תלמוד על כלאים 3:4

MISHNAH: One does not sow mustard or saffron close¹²¹Without any bare strip between one crop and the other. As R. Simson notes, the reason for this Mishnah is not explained. The explanation of Maimonides in his Mishnah Commentary is contradicted by the Halakhah. Probably the correct explanation is given by Maimonides in his Code, Kilaim 2:18, that a crop of mustard or saffron surrounding a field of fifty by fifty (i. e., from a single furrow 200 cubits in length) is enough for a domestic crop (a commercial crop of mustard seed is defined in the next Mishnah as needing three bate rova‘).
The translation of חריע as saffron (crocus sativus) follows Targum Cant.,Arukh(s.v. חריע) and Rashi. The Gaonic Commentary to Ṭahorot and Maimonides define it as safflower (carthamus tinctorius), a red dye. In the Halakhah, חריע is defined as “yellow dye.” to a grain field, but one may sow mustard or saffron close to a vegetable field. One does sow close to a fallow field, a ploughed¹²²A field on which the stubs of the previous harvest have been ploughed under but which has not been sown with a new crop. field, a closure, a foot path, a fence ten hand-breadths high, a ditch ten¹²³All measurements given in the masculine are hand-breadths. deep and four wide, a tree giving shade on the ground¹²⁴The place under the tree free of superficial roots is not the tree’s domain; hence, it may be used. This excludes vines which go under specially stringent rules because they cause kilaim to become sanctified and forbidden. For any other crop, it is only necessary that fields or garden beds be clearly distinguished., and a rock ten high and four wide.