Do not want to dig up Dahlias, but what about the soil?
Hi, Last year you gave me excellent advice to amend very poor clay soil we have up on Cooper Mt, in Beaverton. I used red clover after amending with compost etc.Planted dahlias and are beautiful! However this year I do not want to dig up my Dahlias. If I plant clover I can't rota till it up. So how do I amend the soil with my Dahlias in the ground? Please advise, thank you so much! Cathy Smiley
https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/fs304.pdf Thanks for your question about dahlias, cover crops and soil maintenance! It's really impossible to have a cover crop that needs to be removed with a rototiller, and expect bulbs to survive. Since the experts recommend covering dahlias with 6" of soil, your tiller blade will just shred them if they're left in the soil.
In warm climates (where there's no risk of the tubers freezing), tubers can safely be left in the ground but I'm not sure what your soil's temperature gets down to. (Cooper's Mountain sounds cold!)
Perhaps this is the advise you got last year, but it's the OSU publication on dahlias And here's the OSU publication on cover crops, but it recommends the same 6" tilling or raking of top soil.
If you don't mind jeopardizing your tubers (with either frost or rototilling them), you just might need to have a backup plan, like starting them from seed next spring, having harvested the seeds from this year's flowers.