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Brian Lehrer: Brian Lehrer on WNYC. Now for our March check-in with trees, it's month five in our year-long project to follow the life of a tree through the four seasons, looking at and learning about the trees around us, what they do for and to us, and what we do for and to them. We hope you picked out the tree you want to follow and maybe even tweeted us a photo using the #BLTrees.

It was snowing, at least in my neighborhood, last night, but we're less than a week away from the spring equinox when days are as long as nights and soon to be even longer. We're going to talk about how the changes and light and temperature trigger growth and flowering in the trees that have been laying low all winter. Back with us is our guide for this adventure urban ecologist, Marielle Anzelone, founder of New York City Wildflower Week who proposed this project and has offered her expertise in putting it together. Hello again, Marielle.

Marielle Anzelone: Hi, Brian. Good morning.

Brian Lehrer: Today she is joined by Georgia Silvera Seamans, director of the Washington Square Park Eco Project and founder of the group Local Nature Lab, also a member of the Black Botanist Week. #BlackBotanistWeek organizing committee. Georgia, welcome.

Georgia Silvera Seamans: Good morning, Brian. I'm so happy to be here.

Brian Lehrer: Listeners, if you have any quick update on your chosen tree, our phones are open at 212-433-WNYC, 212-433-9692, or tweet @BrianLehrer. Marielle, of course as you know because it was your idea, we've asked the listeners to pick a tree to follow through the course of this year-long project. I took a quick glance at the tree on my block that I'm following, this pear tree, and I don't quite see it budding yet. Are buds popping in places around here?

Marielle Anzelone: They are, and with some trees, it'll depend on the species of tree and what they respond to. For example, what's popping right now are red maples. Red maples are in flower, which is so exciting to be able to talk about flowers finally. Red maples are one of the earliest trees to flower, and they have these beautiful red flowers and they're really easy to see now because there's really nothing else to look at. For some other trees, like I'm following a pin oak and I noticed today that the buds are elongating. They're not quite ready to pop, but they will be really soon.

Brian Lehrer: Now, Georgia, what's happening as the season changes? Is the sap flowing, pollen dispersing? What's happening biologically with the trees here in mid-March?

Georgia Silvera Seamans: That's a really good question, Brian. There are lots of things happening. As Marielle said, it really depends on the species. Some plants might respond more to increasing light, and some might respond more to increases in temperature. Some might rely on a combination of both those things. It really depends on the species. We know that with the early flowering species, like red maple is one example, they are probably more sensitive to temperature than to light. I know in Washington Square Park, the silver maple is almost done with its flowering season, and the red maple is about midway.

Let's see. One of the trees I tweeted about, the Cornelian cherry which is a introduced species of dogwood, it is flowering, approaching maybe peak for the particular tree that I'm looking at, but one thing to consider is that even within species there's variation, so there are other Cornelian cherries in Washington Square Park that are a little behind the tree that I'm actually looking at.

Brian Lehrer: You've both mentioned the red maples. Georgia, they're not the same trees that make maple syrup, are they?

Georgia Silvera Seamans: Well, the tree that's used most for maple syrup is the sugar maple. You can tap other maples and I believe you can tap other species of trees, but the red maple, I think its flowering period is too early in the winter to really afford the kind of sap run that you need for sap production for maple producers.

Brian Lehrer: Now, Marielle, you use the word phenology in describing today's topic. What is that exactly?

Marielle Anzelone: Phenology is such a lovely word. Essentially, it's marking the passage of time through nature. Spring, everyone's so excited because tree buds are opening, flowers are blooming. These are things we think of when we think of spring, and they're natural markers of time. It's seasonal change that we see in living organisms. For trees in spring, we'll see, as we mentioned, looking for leaf buds to break which are either going to have leaves or flowers. Then in summertime, the leaves will be a darker green and fully extended to their full length. In autumn, of course, we have seasonal color change in deciduous trees, and then winter is marked by dormancy and tree loss. All of those things are part of what we would call phenology.

Brian Lehrer: Here's a tweet from the listener that says, "Happy March from Holmdel Ginkgo." That's Holmdel, New Jersey I presume and somebody's ginkgo tree. "Signs of the promise of the beautiful ginkgo leaves to come." Complete with a photo from one listener. Georgia, I've read that there are male and female ginkgo trees and one of them makes a better street tree, I can't remember which. Are you familiar with that?

Georgia Silvera Seamans: I am. The ginkgo biloba is a dioecious species. In the case of the ginkgo, individual plants are either male or female. In New York City, I believe it's the mid-1990s that the city began specifying that only male gingko trees could be planted because the males don't bear fruit. I have to say, though, many of those are probably cultivars. I think with ginkgoes because they don't bear fruit until a certain age, in a young ginkgo tree it might be hard to tell whether it's male or female unless you're working with a known cultivar so you know you're getting a male every time. I want to add to that, actually, because there are male trees that have been known to change sex, and so they will bear fruit not on the entire tree, but maybe a branch or two.

Brian Lehrer: You can't do that in Texas, I don't think, but that's another show. In fact, that's tomorrow's show.

Georgia Silvera Seamans: I think so.

Brian Lehrer: Listener Tulis, we thank Tulis for the photo that they just posted of their current tree. It says, "Here's my American Elm at the edge of Saint Nicholas Park, February, 2022." The branches certainly look bear. Marielle, do many trees have different sexes, and do they respond differently to spring?

Marielle Anzelone: They do. I don't think it's the sexes of the flowers that are related to phenology, but it's the time when we see these. Yes, trees have very complicated sex lives as Georgia mentioned. For example, the red maple is polygamodioecious, which means that some trees, the entire tree is female, and so they would produce flowers that would turn into the samaras, which are the fruits known as helicopters, and some are entirely male, they produce flowers that have pollen but don't produce fruits.

Now some trees though are monoecious, which means that they have both male and female reproductive parts on the same plant but in separate flowers. Red maples are what we would call functionally peltandra, which means that male flowers bloom first and then female flowers bloom. Currently, in New York City, I've seen mostly female flowers blooming now, the males are past bloom, but you can see the males really easily because they're the ones that have the yellow [unintelligible 00:09:36] on them. You can see it with your naked eye and the females tend to be only red and the flowers there are a little bit smaller.

Brian Lehrer: We're getting a call about the colors of some trees, and I'm going to take this call. Carol in Manhattan, you're on WNYC. Hi, Carol. We've only got about 30 seconds for you, but you have an interesting question here. [crosstalk] Go ahead.

Carol: Hello? Hi. Thank you for taking-- Yes, can you hear me?

Brian Lehrer: Yes.

Carol: My question is about since mid-winter, a lot of trees in Central Park, and I don't know the name of the tree, the limbs seem to have turned like a grayish white color, and I'm wondering if your experts there know what that is or what the trees are and what was happening to them?

Brian: Georgia, is that familiar to you?

Georgia Silvera Seamans: That doesn't sound familiar to me. [crosstalk]

Brian: Marielle, B=briefly.

Georgia Silvera Seamans: It would be helpful to know the species.

Marielle Anzelone: Yes, it would be really helpful to know the species. No, I don't know. Having a grayish white coating, it could also be lichen, which are-- we welcome lichen on trees. Lichens are indicators of clean air and they don't hurt trees at all, they're simply looking for things to grow on. It could also be some kind of mildew or fungal infection, and those depend on the type of tree. Specific tree species have specific fungal infection, so there's not really any way to know, but if she could follow up perhaps and tweet it to the #BLTrees, that would be really helpful, with a photograph, and then we can follow up.

Brian Lehrer: We can respond. Georgia, in our last minute, I know you're tracking the changes of 13 trees in Washington Square Park. You want to tell people what's involved in that, and if there's a way they can join you or follow along?

Georgia Silvera Seamans: Sure. We use the Nature's Notebook app, which is a project of the National Phenology Network, and anyone can do download the app and participate. They can certainly reach out to me if they want to be trained in using the app in the park. We, myself and some volunteers, that change over the time of the project, we go out on a regular basis, meaning in the winter and the summer we go out once a month because pheno phases aren't dramatically changing. In the spring, on the fall, we go out once a week and the app is really easy to use. It tells you what to look for. There are photos, there is lots of information if you forget what something means. It's a really fantastic way to take notice of plants in the city that you might otherwise walk-by.

Brian Lehrer: With that, we are out of time. Georgia Silvera Seamans, director of the Washington Square Park Eco Project and founder of Local Nature Lab and Marielle Anzelone, urban botanist and a colleger and founder of New York City Wildflower Week, we'll keep doing this every month until November. Marielle, talk to you next month.

Marielle Anzelone: Thank you so much, Brian.

Brian Lehrer: #BLTrees, post your photos. Brian Lehrer on WNYC.

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