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Brian Lehrer: Brian Lehrer on WNYC. Now for our second check-in with your chosen trees in our year-long project called #BLTrees. In case you missed it, last month, we kicked off this 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. New York City itself has at least a million trees, we hope you pick the one that you want to follow, and maybe even tweeted us a photo as many people have using the #BLTrees. I tweeted mine yesterday, what it looked like in early November and what it looks like now. Back with us is our guide for this event adventure urban botanist Marielle Anzelone who proposed this idea. Hello again, Marielle.

Marielle Anzelone: Hi, Brian.

Brian Lehrer: She is joined today by Regina Alvarez, assistant professor of biology at Dominican College, who was the Director of Urban Horticulture and Woodland Management for the Central Park Conservancy. Welcome, Professor Alvarez.

Regina Alvarez: Thank you, Brian.

Brian Lehrer: Marielle, to start out, I understand you've been counting up the number of tree photos. How many of our listeners have taken that extra step beyond listening, and maybe started looking at a chosen tree more closely?

Marielle Anzelone: Yes, we had a lot of people. People were really excited about it, and a lot of people shared a lot of sweet stories as well, but for photos, we had 98 people share photographs. A number of people shared more than one tree, they got really into it. One person shared nine different trees. She really kept me on my toes.

Brian Lehrer: Wow. What were some of the things, remind everybody, that you had us looking for since this is a monthly check-in between November and December specifically?

Marielle Anzelone: Right. The idea is to take a closer look at the trees that are around us and to choose a tree that felt easy, that you could get to easily, or maybe something that was like, "Oh, I really want to visit this park once a month, and having this tree will incentivize me." In looking at the tree, the best thing to do, especially if you want help with identification, is to take a photograph of the leaf if it still has one, bark, and the entire tree. It also helps to include a geographic location, which some people didn't do, which made it a little bit harder, but I think we did a pretty good job of identifying most people's trees.

Brian Lehrer: Listeners, if you're already participating in BL Trees, why don't you call up and tell everybody else what you noticed about your tree in the last month, or anybody who has a question for our guests about your specific tree or trees in general in the month of December, give us a call 212-433-WNYC. 212-433-9692. Professor Alvarez, one thing we'll notice about the tree pictures this month is that there are many fewer leaves. Can you explain a little bit about what actually happens with non-evergreen trees? Are they, in effect, hibernating?

Regina Alvarez: Yes, in a sense, that's what they're doing. In our area, since it gets cold here normally, in the winter times, there's less water, it can be tied up as ice. The trees have evolved ways of sitting out the rough weather, and dropping their leaves is a very good way to conserve water. It's much more of a process than people realize because the trees have to, when they drop those leaves, they have to block off that little spot where the leaf was connected to the tree. If you look closely, it leaves a distinct scar that gets covered with these quirky cells so that fluids don't leak from that spot. It's really pretty fascinating process.

Brian Lehrer: Marielle, on tree identification, I'll ask you my own question here, you saw that I tweeted two photos of my tree yesterday, the one in my neighborhood that I've chosen to follow. You told me that it's a kind of pear tree, and I was like, "Pear tree? It doesn't ever produce pears." Is that a common thing in New York, pear trees?

Marielle Anzelone: Yes. The tree you have actually [beep] is pear. Your tree is a Callery pear. It's the second most common street tree planted in Manhattan. It's very commonly planted. The reason why is because there is this idea that being a street tree is pretty stressful. It has to deal with a lot of things like air pollution, assaults, soil compaction. This tree was cultivated by the government to deal with all of those stressors. The Callery pear is very commonly planted, it does produce pears. In the spring in April, you'll notice it has like beautiful spray of white flowers, and people just love it. Then later on, it produces, but they're very tiny, so you probably wouldn't notice them, but birds really like them and eat them. It definitely does fruit, but they're only about half an inch big. Yes, they're pretty small.

Brian Lehrer: I guess I never recognize those little things as pears as humans usually think of them. Are they edible by humans?

Marielle Anzelone: You know, I don't know. I wouldn't encourage anyone to try, but the birds definitely really like them. Another thing about the Callery pear is it is so beautiful, but there's a couple of problems with it. One is that it's been shown to be structurally weak, where when there's a heavy ice or snowfall, the branches can break off. It's not planted as much anymore. Another problem with it is that it's actually really invasive. You can see places where the trees have entered into natural areas because the birds do eat the fruits and then poop them out as they're flying or in a natural area, and that's how they spread through the landscape.

Brian Lehrer: That would be the "partridge in the pear tree", right?

Marielle Anzelone: Yes, exactly. You can really see in April, how much the spread has devastated natural areas because you just see this like long patch of bright white flowers.

Brian Lehrer: Marlene in Brooklyn, you're on WNYC. Hi, Marlene.

Marlene: Oh, hello. How are you?

Brian Lehrer: Good. What's you got?

Marlene: I'm calling about my crab apple tree that loses its leaves in August. I've had it pruned twice, and there's a cedar tree in the neighboring backyard, which I believe is causing this problem. I don't know what more to do. I did have it sprayed once.

Brian Lehrer: Professor Alvarez, is that something you can address? Have you heard of that problem? Could the kind of one tree be causing a problem with the other kind?

Regina Alvarez: What that is is a fungus. A fungus is actually what's causing the problem. The reason the other tree is causing the problem is because this fungus has a lifecycle that requires two different species to fulfill its lifecycle. It spends part of its lifecycle on her crab apple tree and part of it on the cedar tree. It's called cedar-apple rust. It's a really interesting fungus, but if you're growing a crab apple tree, you may not be very enamored of it. Other than then spraying it, I am not sure, just make sure to clean up the leaves that fall because they may harbor some of the spores. Having junipers and cedars nearby apple trees and other plants in the rose family can lead to having this cedar-apple rust problem.

Brian Lehrer: Leslie in the Bronx has a question about a tree. Hi, Leslie.

Leslie: Oh, I don't have a question. I have a story.

Brian Lehrer: Oh, good.

Leslie: I have been photographing the tree outside my bedroom window for over a year. When you mentioned on your show last week or so that you're going to start this project of having people photograph a tree, I started doing it with the tiniest buds coming out, till all the leaves came out, and then I found that there was a bird's nest on the branch, and then another bird came in and attacked it and tore the bird's nest apart. I photographed all of this stuff. It was my COVID project over the past year. Then this huge windstorm came along about a month ago and tore that branch clear off the tree down into the backyard of my building.

Now this tree is taller than the seven-story building, but now I just have the little bud of a smaller limb coming up outside my bedroom window, but I was so thrilled when I heard you suggest that people photograph a tree over the course of a year because I've done it and it's really, really fabulous to watch little buds come up, then the leaves, then they fall off, and then the snow, and all the nooks and crannies of the branches. It's really fascinating.

Brian Lehrer: That is great. What a great story and well told, Leslie. Thank you very much. Professor Alvarez, why do the leaves fall off the trees at different times? Like my pear tree, it still has leaves, and well into November, it's entirely green, which is past what a lot of people consider fall foliage season.

Regina Alvarez: Well, there are a couple of factors. One is depending on the species of trees. They've each evolved differently to react to different temperature. Some of them react to day length, the amount of light every single day. It could be from species to species, they drop their leaves at somewhat different times. The other factor are what are called micro-climates. Your tree, if I remember, I saw your photo, it looks a little bit protected by the buildings around it. It might feel a little bit warmer there. I've seen gardens that are next to buildings that get warmth from the buildings or sort of protected from the wind, they could be a week or two weeks later in their phenology, in their showing of what time flowers or what time they fruit or what time they drop their leaves. It's a combination of species and their local environments.

Brian Lehrer: Interesting. Conditions. Lisa in Forest Hills, you're on WNYC. Hi, Lisa.

Lisa: Oh. Hi, Brian. Thank you for taking my call. I'm the culprit with the nine trees.

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Lisa: They're all in Forest Hills.

Brian Lehrer: Super participant. Go ahead. They're all in Forest Hills.

Lisa: It's so fun. Most of the trees are in the garden. There's one that's on the other side of Queens Boulevard, but my question is, I've heard that trees have gender, and is that correct? If it is, is it correct of all trees? Is there a way that a average person like me can detect that, or do you need like a lab coat and a X-ray?

Brian Lehrer: All right. Marielle, are there male trees, female trees, non-binary trees?

Marielle Anzelone: Yes, there definitely are. It depends on the kind of tree. Different species have different reproductive strategies. In some cases, a tree may have the male and female reproductive parts within the same flower, and so when we think of a flower, we think of the petals and it looks really pretty. Well, the petals are just like a window dressing. That's not the important part of the flower. It's the little things in the center. There's the male and female parts, and if they're both on one flower. Some plants have just the male parts on one different tree. Ginkgos are like this. One tree might be male and once we might be female and you know the female because they're the ones that have the large seeds that are odiferous that drop.

Yes, it really depends on the species of plants. The trees have all kinds of different reproductive strategies. Some flowers first emerge as female where the pistols are exerted, and then later have the anthers exerted, which is the male part. It can also be a timing difference in whether it's male or female.

Brian Lehrer: Are the female trees less prone to violence? Oh, never mind. That's another show. Nora on Staten Island, you're on WNYC. Hi, Nora.

Nora: Hi. This sounds like a lovely project. I have two questions. First, in the last couple of days driving around, I've noticed a couple of trees seem to be budding, and I noticed two and there were two different kinds of flowering. Not really flowering, but two different kinds of growth on them that appear to be spring-like, and so they'd be two different types of trees. My second question is I have a dogwood in my front yard that's at least 55 years old, and for the first time this past spring, it did not flower, and I was wondering if you could explain why.

Brian Lehrer: Thank you. Professor Alvarez, it's been in the 50s this week in December. Is Nora's tree there fooled into thinking it's spring and starting to bud?

Regina Alvarez: This is the time of year when they're forming their buds and the buds are growing. They do look more and more obvious as the season goes on because that embryonic leaf or flower, because there are two different types of buds, it could be a leaf bud or a flower bud, is growing and it's protected in there. If they haven't opened up, they're fine. They're doing what they're supposed to do. Some plants, with this warm weather, do get fooled and they do open up. If a flower bud opens up, you lose that flower for the coming spring.

Brian Lehrer: We've just got 30 seconds left. Marielle, this month two of our monthly check-in with our chosen tree. What should people look for between December and June?

Marielle Anzelone: Well, take a close look at bark. The leaves are gone. We're going to be looking a little bit more closely at what's left behind. Bark, maybe some little pieces of fruits that are left, but definitely look at trees, if you can, with a magnifying glass, use your hands, rub them around the bark and get some ideas about texture and color. Yes, it's a fun time to actually take a deeper look at trees once the leaves are gone.

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Brian Lehrer: Listeners, take a photo of your chosen tree and tweet it to #BL, as in Brian Lehrer, #BLTrees, and we thank Marielle Anzelone, urban botanist and founder of New York City Wildflower Week. She'll be back with us next month, and our special guest today, Regina Alvarez, professor of biology at Dominican College. Thank you both so much.

Regina Alvarez: Thank you, Brian.

Marielle Anzelone: Thank you, Brian.

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