ANOTHER GARDEN SEASON is complete, and we’ve just passed the end of another year of the radio show and podcast, too, which I create each week to share with you, of course. But there is also a selfish factor at work, because I get to ask experts I admire the questions I need the answers to.

That’s today’s topic: top tips I got from 2019’s most popular interviews—like whether to use black or clear plastic to smother weeds, or how to diagnose the presence of dreaded invasive Asian jumping worms. And on a brighter note: when exactly to cut those peonies to have the longest-lasting blooms in a vase, and how to get maximum performance out of our familiar annual flowers.

Read along as you listen to the bonus show from the week of January 6, 2020 of my public-radio program and podcast using the player below. You can subscribe to all future editions on iTunes or Spotify or Stitcher (and browse my archive of podcasts here).

So: On to the tips!

flower power: top performance from annuals

FROM AN ORGANIC flower farmer-florist neighbor of mine in 2019, I got insights about coaxing maximum results from familiar annuals like zinnias, celosias, cosmos, gomphrena, rudbeckias, marigolds—the ones that you can pretty easily start from seed yourself.

Jenny Elliott of Tiny Hearts Farm in Copake, New York, is a farmer-florist who grows flowers organically, both for the wholesale market, for subscribers to her weekly flower CSA, and also for events, including weddings that she designs.

Her flower farm is like a giant cutting garden, but since she’s operating a business she has to have inventory of each crop over the longest possible season–meaning she doesn’t just sow once in spring, it turns out. She makes successions. Listen in to key parts of our early spring conversation now (the whole archived program with Jenny is at this link, to listen in full). Highlights:

Margaret: Now, again, in your “cutting garden,” 25 acres of it-

Jenny: [Laughter.]

Margaret: …you’ve got to have stuff, a succession of things. I’m assuming that just because you’re starting some of these things now or soonish to plant out in May in our Zone 5B, doesn’t mean you expect those same seedlings to be perfect and still producing flowers in August and September. Are you doing succession plantings of these things or what?

Jenny: Yes, we’re doing successions. Depends on the plant, right? We do four successions a year of zinnias.

Margaret: Wow.

Jenny: Yes, and Celosia. I think cosmos gets five.

Margaret: Wow.

Jenny: Yes. Just because, when it’s a cutting garden, too, you want top-quality flowers every time you cut, right? We’ll just ditch an old planting just because it’s not so good anymore, and move on to the fresh planting. Even though it might still be producing flowers, they’re not that great anymore. Keep having fresh plantings, and you keep getting really nice flowers all season long.

Then, there’s other things. Sunflowers, we plant every two weeks. Then, there’s a few things that we only have to do twice a year, so I do an early spring planting of gomphrena, and then we’ll plant out more in July. That gets us through the fall with a nice fresh crop of that. Strawflower, the rudbeckias we do twice a year, scabiosa. Yes, a lot of things. Then, there’s some things that you could succession plant all year long, but I kind of get bored of them, or things I don’t want to see again until the fall.

Margaret: Right. Right, right.

Jenny: You know what I mean?

Margaret: Sure.

Jenny: Calendula is one. Yes, we could grow it all year, but it’s … The oranges and yellows, I kind of want to see that yellow in the spring and then the orange and yellow again in the fall, but I have enough other orange and yellow in the summer that I don’t want it.

LISTENING TO JENNY, I finally got it: That sowing annual flowers once–for spring planting–isn’t going to get you through the entire possible season of maximum blooms and bouquets spring to fall (any more than sowing lettuce once does).

And I got another big tip from her, about the step we all too often skip when growing from seed: Pinching. Here’s what we discussed, in some clips from the original show:

Margaret: With some of the ones that we’ve talked about, do they require any other treatment like pinching or anything, or are these all things that just sort of you let go to their natural inclination?

Jenny: Gosh. I’m trying to think of anything I don’t pinch.

Margaret: Oh, good. O.K., so explain that to us, because, of course, a lot of us mere gardeners over here don’t do that. We set them out and we … You know what I mean? Tell us about that.

Jenny: Yes. Don’t get me wrong. I start every year with the intention to pinch everything, and of course, I don’t get to everything and they do fine. But, yes, we pinch everything when it’s … General rule, I would say when it’s about 4 inches high, we pinch it down to about three sets of leaves. All the zinnias … I guess certain celosias, I don’t pinch, like the brain celosias. They won’t form that big center flower if you pinch them.

Cosmos does much better pinched. Gosh, just about everything. Yes, so you pinch it down and it seems really harsh and scary and like you’re killing your plant. All that it does it lets you get more taller flowers.

Margaret: Huh.

Jenny: You’re really doing a good thing.

GOT THAT, EVERYONE? Successions of almost all your favorite annuals–lots of them–and pinch, pinch, pinch!

the update on asian jumping worms

LET’S MOVE ON to a less appealing topic: so-called crazy worms or Asian jumping worms, several invasive earthworm species that are spreading alarmingly and degrading soil and natural habitats. Many of you have asked specifically, “How can I stop them?” and unfortunately, researchers do not have an answer, at least not yet.

For an update on directions in research I called Brad Herrick of University of Wisconsin-Madison Arboretum, where the staff first noticed the destructive effects of Asian jumping worms in 2013 and has been studying them since.

I asked Brad how to tell if you have the worms, which are increasingly widening their territory in the Eastern US, the Midwest, and have even been identified in Oregon.

What are the telltale signs of these worms versus familiar earthworms who do not degrade the soil so dangerously? Listen in to clips of our July conversation (or the entire show at this link instead), around the time these invasive species reach maturity:

Margaret: now that you’ve been seeing them since 2013, if people ask you, other than doing DNA analysis or whatever-

Brad: Yes, right.

Margaret: Like what do you say the telltale signs of these worms versus the other earthworms that we talked about?

Brad: Yes, so a couple of things, and it somewhat depends on what time of year you’re looking for them.

Margaret: Yes.

Brad: But the first thing that you can see any time of year is this specific soil signature. And that is these Asian earthworms produce a very coffee-like, or coffee ground-like that signature in the soil, really loose, granular soil that’s actually made up of their castings, their excrement. And so they create this layer of really loose soil, really granular soil, which all earthworms produce castings, but most earthworms produce little … kind of little casting hills or little bumps, kind of  sporadic around the landscape. Where jumping worms just create kind of a homogenized, uniform look to it. That’s one thing that you can see in the winter, if you get a snow melt, you can … As far as we know that’s a permanent change to the soil. So that’s one thing.

And then as they mature, so in Wisconsin they’re almost … we’re almost seeing mature adults [in July]. So Amynthas, or jumping worms, generally if you look … if you have one and you look towards the head, even if you can’t figure out which end is up, there’s a white ring around one of the ends.

Margaret: Right.

Brad: That goes all the way around the body, and that’s called the clitellum, and that’s where they produce cocoons that are the new offspring. It’s kind of the reproductive center of the earthworm. And all earthworms have one, but most earthworms, their clitellum is kind of the same color as the rest of the body and it’s raised, and it doesn’t go all the way around. If you turn the earthworm over, it’s kind of like a saddle where it doesn’t connect underneath.

Margaret: Right, not a band.

Brad: Not a band, right. The jumping worms all have a band and it’s kind of a milky-white band when they’re fully mature adults. That’s a telltale sign. There’s no other earthworm that isn’t a jumping worm that has that kind of structure.

And then lastly, just their behavior. They’re called snake worm or jumping worm for a reason. They can be very erratic, very … They’re not aggressive, they just don’t like being handled, and they will flop around and they’ll wiggle away. They’ll even try and drop part of their tail, the last several segments, to escape being handled roughly, where other earthworms are kind of wiggly, but they’re not actively flopping around and trying to get away from you.

So … and I guess maybe more thing to mention is that early in the spring, April, May, if you’re seeing fully formed earthworms, large earthworms, those won’t be likely, won’t be jumping worms because jumping worms are an annual species, and so under normal climate conditions they’re going to be hatching from cocoons. They’ll be really tiny in the spring, and won’t be full size until the middle of the summer.

Margaret: Right.

Brad: Or end of the summer even. So any large earthworm you’re seeing in April, May is some other species that is not a jumping worm.

WANT TO KNOW MORE? Listen to the rest of my talk with Brad, who also gives a recipe for what’s called a mustard pour that can be used as a test on a small area during the worms’ active season to confirm their presence, along with lots of links for more information.

weed control: solarization and tarping

FROM UNWANTED WORMS…to unwanted weeds, and specifically non-toxic tactics for their control. I called Dr. Sonja Birthisel, who had just completed her PhD at the University of Maine in late 2018, and focused her research there on helping farmers by studying practical solutions for issues posed by climate change, weed management and more.

That included the subject of soil solarization that many of us gardeners use, too, in the name of weed suppression. She shared insights from her research that we can all benefit from, including the subject of the effects of clear versus black plastic—and how using black material isn’t really solarizing, but something slightly different.

What is solarization and what has it been used for, and where, historically, I asked? Some key highlights from the show (which is here in its entirety if you prefer):

Sonja: Soil solarization is the practice of covering moistened soil with clear plastic for a period of weeks, and this creates a local greenhouse effect. Solar energy heats up the water molecules in the soil. That heat stays trapped under the plastic. If conditions are suitable, you get temperatures hot enough to kill pests, including plant pathogens and weeds. This has been used most extensively in parts of the world that are much hotter and sunnier than Maine. I’m thinking of Israel and Southern California. There’s been work on this done in Georgia, but not in Maine as much.

Margaret: O.K. You said a couple of things in that short description. “Moistened soils,” you said, and you said “clear plastic.” Let’s dig into those a little bit. Moistened soil because the sun will heat up the water molecules, so this isn’t so good on dry soil?

Sonja: Yes. The moisture does a couple of things. Moisture helps conduct the heat in the soil profile. If your soil is moist, so around field capacity not super water-logged, that will allow that solar energy to travel to deeper layers of the soil so you’ll get more benefit from the practice at more depth.

Margaret: O.K.

Sonja: That’s kind of the biggest physics reasons. Then also, if we’re thinking about this for weed management, it can help putting seeds into a more active life phase, maybe encouraging them to germinate. Then if you germinate under that plastic or start to germinate and it’s unsuitably hot actually, well, then that seedling is toast. It can improve weed management in that scenario.

Margaret: That seedling we’re talking is in the seedbed of the underlying soil, unwanted things, not the precious seed we just planted as farmers or gardeners?

Sonja: Correct. Hopefully our garden weeds, yes.

Margaret: Right. The other thing you said a little bit earlier is you said “clear plastic.” I was especially fascinated because I’ve been gardening a very long time, writing about it a very long time, and I thought I was an advanced intermediate. Not a super expert, but an advanced intermediate. I’ve interviewed a lot of super experts over the years, and no one had ever really said to me that using black plastic or a blackout kind of a cloth or fabric is not technically solarization, that it’s called something else entirely. Tell us about clear plastic versus some other substance.

Sonja: Clear plastic does actually get hotter underneath than black plastic. Both of these practices back in the ’70s and ’80s were considered solarization, but since then, the terminology has changed. Now we call solarization clear plastic or we call clear plastic solarization, and then using black plastic for similar purposes is called either tarping or occultation. Those are the two words I hear most often.

Margaret: Occult like the occult?

Sonja: Exactly, yes. Our word for the occult comes from the word for black. Occultation-

Margaret: I love it. [Laughter.]

Sonja: … is using black material, yes.

Margaret: Oh, I’m going to feel so sophisticated now knowing that. Thank you.

Sonja: You are already very sophisticated, but here’s just one more tool for your toolbox there.

Margaret: Yes, I love that. When you say hotter under the clear, how much hotter? I mean I know you can’t give me an exact reading probably, but is there sort of a rough range?

Sonja: Well, I probably have some exact numbers somewhere near at hand, but at least 5 degrees Fahrenheit hotter is what I was measuring in my experiment here in Maine, and that temperature difference can depend on where you are in the world for sure.

MORE PARTICULARS of how and when to solarize or tarp; the reminder to irrigate the bed first and how long it will take to get results, are in the archived original show with Sonja.

from ken druse: make a nursery bed

NO RECAP SHOW of any recent year of the program would be complete without the voice my friend Ken Druse, who visits about once each month to talk, and laugh, and help answer your Urgent Garden Questions. One such inquiry addressed to us by a listener named Kyle asked advice for planning a garden from the very beginning. Well, when Ken and I began discussing possible answers, the subject quickly mutated to the things we wish we’d included in our places right from the start, and that every gardener should make room for whatever stage his or her garden is at.  (This means you.)

Must-have elements like lots of well-placed outdoor faucets and electrical outlets, views from indoors (whether to accentuate the positive or eradicate the negative), and more – including one thing Ken did first of all: Make a nursery bed. Here’s more on that (from this past show should you wish to listen to it in its entirety):

Ken: Well, when we first came here, the first thing we did in the sunniest part, and it’s not very sunny here, was make a nursery bed. We could buy plants for what we could afford, often small trees even, and plant them, and then figure out where we wanted them. By the time we had figured some of that stuff out, we could shop in our own nursery bed. Because you could move almost anything.

The things were not tiny anymore. Things like roses or climbing roses had become plants, and trees were flowering. I would start a nursery. Ours is long gone, that nursery bed. I still have what I call splinter nurseries around the property. They’re pretty. They’re a couple of plants that I intend to use somewhere if I can figure it out. I want to get some meat on them. Especially when you buy a 7-inch tree [laughter], which we did a lot.

Margaret: When we were young, we were young once, Ken, we bought 7-inch trees.

Ken: Younger. [Laughter.]

Margaret: We believed in things like that. Yes. You’re absolutely right, and this gets back to Kyle’s question. I loved the punchline of his question, about what to budget on and where to splurge, what to budget and what to splurge on. There’s a big difference between a small woody plant especially, and then a “landscape size,” field-dug, ball-and-burlap, whatever. It may be only a few years of difference in the thing’s life, but the price difference is phenomenal.

You can have the very special things if maybe you grew them on yourself, you’re saying, in this little nursery.

Ken: Well, time is money and there might be something you’ve dreamed about. Certainly, for me there is, something I’ve always wanted to grow X. Or, this is going to be the big ticket item, one special tree that’s going to be a specimen. Even though people should have patience, and don’t ever think it’s too late, but maybe you want to buy a 20-year-old tree…

In that first nursery bed, the tallest plants, the trees, went on the north end of the bed. It was just a rectangular bed probably 25 by 30 or 40 feet. It was just with rows. The trees went on the north so they wouldn’t shade the other plants. Also, I don’t think I had a shade nursery in the beginning, but later on I did. Maybe a nursery bed in the sun and another nursery bed in the shade. It sounds ridiculous, but it was wonderful. Then three or four years later, they were empty.

Margaret: Well, and another thing you can do with it is when you have certain types of plants that self-sow and give you baby plants, but they do it often in the cracks in the driveway or in between paving stones or places you don’t want them. Rather than discarding them, you can accumulate them for use later when you start the next bed or whatever. I like to do that as well.

Frankly, I never made … I wasn’t smart enough to make a separate bed, but I do use a bed in my raised-bed vegetable garden as my “nursery.” You can activate one of your vegetable garden beds for this purpose.

SO GO AHEAD: Find a spot, even a small spot, and start a nursery.

when to cut peonies for longest-lasting blooms

OK, TIME FOR ONE LAST TIP, to get us dreaming about next spring and peony time. Jeff Jabco of Scott Arboretum at Swarthmore College in Pennsylvania is peony-mad, and an officer of the mid-Atlantic Peony Society, and in a June conversation he gave me growing advice and also this: when to cut flowers and prepare them to be longest-lasting in a vase .. an answer that surprised me. Here’s that clip, or you can listen to the whole past show (and actually that’s my neighbor-flower farmer Jenny, who was in the first clip in this recap edition, with a harvest of some of her many peonies, above):

Margaret: I wanted to ask you about, if we go back to the floral kinds or the lactifloras, if we want to use them as cut flowers, say we have a few that we want to put in a cutting-garden area, what’s the best time and way to cut them that makes them last? What’s the protocol there?

Jeff: Oh, O.K., great topic—and actually our local peony society, the mid-Atlantic Peony Society just had our last official spring gathering the other night, a members’ garden tour, and we had a peony judging. So, because we are at the end of the season we were telling people that if you want to enter some flowers into the judging, what you do is, when the flower bud starts to show color, so you’re going to see the petals there but it’s not open yet, just lightly squeeze it with your two fingers, and if it feels like a marshmallow—you know, the large campfire marshmallows, you make some S’mores out of-

Margaret: Yes.

Jeff: …if it feels like that, that is the stage where you cut the stem, O.K.? So you cut it off at the length that you would want, and then you wrap it up in newspaper. You just roll it up in newspaper and put it in the refrigerator. Just dry, like that.

Margaret: Dry newspaper. Oh.

Jeff: And then… Dry newspaper. Yup. And put it in the refrigerator, and then, you can leave it in there for days. You can leave it in there for a couple of weeks, and then you take it out, recut the stem just a little bit from the bottom, you cut an inch or two from the bottom, put it in water and then within one to two days it will be open fully for you.

Margaret: And this is the trick that the cut flower growers… Because they can’t afford for their whole crop to suddenly, if 90 degrees are coming, right? Or, you know-

Jeff: Right. Right.

Margaret: … they can’t afford to have a wholesale loss. So this is what they do, I think.

Jeff: And if you order peonies by mail, that’s what they’re doing. They’re cutting them at that stage and shipping them to you, telling you, “Oh, when you get them, just cut the stem and just put it in water and in a day or two they’ll be blooming.” Or, to have all these peonies for June weddings, you know, not everyone’s growing these in the far North, so they pick them earlier, they keep them, wrap them up, keep them in their coolers, and then they just take them out a couple of days before and they’re all set.

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for making the podcast possible

THANKS FOR JOINING me for a look back at a year of learning, and happy new year (and new decade!) wishes to all of you. May you have the best  year ever, and don’t forget to figure in plenty of time to just slow down and watch. And of course to keep listening!

Thanks to all of you for your support of the show in 2019, and don’t forget to say thanks to the smallest NPR station in the nation, Robin Hood Radio in beautiful Sharon, Connecticut, where my beloved neighbors Marshall Miles and Jill Goodman make it possible for me to produce it and share the weekly segments with you. You can thank them with a tax-deductible gift at robinhoodradio.com/donate. Happy New Year!

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 10th year in March 2019. In 2016, the show won three silver medals for excellence from the Garden Writers Association. 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 bonus show from the week of January 6, 2020 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).