Star Thistle/Spotted Knapweed


#1

I moved to my present location 7 years ago. My burgeoning orchard had been corned for years. That, on a “mineral” soil type left the field, shall we say, deficient for most living things. Knapweed took over.

Multiple years of light discing of cover crops did some damage to the scourge, but it’s still there.

My current regimen of wood-chipping near trees and cover cropping/incorporating the alleyways seems to be improving the soil, but the Knapweed persists. I’m beginning a regimen of light wood-chipping the alleyways/incorporation with light discing.

My question, as Knapweed is known to thrive in substandard soil when/where other plants can’t survive, I am wondering if eventually, with improved soil fertility, other plants will be able to squeeze it out. My backup question… should I even care in a cider orchard? It seems that eventually the trees will live above the scourge.

Thanks!


#2

It’s a toughy. Maybe this would be of interest, or not:

http://www.mtbiocontrol.org/biocontrol-systems/spotted-knapweed/


#3

As you have noticed, knapweed is extremely persistant. I was told that my area was too moist for knapweed. Now we have it all along the creek bottoms. LOL I doubt that it would affect the orchard trees very much but it does spread easily far and wide by seed clinging to vehicles. It will take a long time comitment to try to keep it under control. Perhaps by fencing off a small tract for establishing and overwintering Knapweed Seedhead Beetles and frequent mowing or hand pulling to try to prevent it from going to seed. The seeds can rest in the ground for years awaiting the ground to be disturbed allowing them to germinate. Knapweed requires disturbed ground to germinate and grow but once established, competes easily with grass and other forbs.


#4

If you mow it a lot it will be more unhappy than the grasses which will be able to out-compete it since they bounce back faster from being mowed. In particular mowing right before flowering makes it the most unhappy, plus a couple times right after that to knock back the re-starts.

We don’t have that thistle here but we have Canada thistle. It is hard to get rid of, but 10+ years of weeding and it’s mostly gone.


#5

Folks seem to want to protect the bees…but want to kill dandelions, clover, star thistle, honeysuckle and the list goes on.

Honeybees aren’t native to the USA. But, unless you want to hand pollinate, you can’t grow a commercially viable monoculture orchard without them.


#6

I’m more than happy to have some star thistle. I’m not so happy to have a field dominated by it. My bees appreciate diversity in their foraging.