Are products of cross-pollinization (hybrids) forbidden?
Question
I planted an African blue basil plant in my garden (in Israel). I recently learned that this plant is propagated through cross pollination of two other basil species. Is it permitted to keep this plant in my garden? I assume so but want to check. I would love to understand the analysis. Thank you!
Answer
This is a fascinating question, relating to the topic of hybridization and whether or not it constitutes the prohibition of grafting.
The original prohibition of kilei ilan involves physically grafting two different species onto one another. That is, inserting the branch of one species (scion) into a branch of another (rootstock), like a pear tree scion onto a quince tree rootstock, or a watermelon scion into a pumpkin rootstock (both common practice today and forbidden!). Each shoot is cut with special scissors and wrapped in special tape, until the plants fuse. Such trees and vegetables, indeed, should be uprooted and it is forbidden to care for them, including watering, fertilizing, etc. The ensuing fruit or vegetable, though, is permissible to eat.
Hybridization, in contrast, is the result of sexual reproduction in plants. One performs the act of pollination, namely: taking male cells of one species and pollinating them onto the female cells of the second species, where the product (if it succeeds) is an intermediate fruit or plant.
This process can occur in nature, without human intervention, and also by human involvement with artificial pollination. There is a dispute among the Acharonim as to whether this act is prohibited and if it can be compared to kilei ilan (or even to kilei beheima - interbreeding).
Since the end-result is a new species, the Chazon Ish holds that cross-pollination between two different species is forbidden, while others, including Rav Shaul Yisraeli (whose rulings we follow at Torah VeHa'aretz Institute), maintains that this is not included in the original Torah prohibition, involving physically connecting parts of different plants to one another.
However, there is another issue involved here. If the various plants involved are halachically considered the same species, even the authorities who prohibit cross-pollinating different species would allow for artificial pollination for the same halachic species (even if they are slightly different strains). I asked our chief agronomist, Dr. Mordechai Shomron, and he confirmed that both parent species—Ocimum kilimandscharicum (camphor basil, a perennial) and Ocimum basilicum 'Dark Opal' (a purple-leaved sweet basil, annual)—are halachically considered the same species.
In conclusion, according to all opinions, you may enjoy your African blue basil in your garden.
Below is a translation from our halachic encyclopedia on this topic (for the original - האבקה | אנציקלופדיה הלכתית - חקלאית | מכון התורה והארץ-'למעשה' אקטואליה הלכתית):
Laws of Kilayim (Forbidden Mixtures) in Artificial Pollination
As noted, one of the common practices in agriculture and agricultural research is artificial pollination. This action is frequently performed between different species. Contemporary halachic authorities have discussed whether this constitutes a prohibition of kilayim (forbidden mixtures), since on one hand, there is a fusion of two different species that produces a new plant, but on the other hand, the action is performed on parts of the plant that cannot exist independently as a full plant.
Some authorities[1] hold that the prohibition of kilayim includes any creation of a new plant that was previously unknown. Therefore, pollination—even when done only with parts of the flower and not with the plant’s branches—is prohibited. Their opinion is based on the words of the Chazon Ish,[2] who ruled that the prohibition of grafting (harkavah) does not depend on which part of the plant is being grafted, but rather on the result of the action.[3]
Others hold that the prohibition of kilayim applies only when grafting two branches, and when hybridization is done solely through flowers, this act is permitted.[4] The reason is that the stamen merely fertilizes the ovule but does not create it, and the development of the fruit comes from the ovary, the style, and the ovule itself.[5]
One of the implications of this dispute is how to relate to genetic engineering.[6]
Sources:
[1] Shevet HaLevi Vol. 9, §224.
[2] Chazon Ish, Kilayim 2:16.
[3] See Minchat Shlomo II:3 §20, who wrote that even pollination is forbidden when it results in a graft: It is indeed prohibited even if the grafting is done by merely spraying juice, which, if sown in the ground, would not grow at all—since ultimately “the field” is planted with two species. In contrast, with animal mating, the Torah said "your animal"—and in this case, it is not an animal, and the prohibition of mating applies only to two actual living bodies. It should be noted that Ma'adanei Eretz, Kilayim 1:5, was lenient and held that there is no prohibition in "introducing sap into a tree."
[4] Rabbi Yisraeli, Torah and the Land Vol. 3.
[5] Responsa Kerem Shlomo, Vol. 2 §1:19.
[6] See entry "Genetic Engineering." See also Rabbi Y. Efrati, Hilchot Sadeh 136, pp. 5–8, who wrote that ideally, one should not introduce bee hives into an etrog orchard located near other citrus orchards—even though there is certainly no prohibition of kilayim here, since no direct action is being done to the plant. Nonetheless, since the fertilization is carried out by another species, caution is advised.