Quotation על בבא קמא 161:6

His field was sown cumin or with arum, he must not sow on top of them, since they produce crops only after three years. [A field of] grain among which sprang up some aftergrowth woad, alternatively an area of threshing-floors in which many species sprang up, alternatively [a field of] clover among which grew up a number of species of herbs, he is not obliged to weed them out. But if he weeded or cut down the weeds, they say to him: “Uproot it all, except for one species.”