To thistle or not to thistle...

agkistrodon(6/7)

Hello...this is a "what would you do ?" question and I'd appreciate ANY input. I moved to this property about 3 yrs ago. It is a combination of woodland and grassy/scrub. I've pretty much left the woodland alone but added some VA bluebells which have done very well. I wanted to take some of the grassy areas back and plant them w/full sun natives and native grasses for birds and insects. When we first arrived there were Canadian thistles everywhere and they were swarming w/swallowtails...I thought it would be best if I got rid of all the thistles because of their invasive habits and replace them w/a native alternative....long story shorter...I got rid of a lot of them and the swallowtails went w/them! Now, I am rethinking...maybe I should let the thistle recolonize in patches? Can you control thistle? Is thistle so bad? I am starting some full sun natives (Asclepias, Liatris, Echinacea etcetc) from seed but it's obviously going to be 5 yrs or so before the natives provide what the thistle can provide overnight! It's not as if the thistle is trying to invade a pristine native habitat...the habitat is disturbed and artificial to begin with. What do you think?

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lycopus(z5 NY)

The Liatris may take a bit longer to flower from seed but the milkweed and purple coneflower should flower in the second year and possibly even the first year. There are also native thistles that could be used as a replacement. Cirsium discolor looks pretty much like C. arvense without the spreading habit. Cirsium muticum is another but needs a moist habitat. Also if you like black swallowtails you might consider planting native members of the parsley family (e.g. Zizia aurea), or for giant swallowtail prickly ash is the primary host plant in the north. Tiger swallowtails use Prunus spp., birch, tulip tree or sassafras as host plants.

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agkistrodon(6/7)

Thank-you for your input! We have zebra swallowtails that go for the paw paws and spicebush swallowtails that go for the spicebushes and a scattering of the tiger swallowtails that seem ok w/the dogbane and another plant whose name escapes me but there were literally clouds of tigers when the thistle was everywhere....hoping to bring them back so I will get some Zizia seeds and try some C. discolor. We are overrun w/tulip poplars (my 8 yr old calls them tulip populars :) and I have a weakness for sassafras...though they don't seem to live very long around here. I will carry on the war against C. arvense...I shall not give in to tiger swallowtail temptation!

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agkistrodon(6/7)

Another ? What is the difference between Zizia aurea and Zizia aptera? Did you suggest aurea because of the swallowtails? Just curious because they seem to occupy similar habitats...I am unfamiliar w/them. I am making a list for seeds to fall sow!

Thank-you!

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lycopus(z5 NY)

Zizia aptera has heart shaped leaves and might work better in drier soil. The reason Z. aurea came to mind is that it is the more common of the two around here. Both can support caterpillars.

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wisconsitom(Zone 4/5)

Excellent recommendations by Lycopus, to which I'd jump in to say yes, get rid of the noxious weeds that are "Canada" thistles. You've laid out the parameters of the situation very well, yet despite the fact this is not some prisitine plant community, C. arvense is rightly placed on noxious weed lists across the nation. And it's no picnic eradicating it either, though one can eventually succeed, as you have partially done.

Work with the native suggestions. In time, you'll have the butterflys back while also having a much more interesting plant community in place!

+oM

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