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It depends on what, in particular and also on particular soil pH, etc. as to the extent of the effect. Foilage on bulbs, in particular, are likely to show signs...it's not so strong and effect as to be deadly to virtually any plant, but in general, a comparative specie outside the influence of the walnut will typically show better development than one within that influence. I'd not use it in veggie gardens simply as a precaution against poor germination, etc., not that I'd be concerned w/ human toxicity, etc. I also made the recommendation in context of the OP in this thread asking about using fresh sawdust directly...