Thats because plant patents cover varieties that won't really propagated themselves asexually naturally (or won't come true from seed). Tubers will keep propaga

Thats because plant patents cover varieties that won't really propagated themselves asexually naturally (or won't come true from seed). Tubers will keep propagating by themselves - you cant call out someone for infringing a patent on a potato if you miss one when harvesting and it makes more of itself. Although there's always grey area - plant reproduction is complicated! Tubers and seeds are however covered under plant variety protection, but that's a different legal code than patents.