Last year, I dug up two beds for dahlias. In one, I put all kinds of potted soil from my geraniums etc. In the other I left it alone, but did note there was a lot of clay and sand mixed there from the building site. In the bed with the potting soil added, the dahlias were huge. In the other bed, the dahlias were much smaller.

Do I recommend amending? Yes. This fall, I have already dug up and stored my dahlia tubers, but I have also added compost, and more potted mix to the bed that did not perform so well. I have screened out the clay clumps as well, so now have a nice blend of compost, sand, potting soil, and triple mix. We'll see how they do next year.

Looking forward to MAMMOTH dahlias next year. LOL

Jroot Thanks so much for your reply! O.K. I have all the ingredients that you mentioned and will amend the soil in the sites I have chosen. Now I'll order some Dahlia tubers for a new year of surprises! Pat