Sweet coneflower problem

Dave Robinson

I replanted 1/2 acre of natives after two complete growing seasons of spraying everything green that showed up. Lo and behold...the Sweet Coneflower that was one of the more villainous plants that caused me to start over after eight years is everywhere. It appears that either the seedbank from before was huge or the rhizomes remained dormant? Roundup resistant? Anyone else have this problem? Right now I'm hand pulling each plant..and there are thousands of them...if I can't get a handle on it I may have to start for the third time but then again I wouldn't know what to do about this stuff...wife not happy about the $1000+ in seeds so far and climbing...zone 5a. Very rich soil...when I removed them three years ago in the fall they were over seven feet tall...shaded out everything.

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dandy_line (Z3b N Cent Mn)

What is sweet coneflower? It sounds like it's a native.

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WoodsTea 6a MO(6a)

I assume Dave is talking about Rudbeckia submentosa. It's native to the Mississippi Valley and adjacent states, but perhaps he's in a different part of the country. Either that or it's just that it's too dominant in the mix. There's an elementary school in my neighborhood that has a patch of prairie that they seeded years ago and basically leave alone except for a late winter mowing, as a sort of outdoor classroom. In its early years it's been dominated by a particular yellow composite that I haven't made a positive ID on -- goldenaster or rosinweed or some such -- and looks pretty bad by this time of year. I am always thinking that they would do better to mow a second time later in the year, say in early May, which would give the late-emerging warm season grasses a competitive edge and balance things out a bit.

Dave, what natives have you planted that the coneflower is competing with?

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Dave Robinson

I am indeed talking about Rudbeckia Subtomentosa. It was a very small part of the seed mix i originally used from Prairie Moon (at their suggestion) in 2003. I'm attaching my latest seed mix to this comment. Note the absence of any goldenrods or rudbeckias...I'm very worried that this will again dominate the entire planting. Maybe I should plan on mowing the planting every year a couple times to keen the bad guys suppressed?


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WoodsTea 6a MO(6a)

It'd be interesting to hear what wisconsitom has to say about this, since he deals with large area restorations, unlike several of us regulars here that have small yards that we can more easily hand pick to maintain the right mix.

Part of it may be that certain plants can take several years before you see much top growth, because they are busy building root systems in case of drought. Baptisia is like that, as are a number of warm-season grasses. With time I think you will see your mixture change a bit. Unfortunately it could be quite a long time. Most of what I see in the list above aren't very tall species, so your Rudbeckia could continue to dominate for years (decades?) to come.

If I were you I wouldn't do another round of kill-and-reseed -- I think you could easily end up in the same situation and then you'd have restarted the clock on all the slower-growing plants that might compete with the Rudbeckia. I would think the best thing is either to pull or spot-kill the Rudbeckia as often as you can, especially as it starts to put on height.

The May mowing I mentioned above primarily helps things that do most of their growth after that. Big/little bluestem and Indian grass are good examples. My ideal meadow would be pretty grass-heavy, but maybe that's not what you're trying to do.

Is it just that there is too much of the Rudbeckia? Or are you, say, trying to keep your meadow below a certain height?

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texasranger2

My sister had these in her large corner lot and they took over just like you are describing, she renamed them RUDEbeckia. She has rich Kansas soil, the plants were giants and multiplied like rabbits after a couple years. She finally ended up hand pulling them all and ended up with a full pick up load of pulled plants piled high in the back of her truck which she had to drive to the dump because it was too much plant material for city pickup. The next year she weeded out all seedlings and finally got rid of them. She said they looked pretty in spring but got so big and were too aggressive. On top of that they looked terrible in summer when the heat and dry weather kicked in. I read a post here sometime back where a guy was dealing with them in a mixed planting, said the rudbeckia were threatening to take over the entire area at the expense of everything else.

Its native but definitely its a thug native, at least it is in good soil.

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wisconsitom(Zone 4/5)

Indeed, it is common for the plant matrix to change and evolve over the years, especially in the early going. for the most part, I agree with Woods Tea that it would be a mistake to set this back to zero again. You might be doing better than you think you are.

One of the common things I see happen is with regard to prairie grasses-big blue, Indian, switch. etc. The more you use fire, the more warm-season grasses you end up with. We've been so successful with this simple bit of strategy that I'm intending to diminish the use of or frequency of fire in some of our sites. I like the grasses-don't get me wrong-but I don't want just that.

Dave, I'd have to do my own research to learn whether or not R. subtomentosum has exhibited any herbicide resistance. Honestly not sure. I would though suggest taking a few deep breaths, seeing if maybe you don't like what's going on more than you think you do, and investigate slow management protocols that can help you up the species diversity....without starting over from scratch.

As long as we're on this topic-and I do admit, I'm taking it in a slightly different direction here-I'd like to recount two tales of plant succession: First, at one of our large stream restoration sites, which contains much "prairie" plantings...one of the engineers I work with was highly concerned about an explosion of red clover on the site. We get lots of that, along with bird'sfoot trefoil, vetch and other leguminous weed species. I told here-she is rather easily set off-to not worry about the red clover. As the prairie species take hole-all of which are taller than red clover-that species will lose the battle, and so it has gone. You can still dig around and find red clover, as well as the BFT, but neither are "problems" at this point, and their very future within this matrix is going to be limited.

Then the other thing: So, three springs back, we planted 6000 seedlings on land I own. The filed had been Roundup-ready corn, so no herbicide carryover effect whatsoever. After the trees were in, the filed just absolutely exploded in lesser ragweed. Well, it was a wet season and "lesser" ragweed was all head-high and taller. 20 solid acres of nothing but ragweed. A quick calculation told me there was simply nothing I could do about this, so that's what I did-nothing. In one year's time, that entire filed converted to perennial, native (albeit common and somewhat "invasive") species like giant Canada goldenrod, various asters, etc. Pretty amazing if you ask me, and all by doing nothing. That's not exactly your story, Dave, but it does serve to illustrate the enormous changes that can take place, even within a fairly tight timeframe.

+om

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Dave Robinson

thanks for the observations. after I "lost it" three years ago to Canada goldenrod and the SC I decided to reseed (after spraying for two years) with the shortest forbs i could find, lots of different sedges and tall grasses which due to the climate here develop VERY slowly. I'm near Lake Michigan and have cooler moist summers for the most part. Soil is VERY rich. I planned on being happy with the shorter plants and sedges which i figured would compete well with the larger indian grass and side oats grama. I attached a couple more pix showing the proliferation of the SC. This was two weeks ago...it is literally blanketed with yellow now.

If I were to mow (with a weedwhacker) twice a year, first time when the plants hit two feet and knock them back to about one foot, then the second time when they hit three feet and knock them back to two feet might this not give the shorter plants time to compete with the evil SC?


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WoodsTea 6a MO(6a)

Gotta say that looks pretty nice to me. Love that prairie dock! I'd be tempted to let it go as is and see how it plays out over the next few years. Maybe add something like Liatris spicata for color contrast...

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Dave Robinson

YES..it looks great for now! BUT I've seen this movie before...during the long winter months here i start hundreds of prairie plants in my basement in "conetainers". Then in spring after burning and it starts greening up I go out and zap numerous dinner plate sized areas with roundup and plant the seedlings in early summer...worked great a few years ago...until.....(que up the Jaws soundtrack) SC and Canada Goldenrod completely took over...

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wisconsitom(Zone 4/5)

Well, that Solidago is indeed a rampant grower, no use denying it. I'm not sure of an exact strategy for the Rudbeckia but your mowing idea makes sense to me, if indeed you would like to reduce its prevalence in the planting. But given the presence of all that C. goldenrod, you may well have to start over if you really wish to get that under control. Not at all saying this is what I'd do-I tend to try and work with the natural flow of things a bit more-when I can-but if it is really bothering you that much, then yes, it's probably start-over time. One thing about goldenrods and indeed, all asters for that matter-they aren't too terribly distinctive prior to bloom time, so it can be quite a chore to try and ID what you have in say, early summer. But if you would happen to get adept at this, you could simply spot-spray with glyphosate and try to reduce the clumps of C. goldenrod that way, and maybe for the yellow cone too.

+oM

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WoodsTea 6a MO(6a)

I wonder if ultimately you will need to bring in taller species to compete with these two. I notice some grasses in your list like sideoats grama and little bluestem that are relatively short and compete much better on drier, less fertile sites. Switchgrass (and bluejoint?) would seem like a natural fit for your site, but taller than what you seem to be wanting.

If your site would naturally be a forest, or a tallgrass prairie/savannah, then I wonder whether trying to keep it short will inevitably require considerable annual effort.


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Dave Robinson

all good comments thanks.. I stuck with shorter plants overall (I was NOT expecting the SC to be there) as that is the look i'm after. My simple plan for the SC is to pull as many as i can. Then spot spray next year and after the proper amount of time has passed, plant natives that I start inside (and harden off of course) in the empty areas. The battle with the SC has been going on for several years now...by starting over I had hoped to have a clean slate but clearly that isn't happening...if i had to guess this would have been a hardwood forest at one time...very rich soil with clay substrate...

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