You could have blackberry plantlets from the root pieces (along with seeds from fallen fruit left in the soil sprouting more blackberries).

If you're willing to keep an eye on this soil, vigilantly removing any sprouts, it can be used.

Screening the soil might help if there's a lot of root...getting some of the stronger roots out of the soil. Some chicken wire on a frame (or something similar) screening it into a barrel/wheel barrel/tarp/etc.

If the berries grew extremely well in this patch the soil itself might be a bit low in pH, too...so that might be a concern adding it to a garden in large amounts unless it could help the pH of the soil you're applying it to.

This post was edited by nc-crn on Wed, Jun 12, 13 at 17:45

Those soils (weedy for 20-30 years) are the best, leaves and debris accumulated for a long time and the food web is perfect. Brambles in the garden are horrible and survive repeated cardboarding. high risk high reward...