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Day lilies can be divided and moved, even when blooming, like these under cloudy skies this morning, July 8, 2013. Photo:  Martha Foley
Day lilies can be divided and moved, even when blooming, like these under cloudy skies this morning, July 8, 2013. Photo: Martha Foley

When the garden gets overgrown

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With continually rainy weather over the last few weeks, and more in the forecast, there'll be no stopping the garden from growing. But, there may be something to be done about over-growing: Cooperative Extension horticulturist Amy Ivy talks with Martha Foley about exerting some judicious control over the lush life in the perennial beds.

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MF: It’s a jungle out there, as Todd Moe said.

AI: It definitely is. Oh my goodness.

MF: We talked a little bit about this last week, but it’s certainly worth returning to. First of all, everything in my perennial garden is looking great. Right? It looks great, but it all looks about twice as big as it should.

AI: Yes, and it looks better from far away, but when I get close, it kind of makes me cringe.

MF: So why does it make you cringe?

AI: Well, there’s just so much stuff that’s lying on top of other things, and it’s just a jungle in there. There’s so many things that have volunteered that are just going crazy, and there’s some weeds that I blinked and they grew two feet. So from a distance it looks nice and full and lush, and then up close I realize it needs some real attention.

MF: Well, what’s happening. I have a lot of lilies, I have Asian iris-type things, I have day lilies, and all of their leaves are so big and they’re just flopping on each other and flopping on everything that’s nearby. Can I just cut some of those extra leaves off, and how much is too much?

AI: It’s a judgment call. Once something has finished blooming, then you can be a lot more aggressive with your cutting. Most of the day lilies are at their peak now. Actually, that’s the one plant that can be removed and divided while it’s in bloom; it’s just so resilient. But anything else I’d hold off on until just after blooming. The earlier things you could definitely do. If you have any Iris, now is a great time to divide it. I would dig the whole thing right up.

MF: And throw it out (laughs).

AI: No, don’t throw it out (laughs). Dig it up, trim it down, and divide it would be great. I’ve got some things that are finished. I’ve got feverfew, which I really like a lot, as a filler plant. But it’s done now, so I can just yank that out, because it keeps volunteering from seed. And I have Johnny Jump-ups that I kind of let fill in the gaps, but then I blink and suddenly they’ve taken over the gaps. And I can just yank those up, because they come back almost like a weed as well.

So there are a lot of things like that, I want to clear up the debris. I just pulled up all the forget-me-nots, which I finally got established. I’ve been wanting to get some, and they were great this spring, but now they were just big old gnarly things. So those I could yank right out, and that really helps to open things up and let things breathe a bit.

MF: You’re talking about dividing day lilies, and I think I’m going to do that…and also iris. I’m concerned about phlox, because it gets this moldy stuff, this powdery mildew. And one year when it was wet I had to cut it all down. I’m wondering now if I thin it out, will that prevent that terrible stuff?

AI: It will prevent some. With all the humidity – powdery mildew likes humid weather more than actual rain—and we’ve had both, so I don’t quite know. When it’s really rainy, actually, powdery mildew is actually inhibited. But who knows, it will probably turn to hot and steamy before to long, anyway. I think we’re kind of doomed. But yes, thinning out phlox is actually a recommended practice actually, because it comes up so straight. All the shoots come up like a forest of little trees, just about. So you can go in there  — the earlier the better, but I wouldn’t hesitate to do it now – and cut them down as low as you can, all the way to the ground. Select, and thin out that forest of phlox shoots. And that will at least help.

Anything to promote air circulation, so that we do get a breeze, it could help dry those leaves off. Air movement is a good thing in the garden, so anything you can do like that to thin things out. I’m going to cut down my baptisia pretty soon, too. It’s all through and the seed pods on it get so heavy and the whole thing just lies flat, especially in wet weather like this.        

MF: Well that’s not good.

AI: No, it’s not because it just totally covers its neighbors. A couple years ago, I just couldn’t stand it and I cut it down. I figured, I don’t even care what happens to this thing, I was so mad at it. And it loved it, it did really great; it put out new growth, it was much more contained, it was smaller but beautiful. So I’m going to keep doing things like that, I keep saying I will. I was weeding this weekend, so I can’t get it all done on a weekend.

MF: Well the other thing is that the mosquitoes are terrible right about now.  Mosquitoes are really terrible in my yard, let me say that. And I’ve been mowing more, actually, and watching for little pools of water – the cat dish or something like that—but there is so much water everywhere and every time I go out in the garden I’m attacked by these angry bugs.

AI: Yes. Knock on wood, they haven’t been that bad at our house, but we’re a little bit more open in general. We aren’t too mosquito-prone, but other people just live in mosquito habitats. With this weather, your cat dish is really a drop in the bucket. There are so many areas and puddles that you can’t really fight it this year. You just protect yourself and hopefully the breeze helps. The breeze helps a lot. Particularly irksome to me is this heavy air that is just sitting there. I think that if the air was blowing around a bit, it would be more tolerable.

MF: I’m going to ask you about a couple vigorous plants. We’ve talked a bit about day lilies you can divide and move around now, but I have an extremely vigorous virginiana clamatis, and I’m not sure what to do with it. It really is the vine that’s eating my flower garden and my black raspberry patch.

AI: Yeah, it will. Of all the clamatis group, that one –I think it’s also called Sweet Autumn – is terribly aggressive. You really want to be careful about where you plant that one because it grows, would you say, maybe 20 feet in a year?

MF: Oh, easy. Yes, oh yeah.

AI: But it’s fragrant, it’s lovely.

MF: Well, mine is not fragrant, is really the irony here. I thought it was, but not this particular individual.

AI: Anyway, you or a listener might have been tempted by description. Whenever it says anything about vigorous growth or anything, what they really mean is AGGRESSIVE, WATCH OUT. The catalogs use euphemisms a lot to describe their plants. Yeah, that one, you really want to be careful where you put it. Don’t plant it at all, or plant it where it can grow 20 feet, because you can’t fight it. A plant that wants to be that big needs that room.

MF: So can I…how do I get rid of it then? I don’t know what to do about it.

AI: You can cut it down, and then you’d have to dig the roots out if you really don’t want it anymore. Dig up the roots because it’s so vigorous, cutting it down will probably invigorate it more. Try that, and there are so many other clamatis that are so much better behaved, that would be a better choice. Just make sure you get the kind that bloom on the current year’s growth, so that if they do die back over the winter they can still re-grow from their roots.

MF: As soon as I get all my black raspberries picked from underneath this aggressive vine, maybe I’ll just dig it up and see what happens.

AI: There are times –gardeners just have such soft hearts they hate to get rid of things—but there are times where some plants just don’t belong in your yard anymore. I tend to be pretty ruthless that way. I know some people just want to let everything live, but I think it’s okay to remove some things if they’re not behaving themselves.

MF: Well thanks for the pep talk (laughs) and we’ll talk next week.

Amy Ivy is horticulturist with the Cornell Cooperative Extension Service of Clinton and Essex Counties.

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