Probably yes,but it would be helpful to know which stumpkiller you used and how long ago you applied it (presumably just to the stump itself and not the surrounding soil?)

Thanks Bamboo. I don't know what was used, as it was done by a professional tree surgeon, but it was about 5-6 years ago. Applied only to the stump which was approx. 18" diam.

Well after all that time it should be fine - the biggest risk is from honey fungus growing off the stump rather than toxicity of the soil. Best to dig around a bit and remove what you can if its rotten already...