an eco-focused fall cleanup, with native plant trust’s uli lorimer

WE’VE ALL HEARD the environmentally conscious advice: The way we used to clean up our gardens, extra-tidy, but to within an inch of its life for every unseen beneficial creature out there trying to tuck in for winter, is not the best practice. I’m learning and evolving my approach as I go the last few years, reading up about guidance like “leave the leaves,” and cutback strategies like “chop-and-drop” and more.

And asking experts for help, including today’s guest, Uli Lorimer, Director of horticulture at Native Plant Trust.

Uli, author of “The Northeast Native Plant Primer,” has made native plants his career. In 2019, he became director of horticulture at Native Plant Trust, America’s oldest plant conservation organization. And before that he was longtime curator of the Native Flora Garden at Brooklyn Botanic Garden. (Above, frozen dew on Panicum virgatum; Uli Lorimer photo.)

Plus: Comment in the box near the bottom of the page to enter to win a copy of Uli’s “The Northeast Native Plant Primer” (affiliate link) part of a series of regional editions that also includes Midwest and Southeast ones—so if you live in one of those regions, take your choice of prize.

Read along as you listen to the Oct. 31, 2022 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on Apple Podcasts (iTunes) or Spotify or Stitcher (and browse my archive of podcasts here).

eco-focused fall cleanup, with uli lorimer



Margaret Roach: Hi, Uli, and welcome back. Thank you for coming just in time for fall cleanup. You’re going to help me, right [laughter]?

Uli Lorimer: Yes, yes. Thank you for having me on again. Always a pleasure to speak with you.

Margaret: So you brought a rake [laughter]?

Uli: Yes. Well, I mean, I need an umbrella today, but yes.

Margaret: Oh, you’re having rain, O.K. By the way, I saw your byline in another place, or “byline” in quotes in another place too not so long ago, not just on the book. But I also saw on these native plant Folding Guides from the publisher, Earth Sky + Water, these sort of laminated multiple-panel guides that you can fold up and take with you to ID plants and insects and all kinds of things. I saw that you did some of those. Was that fun?

Uli: Yeah, it was a lot of fun. It was a fun project that kind of got squeezed in the beginning of the early days of the pandemic and surprisingly that there wasn’t a wildflower guide for the Northeast. Lots of bird guides and insect guides and butterfly guides and so forth. But it was fun. It was challenging, because you have very little space to write a description and you want to write something that isn’t immediately apparent with the illustration. So I found that was a nice challenge and I’m really happy with the way that the guide turned out.

Margaret: Yeah, well I’ll show with the transcript, I can show the link and people can look at those. They’re wonderful. So I have them and they’re wonderful. A cheat sheet, kind of.

Uli: Yes.

Margaret: And weatherproof [laughter].

Uli: Yes, indeed.

Margaret: So the first serious round of leaves dropped big time here where I am this week and zone 5B, and there’s lots more to come. But it’s “cleanup time.” And you’ve worked at public gardens through your career and I suspect that there’s a tension between sort of aesthetic and our increasingly ecological understanding, even if it’s… well, especially if it’s not at a place like Native Plant Trust and its properties that’s heavily ecological. But you probably understand that tension: You want to look great for the public, but you want to do the right thing for nature. So let’s just sort of talk about that a little bit. [Below, Cornus florida, now called Benthamidia florida, and Fothergilla by a path at Native Plant Trust’s Garden in the Woods; Native Plant Trust photo.]

Uli: Yeah, I mean I think it was really apparent during my time at Brooklyn Botanical Garden because nearly every inch of the 52 acres there is cultivated, and there are extensive lawn surfaces, and kind of an expectation that the lawns look clean, almost like a green carpet to contrast what’s happening in the beds.

And the approach there was either to shred them in place, or we had these little vacuum attachments to the riding mowers where we could suck them up. They’d get shredded a little bit. And then for the gardeners that were interested in shredded leaves, the grounds crew would come around and dump a load wherever you wanted these nice shredded leaves that you could then put back onto the bed. So we did really try to keep all of that resource on-site. So whether they were shredded, or whether they became a leaf-mold pile that might get used later on in making compost or in potting soils, that was the approach.

And I think that, fortunately at Native Plant Trust and the Garden in the Woods, we really don’t have much in the way of lawn surfaces. So it’s not that big of an issue for us. But I recognize that many people do have lawns, and I don’t see really any issues with cleaning up the lawns, as they were.

What I think the bigger issue becomes is when people feel compelled to clean out the leaves from the garden beds. I was just having a conversation recently with somebody who, for years and years, would rake out the beds, shred the leaves, and then put them back on the beds [laughter].

And I asked her, I said, “That’s a lot of work.” You set yourself up for a lot of work to put down things that are just fine if you let them stay where they fall. And that really gets at the balance that people have to strike between aesthetics and what we’re understanding as ecological function for that layer of leaf layer.

Margaret: So I mean, Doug Tallamy of University of Delaware, who’s written so much to increase our awareness of the ecological importance of practices and plantings and so forth, he calls these tactic of doing enough so that someone knows it’s a “garden.” He calls it a “cue for care.”

And Rebecca McMackin, who I know is a friend of yours, a colleague of yours, who was at Brooklyn Bridge Park for many years, she also would talk about how in that public space they’d kind of maintain the edges and keep the edges looking tidy, obviously the paths and things like that. Do you know what I mean?

So that you could say, hey, again, like Doug says, a cue for care—a hint, but without destroying the ecological value.

Uli: And I think that’s a really wonderful nuanced approach because it doesn’t take that much to create distinctions between a path surface or the leading edge of a bed and allowing for what all of the experts talk about that the “messy” is actually what nature wants. And leaving that a little bit further back in the bed.

Because the other thing, which is, I would say perhaps a bigger topic, but folks are very quick to deem spaces untidy, or even overgrown. That is sort one of my personal pet peeves about overgrown, because it comes from a place of saying that there isn’t that cue for care if you can’t immediately see it. And then it gets used as justification to come in and clear or tidy.

Why not look at a space like that and say it’s bursting with life? Look at what this particular patch is capable of sustaining, even if we don’t find it immediately aesthetically pleasing, doesn’t mean that it needs to be reigned in or cut back, or any other things that we do to gardens.

Margaret: Right. So we’re not only evolving our cleanup regimen, our protocol, our tactics, but we have to also start to adjust our vision a little bit so that we see a little bit differently about what is cared for and looks good and so forth.

So you were just talking about lawns. And you can’t just leave—especially like oak leaves—a whole sheet of oak leaves across the lawn areas. And hopefully we’re reducing our lawns, so this is less of an issue for us because we’re planting more diverse things in place of the miles of lawn. But you talked about further back in the bed leaving things.

And so I have, it began as almost a collector’s garden with many non-native plants included in it 30-plus years ago. And now there’s a lot more large-scale native plantings and so forth.

But in the areas that are where I have tiny bulbs that come up early in the spring, Eranthis, or snowdrops or whatever, I’m not going to leave three inches thick of leaves on top of those. I’m going to tease that off, because I know those babies want to come through early. And in a big, heavy wet mess, they’re not going to be able to.

But at the, say, the perimeter of my property and under big native trees, especially the oaks, I’m really making almost safety zones where I’m not cleaning up. Do you know what I mean? Where I’m doing more what you said. Is that kind of what you’re saying to us that we should do is to map out areas where we can let it all hang out [laughter]?

Uli: Yeah, I mean let’s consider this perspective: that if you observe plants that can grow strongly, so things that are able to push through that thicker strata of leaves, then those are good places. If you notice an area where the wind blows them in, maybe it’s a little depression or something where they naturally accumulate, then that’s the place to try to design for that condition.

Margaret: Oh, that’s such a great idea. That’s such a great idea.

Uli: So the converse of that is then if there are places that are naturally thin and windswept, if you would like, maybe where there’s a moss patch or something, those are places where you can start working with some of those more delicate, smaller, diminutive plants. The kinds that, as you indicated, would be smothered if it were under too much leaf litter. And to that effect, too, I think that for folks that either hire services or use services or use equipment like blowers, to also think about where you blow the leaves year in and year out.

Margaret: Yes.

Uli: Cause that’s another thing. At Garden in the Woods, we have this one section of the garden, it’s transitional space that we call Laurel Bend. And it traditionally had much more mountain laurel, but they were in decline. And so we started investigating a little bit, and it turns out that some of the stems were buried in nearly 12 inches of leaf litter. And it was apparent because every year when you blew off the paths to make the paths tidy, you kept blowing it and into the stems would catch the leaves, and then they would sit and then the next year you would do it again and again. And so they were accumulating at a rate faster than what nature would’ve done.

Margaret: And they were suffocating plants. Yeah. And the natural duff layer that would’ve come from the maybe deciduous trees adjacent or above that would’ve been a much lighter duff layer than this manmade debris, so to speak—pushing debris out of the way.

Uli: …From one place to another. And so the way that we approach our operations and management of the space is we’re trying to be more conscious of those kinds of situations where traditionally wouldn’t put the leaves in the same place every year. Maybe that’s a spot where we rake it into a pile and pick it up and move it to a mulch pile or something. And then there are other areas where you can disperse the leaves with a blower without any concern.

Margaret: Yeah, I mean I don’t think there’s any one-size-fits-all guidance here for every landscape. It’s these types of insights that you’re saying, like looking for spaces where the leaves naturally accumulate and thinking about maybe letting that be a wilder, messier place and so forth and so forth.

Uli: Or designing your garden to include plants that don’t mind coming through a thicker leaf layer.

And to say that we have fairly extensive areas with woodland phlox and creeping phlox. So in the winter it’s almost like a basal rosette, a groundcover. And so we found that it actually likes a little bit of leaf protection, of insulation over the winter, but then it’s something that we’ll tease off most of in the springtime so that it won’t have to struggle through the thicker layers. So that’s another approach.

Margaret: Yeah. So talking about then the other aspect, besides leave the leaves, as I mentioned I think in the introduction is that sort of chop-and-drop: the perennial cutbacks and doing that a little differently where we do need to do it or want to do it. And it used to be you’d cut everything down and that was it. And sometimes you’d put on a little fresh mulch or whatever, but it was just to with an inch of its life.

And now we know that standing material is tons of bird food and over-wintering sites. Similar to the leaf litter, it has all this ecological advantage. Are there places where you do cutbacks? And do you do them in stages and phases or?

Uli: Yeah, I would add that I think there’s also a growing awareness of the aesthetic benefits of leaving up seedheads. [Below, showy goldenrod, Solidago speciosa, left standing; Uli Lorimer photo.]

Margaret: Yes.

Uli: So there’s more three-dimensional structure, rather than this idea of a fresh start in the spring, where everything comes out of the ground at the same time. We have a of small grassland that we manage in that way, in which some plants get cut back. Others that we think have stout stems and seedheads that are attractive, we’ll leave in place.

We tend to cut things to a maximum of 18 inches, but nothing less than that. Because those stems… This was something that was kind of an aha moment for me recently: that not every perennial stems hollow, at least when it’s actively growing. Some have a hollow cavity, many have a pith. And so the insects that nest in those, they don’t actually nest in like this year’s-

Margaret: Right; still tender. Right.

Uli: It takes time for that cavity to develop. And so that’s why it’s important to leave those things up, standing, or even, as you said, cut and bundled or cut in dropped nearby to allow for those cavities to develop. And that is what the insects are after the following year and the year after that. So that’s something I think is also important that having those stems, you can bundle them if it’s more aesthetically pleasing or you can leave them where they lay. And next year’s foliage grows through all of it and it gets hidden in a hurry. By May, you never know what’s under there, but the insects do, which is the important part.

Margaret: Right. So if you’re leaving things up 18 inches or whatever, so like meadow management or you said a grassland—areas that are lots of perennials in close proximity. Again, speaking to Doug Tallamy’s advice and so forth, he would say, well if you can, cut back a third of it every year, not all of it one year,” because to your point then you’ve always got some standing stems that are 18 inches or more. Do you know what I mean? That are going to ripen or harden and become those places of refuge for stem-nesting bees and so forth, that you’ve got different ages of material. So that’s another idea, is to shift, to do it on a partial basis, as either to cut it back part way or to every year, cut a chunk of it back, I think is another way to go about it.

Uli: No, I mean it’s sound advice. I think you can also, from year to year leave different clumps of things standing so it’s not always the same thing. And that helps to spread out that resources as Dr. Tallamy suggests.

Margaret: Yeah. So this sort of chop-and-drop that we were talking about. So if we do reduce the height of something, we’re leaving the trimmings in smallish pieces beside the parent plant. So seeds are getting to the ground and they’re still there for someone to eat and there’s debris for them to tuck into and so forth. So it’s not carting it away on a tarp to the compost heap. Is that your approach there?

Uli: Portions of it. Again, I feel like as we talked about earlier, there is this friction between aesthetic and how people, how they conceive of that in their gardens, and the desire to maximize ecological function. And I think that threshold of, “How much of this can I tolerate?” is going to be different for some people. And we’re hoping that people will increasingly be more tolerant of, let’s say half of the debris is staying and maybe the other half gets carted away or three-quarters of it. But it in the end becomes, as so many things in gardens, a personal choice.

Margaret: Yeah. And my place is a couple of acres, so it’s different from a lot of smaller places. But then again, you’re talking about how many acres are you there at Garden in the Woods?

Uli: We’re at 45.

Margaret: Yeah, so it’s a whole different scale. But what I’m finding is because I’m an old gardener, I learned the old traditional ways. So what I’m finding that for me is the easier evolution is I’m identifying, as I spoke about briefly earlier, areas that can be this more native-heavy and also a little wild, or looser. I’m transitioning some areas to that kind of planting and management. And that is, in a way, making it easier than in areas where, say closer to the house in a more formal bed, where I’ve got a mix of native and non-native plants, it’s harder for me to come up with a strategy for those.

Because again, there might be a little flower bulb planting underneath where there might be tiny primulas that are going to come. Yeah. So I’m finding by devoting areas, like at the periphery of the property—coming in from the property line. I used to mow up to the property line on two sides, and I’ve backed up and I’ve come in and unmown those areas, and those have become my target areas for all these beautiful oak leaves that fall on the lawn.

Do you know what I’m saying? It’s like, can we create zones, even small zones, that we can manage a little looser?

Uli: Yeah. Well, and those more delicate plantings are a perfect place to take shredded leaves that fall on your site, and to mulch them and to enjoy that a little bit tidier aesthetic, and if you have the space, to allow the edges to be a little bit rougher or more wild.

I wanted to ask, how do you manage your woody debris?

Margaret: Yeah [laughter]. It’s a problem. I’m surrounded by woods, and so I have a deer fence around most of the place. And there is some opportunity right outside the fence at the perimeter of my property to have some brush piles and so forth, so I do that.

With large woody things, like if I lose a tree, I let the carcass lie unless it was right in the middle of the backyard by the door or something. And people kind of look agog when they see that, because I’ve got some carcasses here [laughter], some old friends who are lying on the ground now degrading into the soil and becoming part of the life. And that’s my thing. So I try to make brush piles that aren’t in prime area, where I’m looking at them everyday, because the nature of the garden right around the house doesn’t allow for that visually, to my eye. And I’m putting them at the perimeter, but I do have a couple.

And large takedowns, which I try never to take something down but rather make it a snag for years. And then eventually if it has to come down or it comes down itself, I try to leave the carcass lie. And that’s a different aesthetic, and not everyone would like that, but to me it’s important biomass that I want to have stay in the community. [Above, a birch snag with woodpecker holes at Margaret’s.]

Uli: Well I bring it up because it reminds me of two different approaches that I have. Well, one is the idea of using those, that woody, brushy debris a little bit more intentionally. You can make almost like a fence line with it.

Margaret: Yes.

Uli: If you sink in a couple of vertical posts and you can weave it in between or orient everything in the same direction so that it looks a little more visually pleasing. But those brush piles are also really critical habitat for mammals and small birds and other things and insects that I think also need to figure into… Anybody who manages a garden knows you’re inevitably going to have twigs and sticks and other things to deal with, and they can be treated similarly with that same kind of intention to benefit wildlife.

The other approach I wanted to bring up is one that I have had long conversations with, one of my former colleagues, Chris Roddick, whom I think you-

Margaret: Sure. Also formerly at Brooklyn Botanic Garden. Yes, an arborist.

Uli: And it’s about looking at how to prune trees to create microhabitats for fungi and for other sorts of things. And there’s this a movement within the larger arboriculture community to don’t just do flush cuts. If there’s a natural break, then leave that, because that has all these little nooks and crannies that are places for insects and for lichens and fungi and other things to come into place, and even mimicking natural breaks through what are called coronet cuts. So you’re using the chainsaw to rough it up and make it look jagged and natural. [Above, a coronet cut; Uli Lorimer photo.]

Margaret: Right. That’s what I do with my snags.

Uli: There’s lots of wonderful information about how to do that and so forth. For me, as my aesthetic has developed over the years, I would prefer to look at a snag or what looked like a broken branch than a flush cut.

Margaret: Yeah, no, I know what you mean. It looks artificial. Yeah.

Uli: Well, but it also, it means that humans have been there.

Margaret: Yes. Exactly. Evidence of human. I just want to ask you, I know you have a virtual event that I want to alert people to coming up in November, “The Need For Seed,” a symposium about the need for restoration to have a good supply of seed or regional seed sources of natives. But just to say that there’s lots of education, much of it virtual, available through Native Plant Trust. There are some great events coming up. [Above, the Hop Brook, area at Garden in the Woods; Native Plant Trust photo.]

Uli: Yeah. So the symposium is, we’re really excited to launch this. The registration is free for all the participants thanks to support from the U.S. Fish and Wildlife Service.

Margaret: That’s great.

Uli: And really what we’re doing is we’re, as an organization trying to step into, fill a really missing piece in the native plant material supply chain in the Northeast. And that is-

Margaret: So important.

Uli: They’re aren’t enough facilities to clean and store seed. And there’s a huge gap in the availability of genetically diverse, regionally appropriate, locally collected seed that not only feeds into restoration projects, but would also feed into retail consumer demand and growing plants from those seeds.

Margaret: Well, I’ll give the link to that and lots of other links with the transcript of the show. I’m so glad to talk about clean up and more. Now you’re going to get me going out and looking at my brush piles. So thank you, Uli; thanks for making time this morning.

Uli: You bet.


enter to win a regional native plant primer

I‘LL BUY A COPY of Uli Lorimer’s “The Northeast Native Plant Primer” or the Southeast or Midwest editions in the series for one lucky reader; your choice. All you have to do to enter is answer this question in the comments box  below:

Are you doing anything differently in your fall cleanup lately?

No answer, or feeling shy? Just say something like “count me in” and I will, but a reply is even better. I’ll pick a random winner after entries close at midnight Tuesday, November 8, 2022. Good luck to all.

(Disclosure: As an Amazon Associate I earn from qualifying purchases.)

prefer the podcast version of the show?

MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 13th year in March 2022. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the Oct. 31, 2022 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify or Stitcher (and browse my archive of podcasts here).

  1. Martha says:

    This episode was so timely! I’ve focused on adding in a lot of pollinator friendly perennials and want to keep that goodness going into winter prep!

  2. Karen Dowicz Haas says:

    I created a “hugelkultur” from a dead tree trunk and I will be leaving more of the garden leaves around it and in another area of my yard.

  3. Clara Burns-Trogdon says:

    I leave the leaf litter and the stems of my plants for the insects to overwinter. I used to cut them back but after listening to Margaret’s shows I leave them now.

  4. Lorraine King says:

    We have about 3 acres, so most of the leaves are mowed in place or blown onto the property border as a leaf-raised bed.

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