arrows that point towards where the good pollen or the good nectar is on that flower, and they don't have to be fragrant at all. They may have nectar that smells really sweet like honey that the bees are after but they're not, they don't have to be fragrant to attract bees. And anything that's fragrant, and it's really wild. When you get to be good at plant ecology, like you know it's like psychology for humans. You become a plant psychologist. You can look at a syndrome in a plant and I can tell you about any plant out here.

That white flower over there, right, that hemerocallis. I know that those fresh flowers come out when it gets dark. They don't come out in the middle of the daytime, they come out when it gets dark, and I know that those flowers emit a fragrance because the type of flowers that are white and tubular always smell sweet. They always do. This big lily over here emits beautiful fragrance at night - white tubular flower. White tubular flowers that smell really, really sweet are pollinated by moths. Most of the time by sphinx moths, the fluttering kind. They're the hovering kind of moth, okay. Plants that smell like fruit a lot of times can attract flies. So, things like calycanthus, Little Sweet Betsy trillium.

A lot of plants, and we'll look at a few like this, smell like either poop or rotten meat. A huge number of flowers smell like that. Not just a couple, a huge number. And we love to collect those flowers here in our garden at Plant Delights just so Tony can giggle at people when they walk down the trail holding their nose in the spring, right. A lot of these plants are ancient lineages. They're members of the of the aroid family or they're members of what we call basal angiosperms that really came to be on the planet long before there were bees, butterflies, or moths. And so, they're attracting the types of pollinators that they that were around to attract back then. That sort of Triassic/ Jurassic boundary, right. So, they're attracting flies and beetles instead of hymenopterans, right. So that's kind of just a sampling of what's out there for plant sense with flowers. But most of what we're going to talk about today is not related to the flowers at all. And then you can hold this. And I picked one really smelly so you can hold it at a distance due to Covid, right. You don't have to get close to it. Squish it a little bit and you'll have no problem smelling this plant and it should smell really, really familiar.

Dr. McMillan: What does that smell like to you?

Attendee: Oregano?

Dr. McMillan: Oregano! But it's like way more potent than oregano. What that plant it has in it that you're smelling is a chemical called thymol which is thyme. All of these names for chemicals are pretty much like, you take thyme oil and if you're going to make a chemical name out of it it's an oil so it's an ol so it's thyme-ol, right? And so, it is. It's thyme oil that you're smelling in there. It's what gives oregano its flavor. It's what gives thyme its flavor. What makes mountain mint so pungent. It's what makes a Monarda punctata, which is called 'Dotted Horse Mint'. Some of you guys might grow that. It's kind of aggressive but it's a wonderful plant for pollinators. But it's what makes them smell that way and it's why we use them in cooking, right, because we want our food to be flavored like that.

Plant Mint Family Plants for Fragrance and for Pollinators

Now how many people in here know that that's a deadly poison? Thymol all is very toxic, and some plants have so much thymol in it that if you use a lot of it, you'll get sick. Any of you guys do essential oils? Right, so oregano oil is just really concentrated thymol in there and if you use too much of that it can end you up in the hospital. Okay, so that that can be a deadly poison because it is poisonous in large quantities and that's why this plant has it. Almost everything in the mint family has these wonderful oils, aromatic oils, in them that are there for defense, right. And we can use those in small amounts to flavor food, but you wouldn't want to like chop up a bunch of this make a salad out of it and eat this poliomintha. That would really give you a bellyache if you did that because thymol's not that good for you in large doses. Matter of fact, you can't even drink that pure oregano oil. It burns your mouth really bad because it is so strong. So, mint family plants, when we start thinking about mint is just like the quintessential... if you want to encourage pollinators, mint family plants are some of the best plants for pollinators out there. Their flowers don't have the toxin to keep insects away but the plants themselves are often sticky. They're glandular. They have oils in them that we use and call it for culinary uses, but those culinary uses for us are deterrents against things like aphids, and mirids, and sucking insects, and chewing insects, and beetles, because when they bite into it, they don't like it very much.

It's like nicotine, right. Nicotiana. All the members in nicotiana have nicotine in their stems, members of the tobacco family. And the nicotine is there, not so somebody can smoke a Winston like Fred Flintstone used to do. Anybody old enough to remember when they had, they had cigarette commercials on the cartoon. They did, it was crazy. They did. Fred would be like - Hey Barney, you want a Winston the smooth flavor of Winston. So, I always think about that when I think about somebody smoking a cigarette. But it's not there for that. It's the nicotine is a natural insect repellent, insecticide and so we actually develop, I've developed, in the horticultural industry, a number of nicotine compounds that we use to treat plants as a systemic insecticide to prevent insect damage on plants over a long period of time. Now it also can harm pollinators. In cases, some neonicotinoids, but it's also the thing that keeps the few hemlock trees that are still alive in the mountains are alive because we've injected them with neonicotinoids that keeps the little insect that, the adelgids, that eats the hemlock from eating the hemlock. Okay, so when we think about culinary herbs - basil, thyme, rosemary, lavender, oregano, mint, peppermint, spearmint, penny royal, they're all in the same family. They're all mints, right, so very important.

Attendee: Is sage a mint?

Dr. McMillan: Sage is a mint. Salvia is a mint, yeah absolutely. So, mints, great example of that. So, we're going to look at a number... here's one though. This is like the scratch and sniff class. So, I've got one here that I really think is interesting. It's called Lepechinia hastata and you'll never guess what family it's in.

What's the only family we've talked about, right? Mint. So, it's from Baja in Mexico. One of the few plants that we actually get away with growing from that part of Mexico. But this one, I want you to... yeah... kind of brush the leaf a little bit before you smell it so that you get some of the oil moving, so you get the full effect. And then I know you're familiar with that scent. Doesn't it smell familiar?

Lysol bathroom cleaner. Does it not? It smells like bathroom cleaner, Lysol. Yes, it does. It does. Again, so not all mints have really pleasant odors. Some of them have fetid odors. Some of them have odors that are strictly there for getting rid of... Yeah, you can, you can, we can compost it. That's fine it's composted.

Attendee: I think my Lysol's not that strong.

Dr. McMillan: Yeah, it's crazy, isn't it? So, when you're developing a garden, you know, you sometimes you like to include plants that have flavor... you know have the odors that are pleasant to you. Sometimes you like to have something you can say - Can you believe this [ __]? This sounds like life's all happening, right? Yeah, it's just cool to be able to do that sometimes. Let's take a walk around a little bit and we'll look at some other things. I'm going to take us mostly through the shade today and we're going to end up in the in the heat over there.

Sometimes Fragrant Means Fetid

Pine-sol, Lysol, could be Pine-sol too. It's got, I mean, there's so many odors in that thing but it definitely smells like a disinfectant, doesn't it? Yeah, really very interesting. So, it's so much better in the shade. So, we really love this genus of plants which has no odor to it right now. But in the spring, these send up these giant weird flowers that look like a brown peace lily, kind of, or a jack-in-the-pulpit if you're familiar with it. This is the genus amorphophallus. If you know Latin, that's kind of a dirty name. But anyway, it's known most of the time as the common name for this group of plants is called corpse plant. And not all of them have flowers that smell like corpses but most of them do. Some of them don't smell like dead people, some of them smell like, oh gosh. Jeremy, how would you describe the odor of some of these things?

Jeremy: You'll probably have to edit it out later.

Yeah, they're bad. They're all bad and it's a great example of one of those plants that here, instead of odor being in the leaves, the odor is in this ridiculous huge flower or inflorescence really is what it is. And it's really taking advantage of animals. So, if you think about how in your garden deer and rabbit oftentimes take advantage of your plants, well plant one of these because it tricks flies so bad that thousands of them will go in there and they'll lay their eggs in the flower thinking that they're laying their eggs on some dead guy. And when the maggots hatch, they die. They starve to death. So, it's tricking. It's taking advantage of the pollinator and that type of pollination is called pollinator parasitism. So, this is a pollinator parasite. A plant that is parasitizing its pollinator by taking advantage of it. Forcing it to expend some of its energy and lose something of its own to gain fertilization of its seed. So, power to the plants, right.

Attendee: Amazing.

Dr. McMillan: Oh, it's crazy, all these things. I don't know if this has any scent on it yet, but hedychiums are among the most beautiful scent scented flowers you can put into your garden. Some of them. The orange flowered ones generally don't have a lot of scent but any of the white flowered ones, they do. And these are our ginger lilies, is what we call them, but they're white, right. And they're tubular.

Dr. McMillan: So, when do you think they produce their scent?

Attendee: Nighttime.

Dr. McMillan: At nighttime, yeah and they're pollinated by...

Attendee: Moths

Dr. McMillan: Moths, yeah, exactly. But they do have also... in their leaves you can smell a little bit of the gingery scent that tell you that it's in the ginger family. As things in the ginger family have a number of different oils in them that are specifically there for what?

Why would they have these oils like ginger? You guys all are familiar with the flavor of ginger root.

Why does ginger root have those really distinctive chemicals in it? Which I can never remember the name of, but i took a screenshot so I could tell you. It's pyrogallol p hydroxybenzoic acid, p-coumaric acid, and ferulic acid that they have in them that make them great. Great things for being medicinal plants. They're anti-cancer. They promote lots of healthy functioning in the body and they're also antiseptic and anti-bacterial. That properties that those gingers have.

Dr. McMillan: But why do they have those chemicals? So, we can be healthy and every time we get a little sniffle drink ginger tea?

Attendee: Just to ward off parasites, I guess?

Dr. McMillan: To ward off insects. Yeah, it's another great chemical that for us, it has a use. But if you were a little tiny insect and you were taking huge numbers of that, you'd be like, yuck, I don't want to eat that plant, right.

Attendee: Do hummingbirds like hedychium?

Dr. McMillan: Of course, absolutely hummingbirds love hedychium flowers because they're full of nectar. So even though they're naturally pollinated by moths. And you know why they're naturally pollinated by moths? These plants are from Asia. And how many hummingbirds are there in Asia?

Zero. All hummingbirds are new world. North and South America only. So, any plant in the old world that's pollinated by birds may have a red flower, but it also has a landing platform where the bird could actually land on the plant and get into the nectar. Because no other bird on the planet can hover except the hummingbird, right. So, kind of cool.

Lilies all smell really nice and spicy, right. And a lily is a really good example of a plant that is lots of nectar, smells really good, smells really spicy, and it tries to attract butterflies. So not a night flowering thing. It has lots of scent during the day and in the case of most of our lilies that are native they're pollinated primarily by swallowtails. The swallowtail butterflies got big enough wings to hit these anthers out here and transfer that onto the stigma. But with these little skipper butterflies, the silver spotted skipper that's just popping around right there. I know, they're like, they're the one butterfly that says - I'm so ugly nobody wants to catch me, so I don't care, I'll just hang out here. But they're too small to effectively pollinate that plant. They just simply land on the flower and steal the nectar, right. So interesting stuff. All right, there is a Zingiber mioga around here somewhere.

Oh, there it is. Right in front of me. Jeez whiz, there you go. Zingiber mioga. So, this is a very interesting plant to me.

And if I got any really brave folk in the audience here, we'll, you're welcome to try this. I'll show you; I'll prove to you that it's not trying to poison you. But this is the flower spike. The inflorescence developing of a Zingiber mioga. So zingiber is the genus of ginger, okay. And so, zingiber should smell like ginger and when you crush it and smell it, this is a true zingiber. Just like Zingiber officinale. It does smell just like ginger. But in Japan, what they will do is slice these flower buds and they eat them fresh. So, you slice it up and you make a salad sometimes mixed with cucumber, a little sesame oil, and a little bit of a little bit of soy sauce, and it's really, it's quite interesting and wonderful. So, if anybody's really brave, I'll pull off all the stinky brown spots on it. But you can try it. It's got a very unusual flavor if you want to pick a piece and try it, you're welcome to. But that gingery odor that it has is in the leaves. It's in that and it's there to protect it against herbivory, right. There to protect it against getting eaten. That's what I mean by sensory garden. I walk through the garden, I pick things, I eat it.

Attendee: It's not bad.

Dr. McMillan: It's not bad. It has just a slight ginger. Not really hot, very mild, but very distinctive. Some people say it has a taste of cilantro and after you chew on it a little while you might get that cilantro-y taste to it as well. Let's go look at some really stinky ones.

Attendee: We got all the good ones out of the way.

Dr. McMillan: Yeah, all the good ones are gone so...

Eat Your Garden Plants

The mioga has all the good compounds in it that make ginger and turmeric. It has lots of curcumin in it, so it makes it have all those health benefits that you get from ginger and curcuma. By the way, I was, when I was at Clemson, I was working with a couple of researchers on turmeric which has amazing anti-cancer properties to it as well. So, it's... I can't say enough about the ginger family. Plant lots of those.

Eat your garden plants. Here's an interesting one.

This one has an odor that is unique. It's not bad at all but it's unique and unless you've smelled fresh ginseng before, you wouldn't know that it smelled like ginseng, but it smells exactly like ginseng. It's in the same group within the carrot family. Ginseng’s in the carrot family, used to be considered the Araliaceae, now they're lumping them all into the carrot family. But yeah, it's very nice. So, this is a plant called spikenard and this is a very commonly cultivated one from Japan that's called 'Sun King'. We have a native one spikenard here, Aralia racemosa, has the same chemical in it. And that chemical is the same chemical that's in ginseng. It's the same active ingredients that, in traditional medicines, they think give ginseng the power to make you smart and make blood flow to various regions of the body. And it doesn't work. But this works just as well as ginseng. So why we continue to go out in the woods and dig up ginseng roots instead of, you know, use some other ginseng family things that are really easy to grow and like have the same extract. They all do the same thing, which is nothing.

But is an interesting odor, isn't it? You can start to figure out families of plants just by the types of odors that they have. Everything in the citrus family smells like citrus, you know. Everything in the ginger family has a little bit of gingery odor to it.

This is what I call penance for making you smell all those really nasty things. So here, smell some lavender.

Dr. McMillan: What family do you think lavender’s in?

Attendee: The mint.

Dr. McMillan: The mint family, right. Anything that we think, oh that's such a pleasant odor, probably in the mint family.

So, there's a term I'm going to teach you guys about plant odor today. A term for a particular type of odor. It's called fetid, okay. Oh, here's one. Here's one. Oops, you okay. Here's one that's easy to identify the family on.

Onion, right. Even though you might not even know what an onion flower looks like, onions have umbels of flowers just like milkweeds and carrots do but they're umbel, they're a monocot with a globe-like, usually umbel of flowers. And all of these plants in the onion family have varying levels of sulfur compounds in them that give them that smell like an onion.

And what do you think those compounds are in there for?

To keep things from eating it, right, right. So, for umbel, yeah so, an umbel is of the pedestals to each flower coming from exactly the same point. So, like an umbrella has all the spokes coming back to the common point, an umbel has all the all of the flowers coming back to the same point on the plant. So that's why we eat those, the sulfur compounds right. So, it's really the same things that are giving us the fragrance. Fragrance is such a part of our culinary experience that oftentimes the taste and the fragrance are the same the same chemicals.

Attendee: Is it that the sulfur compounds are thwarted or muted by the soil first? Like I'm thinking Vidalia onions.

Dr. McMillan: Oh no, it just has less of the sulfur compound and more sugars in it, so the sugars overwhelm those sulfur compounds. Yeah, yeah, now I mean I'm from a Jewish family, so we don't like Vidalia onions, we like the really stinky hot ones, you know. But yeah, some, not everybody likes Vidalia onions. We always cook with Spanish onions. Those yellow, kind of tight ones, that have lots and lots of sulfur in them. This one's interesting. Okay and this is one of those plants where remember, I just gave you lavender and remember the lavender.

This is Cucurbita foetidissima. Fetid. Remember the term I told you I was going to get you to remember? Fetid just simply means bad. It means either like rotten meat or body odor, like this. Yeah, so once you've, when you smell the plant up close you may think – Oh, it doesn't really smell like body odor -but then smell the fingers that touch that. Oh my god everybody's going to think you didn't take a shower today.

Papa John's, it kind of does it kind of does smell like Papa John's pizza crust, yeah, yeah. Yeah, maybe it smells a little like Papa John's. Oh shoot. I was going to pick an Iris foetidissima that also has a really fetid odor to it but let's go to something a little more sweet.

Oh, there's a good, this one's a good, this one's an interesting one. Let's look at this one. I almost forgot. So, these flowers on this plant. This is Cestrum parqui, okay. It's from Chile and it's called like Chilean Jazz, Bush Jasmine, or what did... cestrum is what we call it. But the flowers smell incredibly sweet at night. This is another moth pollinated species so at night they smell incredibly sweet, but they have no odor during the day. But what I want you to smell, is the leaf. And think Jiff or Peter Pan.

Attendee: Oh wow!

Attendee: Oh, my goodness. Really ...

Dr. McMillan: Smells just like peanut butter, doesn't it? Isn't that crazy?

Attendee: Wow!

Dr. McMillan: Yeah, so this plant is in the same family as tobacco. There are chemicals that make it smell like peanut butter. Guess why they're there? To protect the plant from herbivory, again. Something that may smell good to some people unless you don't like peanut butter. This is one of the more unusual, I think good, smells but some people like, it some people don't.

So sage is now in the genus Salvia, so many things are in the genus salvia now. Salvia are all mints and this one has so much oil in it, it grows, it's native to the deserts of central Mexico, and it has so much oil in it that you won't have any problem feeling it. This is Salvia darcyi and you can smell, it's a very unusual smell, but salvias all have unusual minty smells that are complex. That's why sage, we cook with it with things like meats, like lamb, and and those types of meats is to give them the complex flavor to complement their already complex greasiness of lamb. But you know it's... you don't use it on everything, right. And those are some of the complex odors that you can get from salvias in your garden. Every single salvia that we have, every single salvia we grow, has a different odor. This one, I think, is the coolest to me.

Attendee: I heard that one can raise your blood pressure.

Dr. McMillan: That Salvia darcyi, or sage in general?

Attendee: Sage in general.

Dr. McMillan: Oh, sage in general can, yeah. And so, you just, what you do is you put some of the mioga in there because that actually lowers blood pressure. It also is an insulin, it stimulates insulin processing, so it's good for diabetics too. So um, you can just put mioga in with your sage and you've corrected everything, right. It's all about balance in life. So anyway, I really just wanted to give you guys an idea that there's so much out there. When you're picking a plant, when you're choosing a plant, don't ever just say - Oh, I like the way that looks. You want to touch it, you want to smell it, you want to feel that plant and see you know how deep an experience and how intimate an experience that really interacting with your plants and gardening can be. And those are just a couple examples in the 15 minutes I turned into 30. Thank you. Any questions from anybody? All right. Do you have any questions?

Attendee: Where are we now? At the edge of the sun garden?

Dr. McMillan: Yeah, so no, you're actually at the edge of the 41 of the other shade garden and the sun garden would be down the road and back across. Yeah, back across to this side. Okay. All right. Yeah, my pleasure. Thank you. You guys have a great afternoon. Thanks for coming.

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