Corydalis incisa is a nightmare- incredibly invasive, and can form a carpet of weeds that choke out any native or precious plants around ...Read Moreit.
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I spent another 6 weeks,from mid-March to 1st week of May, hand-pulling masses of this plant that invaded the stream bottom down the hill, 70 yards from where the first plant invaded 5 years ago.
If you have this plant, you must remove it in early spring, before the seed heads ripen and explosively spread seeds a meter in all directions. It is biannual, so if you don't dig or pull out the other hundreds of little baby plants that grow from tiny bulbs this season, they will become the big, vigorous purple-flowering plants that can invade your property.
1. Make sure to get the roots, which can remain as a fleshy-colored V-shape. If you don't get the whole plant, it will re-grow, shorter and wider and still flower and develop seed heads. I use a curved Japanese spike tool on a handle to get to the roots. This narrow point is also good when extracting single plants among the irises or ferns- get the point under the weed and pull straight up.
2. If they are growing on a hill, pull the plant out from below, upwards, as the root most likely started upbove the plant.
3. If you can't pull all before the seed heads set, hack them down to buy you some time. Then you must still pull them soon. I haven't tried the blowtorch mentioned elsewhere. That might torch those little bulbs, if no precious plants are in the way.
* I studied the hill that was inundated with the plants last year, where I spent days on my knees pulling up the mature plants, and there were only a couple of plants this year vs hundreds. I am pleased that, if you can get the plants out of there, you can break the cycle of seeding. Good luck to you.
We found it in one of our garden beds in DC two years ago, and it spread very quickly. We've managed to weed it all out, and have to be diligent about pulling it out every spring.
There are corydalis species that are native to the US. Plant one of those instead.
Corydalis incisa is a nightmare- incredibly invasive, and can form a carpet of weeds that choke out any native or precious plants around ...Read More
This plant is considered invasive and a threat to native species in the US. Please don't plant it in your garden. Here's a link to the so...Read More