Kilayim, Chapter 5, Mishnah 8. This mishnah deals with the question of which species are considered kilei hakerem (forbidden mixtures in a vineyard), and which are not, either because it is not customary to grow them or because they are not fit for eating.
"HaMekayem Kotzim BaKerem":
"HaMekayem kotzim bakerem" - this refers to someone who maintains thorn bushes inside his vineyard. "Mekayem" - even if he did not sow them himself, he allowed them to grow there.
"Rabbi Eliezer omer: kidesh" - in Rabbi Eliezer's opinion the thorns create the prohibition of kilei hakerem. The reason: in a place called Arav people were accustomed to maintain and grow these thorns, because they used them as fodder for camels; whereas in an ordinary place, outside of Arav, it is not customary to grow them.
"VaChachamim omrim: lo kidesh" - in the opinion of the Sages the thorns do not create kilayim in the vineyard, since in this place we are dealing with something inedible. Rabbi Eliezer, in contrast, holds that it is enough that in Arav the thorns are considered animal fodder in order to forbid them in another place as well.
And the reasoning of the Sages: "shelo kidesh ela davar shekamohu mekaymin" - a prohibition is created only by something that people grow and maintain in the place where we live at present.
Species That Are Not Kilei HaKerem:
The mishnah continues and lists several species that are not considered kilei hakerem, since they are not considered real food:
"Ha'irus" - some understand this to be the iris flower.
"VehaKisos" - some translate this as the ivy, a climbing plant.
"VeShoshanas hamelech" - some translate this as the king's lily, a type of white lily.
"Vechol minei zera'im" - seeds that are not fit for eating at all, which are grown for various other purposes. Since they are neither a vegetable nor a fruit, they do not create kilei hakerem.
Concerning all of these the mishnah rules: "einan kilayim bakerem".
The Kanbos and the Kinras:
"HaKanbos - Rabbi Tarfon omer: eino kilayim" - in his opinion it is not considered food fit for eating. "VaChachamim omrim: kilayim" - in their opinion it is indeed considered kilayim.
"VehaKinras - kilayim bakerem" - the kinras, which some understand to be the artichoke, is considered kilei hakerem, because it is fit for eating.
In summary: In this mishnah we learned the dispute between Rabbi Eliezer and the Sages regarding thorns in a vineyard, and the principle laid down by the Sages - "lo kidesh ela davar shekamohu mekaymin", meaning that the prohibition is determined only by something that it is the custom of the place to grow and maintain. We also listed the species that are not kilei hakerem - the irus, the kisos, shoshanas hamelech and all kinds of seeds that are not fit for eating, the dispute between Rabbi Tarfon and the Sages regarding the kanbos, and the kinras, which is kilayim because it is fit for eating.