Question #1: Spelt

I understand that spelt is a type of wheat. May I plant a small patch of it next to my wheat field?

Question #2: Trees and Ornamentals

I purchased a property in Israel that has grapes and other trees and ornamentals growing on it. What do I do to avoid violating the prohibition of kil’ayim?

Question #3: Tomatoes

May I plant various types of tomatoes next to one another?

Foreword:

In parshas Ki Seitzei, the Torah teaches the mitzvah not to plant your vineyard with kil’ayim (Devarim 22:9), after which the Torah mentions two other kil’ayim prohibitions: doing work with different animal species together and wearing shatnez. In parshas Kedoshim, the Torah introduces several mitzvos called kil’ayim when it says, “You shall keep my laws. You shall not breed your animals as kil’ayim, you shall not plant your field as kil’ayim and you shall not wear kil’ayim shatnez garments” (Vayikra 19:19).

I have written many times about the prohibitions of wearing shatnez, grafting one tree min (species) onto another and crossbreeding animals, but I have never written an article devoted to this week’s topic — the kil’ayim prohibitions in a vineyard and in a field. Please note that this article is only a general introduction to these mitzvos and not halacha le’maaseh — the topics are far more complex than can be covered in one article. For this reason, the opening questions in this article are going to be left unanswered.

Kil’ei hakerem

Kil’ei hakerem is the prohibition of planting an herbaceous (meaning non-woody, i.e.  – a plant other than a trees or a shrub), cultivated plant in a vineyard or adjacent to a grapevine. This mitzvah applies min haTorah in Eretz Yisrael and as a rabbinic prohibition in chutz la’aretz (Orlah 3:9; Kiddushin 39a). It also includes planting above or below grapes, such as, if the vine is trained onto a trellis or other framework.

Kil’ei hakerem is the only instance in which the Torah prohibits using what grows in violation of the kil’ayim prohibition. Other kil’ayim mitzvos prohibit only the act, but what grows or develops as a result may be used. (The Yerushalmi, Kil’ayim 1:4, permits using even the cutting developed from a forbidden graft.)

There is a major dispute among tana’im and rishonim whether kil’ei hakerem applies even when planting one species other than grapes in a vineyard, or only when two species other than the grapes are planted in a vineyard. Rav Yoshiyah rules that the lo sa’aseh of kil’ei hakerem applies only when planting both wheat and barley (or any two other species that are kil’ayim with one another) in a vineyard. Since the Torah says, “You shall not plant kil’ayim in your vineyard,” Rav Yoshiyah understands this to mean that someone is planting two varieties that are kil’ayim with each other, in a vineyard, which compounds the prohibition.

Vineyard vs. vines

There are major halachic differences between a few grapevines and what is halachically called a vineyard. The most prominent difference is that it is prohibited to plant any type of grain or most vegetables within four amos (about seven feet) of a vineyard, whereas it is forbidden to plant only within six tefachim, which is less than two feet, of a grapevine that is not part of a vineyard.

What is a vineyard?

So, what is a vineyard?

The halacha is that a vineyard must have at least five grapevines growing, four of which are positioned in a rectangle or square. Exactly how the fifth vine is planted is unclear from the Mishnah (Kil’ayim 4:6), and is disputed by the halachic authorities. The Chazon Ish rules that a vineyard requires that the fifth vine continues in a straight line from two of the other vines. In other words, the minimum definition of a vineyard is two parallel grape plantings, one of at least three plantings and the other of at least two.

Others contend that the fifth vine can also be similar to the way one would envision, from a bird’s eye view, the location of the tail relative to the four legs of an animal standing in rapt attention. The four legs form a rectangle, and the tail is alongside the rectangle, but opposite the middle of a side rather than the continuation of one of its sides (Rambam, Peirush Mishnayos, Kil’ayim 4:6; Tosafos Yom Tov; cf., however, Rambam, Hilchos Kil’ayim 7:7).

If five vines have been planted this way, and alongside them many more vines were planted haphazardly, the disorganized vines might not be considered a vineyard, but individual vines. The practical difference is whether vegetables and grains may be planted nearby, as long as they are more than six tefachim from the vines, or whether the laws of a vineyard apply, which requires a much more substantive distance of four amos. In both instances, construction of a tzuras hapesach or other mechitzah will allow planting the vegetables or grains alongside the vines, as long as the mechitzah separates between the vines and the vegetables or grains.

One row of grapevines is not considered a vineyard, even if it contains hundreds of plantings (Kil’ayim 4:5). This means that one may plant vegetables or grains alongside the grapes, as long as there is a six tefachim distance between them.

Kil’ei hakerem in chutz la’aretz

The rules of kil-ei hakerem in Eretz Yisrael are stricter than they are in chutz la’aretz. In chutz la’aretz, there is a rule, kol hameikil ba’aretz, halacha kemoso bechutz la’aretz. For our purposes, this rule means that since the law of kil’ei hakerem in chutz la’aretz is only miderabbanan, Chazal ruled that whenever a recognized scholar ruled that a particular situation is not considered kil’ayim in Eretz Yisrael, even when the halachic conclusion rules against him, one may follow this minority position in chutz la’aretz. For example, since Rav Yoshiyah rules that kil’ei hakerem is prohibited only when planting two species (that are already prohibited together) in a vineyard, this is the only act of kil’ei hakerem prohibited in chutz la’aretz. However, in Eretz Yisrael, there is concern over planting even a single type of vegetable in a vineyard.

Kil’ei zera’im

Kil’ei hasadeh or kil’ei zera’im (two ways of referring to the same prohibition) is planting two non-woody (also called “herbaceous”) commonly cultivated plants or seeds near one another, planting one species very close to another, already-planted species, or planting the seeds of one species on top or inside a specimen of another species. This mitzvah applies only in Eretz Yisrael. In chutz la’aretz, it is permitted to plant two herbaceous plants next to one another, although some authorities prohibit planting the seed of one species on top of or inside another in chutz la’aretz (Rambam, Hilchos Kil’ayim 1:5; Tosafos Chullin 60a s.v. Hirkiv). Therefore, in Eretz Yisrael, someone planting a garden patch must be very careful to keep the different species separate.

Both prohibitions, kil’ei hakerem and kil’ei zera’im exist, even if the species are not intentionally planted together, but grew on their own (Kil’ayim 2:5). In this instance, if the two species are too close together, one either must pull out one, or, as we will see shortly, build a mechitzah between them.

Introductions

Several important introductions will facilitate understanding the laws of these mitzvos.

A. Firstly, many assume that kil’ayim prohibits hybridization or crossbreeding (two ways of saying the same thing) of unlike species, or, in simpler terms, attempting to mix genetic material and create new species. However, this approach is inaccurate, since only one of the many kil’ayim prohibitions, crossbreeding animals, attempts to create something that does not occur in nature. All the other mitzvos ban the appearance of mixing two species. This distinction is very important in understanding many of the laws of kil’ayim.

B. Secondly, for clarity’s sake, I will use the word “species” in this article to mean items that halacha prohibits “mixing.” The dictionary definition of the word “species” is “a pool of individuals that breed together and will not breed with other individuals.” However, neither halacha nor science uses this definition. Since this article is a halachic talk about kil’ayim, I will discuss only aspects of the halachic definition germane to these mitzvos.

What defines a halachic species? Although there is a great degree of uncertainty about this, certain principles can be derived from the various passages, particularly of the Talmud Yerushalmi Kil’ayim.

(1) Two varieties that naturally cross-pollinate are halachically considered one species (see Yerushalmi Kil’ayim 1:2).

(2) At times, similarity of leaves or appearance or taste of the fruit are sufficient evidence to consider two varieties as members of the same species (Yerushalmi Kil’ayim 1:5). Small differences are never considered significant (Bava Kama 55a). Thus, different varieties, one of which grows wild and the other of which is cultivated, are usually one species (Mishnah Kil’ayim 1:2). Frequently, the rules are difficult to define and, therefore, most authorities recommend not growing two similar varieties of squash or beans together.

C. It is also important to note that the definition of “species” for the laws of kil’ayim is not the same as it is for the laws of challah. Spelt and wheat are considered different minim for the laws of kil’ayim, notwithstanding that they are the same min for the laws of challah. (This means that dough made of spelt and wheat flour can combine to create enough dough to be obligated to separate challah, notwithstanding that wheat and spelt cannot be planted next to each other.)

Cultivated

D. As I mentioned above, kil’ei zera’im and kil’ei hakerem apply only to species that are cultivated or maintained in your location for food, forage, clothing, dye or other similar purposes. The Mishnah states that the laws of kil’ayim apply to a species called zunin,usually understood to be darnel, a ryegrass that, in earlier generations, was used as bird seed. Planting zunin in a field of barley, rye, oats or spelt violates the prohibition of kil’ei zera’im. (Why it is permitted to plant zunin in a wheat field [Mishnah Kil’ayim 1:1] is a topic that we will leave for a different time.)

Proximity

Planting two crop species together or near one another is prohibited as kil’ayim. How far apart the two species must be depends on several factors, including the layout of the planting and what and how much was planted. In some situations, when growing small amounts of certain vegetables, planting the two species in alternate patterns is sufficient to permit the planting, notwithstanding that the different species grow alongside one another (Kil’ayim 3:1; Shabbos 84b ff.).

Between two grain fields of different species — for example, one growing spelt and the other rye — there needs to be an empty area greater than ten amos squared, approximately twenty feet by twenty feet, between the two fields. On the other hand, between two kinds of vegetables, the requirement is that the separating area be only six tefachim squared, approximately two feet by two feet. And even the size of this requirement is only miderabbanan. Min haTorah there is a dispute among rishonim whether the distance is one tefach squared, or 1.5 tefachim squared (Raavad, Hilchos Kil’ayim). The Chazon Ish (5:1) ruled according to the Rambam, the lenient opinion, that requires only one tefach squared, approximately four inches by four inches.

Mechitzah

Although we usually think of mechitzah as a separation necessary in a shul, the word has significance in several other areas of halacha, and particularly in the laws of kil’ayim. For the purposes of kil’ayim, whenever one wants to plant two species and there is not enough space to allow this, a halachically acceptable separation between the plantings permits the planting (Kil’ayim 2:8; 4:6). The rules here are similar to what is called a mechitzah for other halachos, including permitting carrying on Shabbos, although, for the laws of Shabbos, the entire area must be enclosed by mechitzos on all sides. For the laws of kil’ayim, it suffices that there is a halachic divider separating the plantings from one another. Among the many ways that someone can separate the two areas is by building a wall that is ten tefachim tall (approximately 32-40 inches) or piling rocks to a height of ten tefachim. Another option is a furrow or crevice in the ground, either natural or dug, that is ten tefachim deep.

The Mishnah (Kil’ayim 4:4) notes that lavud, openings that are smaller than three tefachim (about ten inches), does not invalidate a mechitzah, and therefore a fence that is more open than closed, but is ten tefachim tall, is a valid mechitzah for kil’ayim purposes. Similarly, one may build a “wall” with sticks placed either horizontally or vertically every three tefachim, and it is a satisfactory mechitzah.

This means that someone may have a vineyard on one side of a fence, in which the grapes grow alongside the fence, and plant grain or vegetables on the other side of the fence; it is completely permitted, even though the two crops may be growing within inches of one another.

Gaps

Large gaps in the middle of a mechitzah may not invalidate it. The general halachic principle is that an area that is mostly enclosed is considered “walled,” even in its breached areas (Kil’ayim 4:4; Eruvin 5b). For example, a yard enclosed by hedges tall enough to qualify as halachic walls may be considered enclosed, notwithstanding that there are open areas between the hedges, since each side is predominantly enclosed either by the hedges or by the house. This is true as long as the breach is smaller than ten amos,about 17 feet (Kil’ayim 4:4). This means that someone may have a vineyard on one side of the hedges (inedible growths usually do not create prohibited kil’ayim), and grain or vegetables on the other side of the hedges, even though the two crops may be extremely close to one another.

Tzuras hapesach

The Gemara (Eruvin 11a) rules that a tzuras hapesach, which we customarily use to make to enclose an area to permit carrying on Shabbos, may be used to separate two species, so that there is no prohibition of kil’ayim. A tzuras hapesach consists of two vertical side posts and a horizontal “lintel” that, together, vaguely resemble a doorway. Thus, it is permitted to grow a vineyard on one side of the tzuras hapesach and grain or vegetables on the other side.

Weeding

What about weeds? Do weeds present a kil’ayim concern?

As anyone who gardens knows, the definition of a “weed” is whatever the gardener does not want in his garden. Halachically, if the “weed” is from a species that is not maintained in your area, it is not a kil’ayim concern.

Conclusion

Targum Onkelos (Vayikra 19:19 and Devarim 22:9) understands the word kil’ayim to mean “mixture.” However, other commentaries explain the origin of the word from the Hebrew root כלא, the same as the word beis ke’le “prison” (see Bamidbar 11:28). Rav Hirsch (Vayikra 19:19) explains that the root כלא means to hold something back, and that the plural form kil’ayim — similar to yadayim, hands, or raglayim, feet — means a pair. Therefore, the word kil’ayim means to pair together two items that should be kept apart.

Concerning this, Rav Hirsch (Vayikra 19:19) writes, “The Great Lawgiver of the world separates the countless numbers of His creations in all their manifold diversity, and assigns to each one of them a separate purpose and a separate form for its purpose.”

In addition, observing the laws of kil’ayim helps us remember how various species obeyed Hashem’s instructions to remain separate during their creation. This reminds the contemplative Jew that if the plants heeded Hashem’s word during the Creation, how much more are we obligated to obey His instructions!

Question #1: Wolf and Dog

Are wolves and dogs members of the same species?

Question #2: Bactrian and Dromedary

May I haul a wagon with two camels, a Bactrian and a dromedary?

Question #3: Tangelo

Is it permitted to crossbreed tangerine and grapefruit to create a tangelo?

Question #4: Crabapples

May I graft an apple branch onto a crabapple trunk?

Foreword:

At the beginning of parshas Noach, Rashi teaches us that, during the moral chaos that led to the Mabul, even members of the animal kingdom mated outside their species (min), something that no self-respecting and ethical animal would ever do.

At this point, we need to ask what is meant by min, which is usually translated as species. The dictionary definition of the word “species” is a pool of individuals that can breed together and do not breed with other individuals.

However, we will soon see that neither halacha nor science uses this definition. It is important that, when studying the Talmudic, aggadic and halachic topics germane to kil’ayim, we must understand properly the Torah’s meaning of the term “species.”

Crossbreeding

Many halachically knowledgeable people assume that the purpose of the laws of kil’ayim is to prohibit the hybridization or crossbreeding (two ways of saying the same thing) of unlike species, or, in simpler terms, not to attempt creating new biological species or to mix genetic material of different species. However, we will soon demonstrate that this assumption is specious, since it is inconsistent with halachic accuracy for two completely different reasons:

A. Most kil’ayim prohibitions have nothing to do with creating new species.

B. In numerous instances, the laws of kil’ayim permit mingling two varieties that are biologically different species, and there are situations in which the laws of kil’ayim prohibit mingling two varieties that are biologically considered members of the same species.

Types of kil’ayim

First, we will demonstrate that kil’ayim prohibitions rarely have anything to do with creating new species (point A). Mesechta Kil’ayim deals with six different mitzvos involving the intermingling of species:

1. Crossbreeding animal species. This prohibition is called harva’as beheimah, or sometimes simply harva’ah. In this instance, as in most of the cases of kil’ayim, there is no prohibition against using the product created by someone who violated the prohibition. Thus, it is permitted to use a mule, notwithstanding that mating a donkey with a mare to produce a mule violates a lo sa’aseh min haTorah.

2. Using two animal species to haul or work together. This mitzvah is usually called lo sacharosh, as in the words of the Torah: lo sacharosh beshor uvachamor yachdav,“Do not plow with an ox and a donkey together” (Devarim 22:10).

3. Grafting different tree species, harkavas ilan, which prohibits inserting a shoot or scion of one species into the wood stock, or lower trunk, of another species. Note that it is completely permitted to plant different species of trees next to each other (Yerushalmi, Peah 1:4).

4. Planting a non-woody edible plant, such as a vegetable or grain, in a vineyard. (A “non-woody” or “herbaceous” plant is a plant other than a tree or a shrub.) This prohibition is called kil’ei hakerem, and applies min haTorah only in Eretz Yisrael, although it does apply in chutz la’aretz as a rabbinic prohibition. This mitzvah is atypical in that it is the only prohibition of kil’ayim whose product is prohibited to use, min haTorah.

5. Planting two non-woody edible plants near one another. This mitzvah, called kil’ei hasadeh, kil’ayim of the field, applies only in Eretz Yisrael. In chutz la’aretz it is permitted to plant two herbaceous plants next to one another.

6. Wearing shatnez, clothing that includes both wool and linen. The prohibition is limited to wearing such clothing.

The two mitzvos of kil’ei hakerem and kil’ei hasadeh, apply min haTorah only in Eretz Yisrael, whereas the others apply min haTorah both in Eretz Yisrael and in chutz la’aretz.

I stated above that kil’ayim prohibitions usually have little or nothing to do with the creation of new species. Crossbreeding of plants involves pollinating the flower of one species with pollen from a different species. But none of the agricultural mitzvos listed above has anything to do with hybridization.

Let’s take a more careful look at the three agricultural prohibitions: 3, 4, and 5, above. In the cases of herbaceous, or non-woody, plants, kil’ayim is planting two crop species near one another (#5) or planting them inside a vineyard (#4). But planting the seeds of different species in close proximity does not change the DNA of the species or cause any hybridization, nor does it cause anything to grow of a variety different from either parent.

In the case of trees and shrubs, harkavas ilan (#3) means grafting one species onto another. When you graft a branch of one species onto the stock of another, the fruit that grows has the DNA of the scion branch and no DNA material of the species of the stock.

Also note that these three kil’ayim prohibitions are limited to species in which some part of the plant is edible.

Wool and linen

Wearing a garment that contains both wool and linen (#6) does not cause any hybridization. Wool grows on sheep, and linen is the product of a flax plant. Combining the two textiles in a garment does not affect their genetic material.

Lo sacharosh

Although some wish to explain that the prohibition of using two animal species to haul or otherwise be worked together is out of concern that someone will house them together or otherwise cause them to mate (Alshich, Devarim 23), there are many other ways to explain the “reason” for this prohibition (see, for example, Ibn Ezra, Devarim 22:10).

Harva’as Beheimah

The only one of the six kil’ayim prohibitions that involves hybridization is harva’as beheimah. But I presume that my readers agree that it is very strange to provide a reason for six different mitzvos that does not apply to five, or, possibly, not to four of them!

And, although we usually translate the word kil’ayim as “mixture,” some commentaries associate this word with the root כלא, as in the word “prison,” beis ke’le. Rav Hirsch explains the root word ke’le as holding something back, keeping someone incarcerated. The plural form kil’ayim is structurally similar to yadayim, raglayim or kesafayim,and means “a pair.” Thus, the word kil’ayim means pairing together items that should be kept apart (Hirsch Commentary to Vayikra 19:19), a definition that fits all six categories of kil’ayim, but has nothing to do with hybridization.

Dogs and wolves

My second point above (point B) is that there are numerous instances where the laws of kil’ayim permit mingling two kinds that are biologically considered different species, and there are also many instances in which the laws of kil’ayim prohibit mingling two kinds that are biologically considered the same species.

To explain, I will first pick examples in the animal world and then in the plant world. The Mishnah (Kil’ayim 1:6) states that wolves and dogs are kil’ayim together; it is forbidden to crossbreed them or to have them haul a load together. Yet, wolves and dogs breed together freely in the wild. Thus, we see that kil’ayim is not dependent on whether the varieties breed together.

From the Yerushalmi and the halachic authorities it appears that several factors are used to determine whether two varieties are considered different species, including how mankind views them, as the Torah teaches, “Hashem had created… all the animals of the field and the birds of the sky and He brought them to the man to see what he would call them… And the man gave names to all the domesticated animals and the birds of the sky and the animals of the field (Bereishis 2:19-20). This implies that man understood the purpose or uniqueness of each species and how it should be categorized, separately, from all other species.

Scientific dogs

The scientific system for classifying species, developed by Carl Linnaeus in the eighteenth century, names every species by two words: the first, its genus, which is capitalized, and the second, a lower case word for its species. Occasionally, a third word, also lower case, is added to indicate subspecies, which can also be called race, ethnic group, breed, variety or cultivar. (Humans are divided into races and ethnic groups, dogs into breeds, fruits and vegetables into varieties – or cultivars for boutique products.) Linnaeus categorized dogs as Canis familiaris and wolves as Canis lupus,meaning that he considered them two separate species. Today, most scientists categorize domesticated dogs as Canis lupus familiaris, which means that Canis lupus refers to a single species that includes both wolves and dogs, and familiaris is added for any domesticated dog breed.

An interesting comparison can be made with the dingo, a non-domesticated Australian dog. I checked Wikipedia regarding the dingo’s classification, and found the following: “The dingo, Canis familiaris, Canis familiaris dingo, Canis dingo, or Canis lupus dingo, is an ancient lineage of dog found in Australia. Its taxonomic classification is debated, as indicated by the variety of scientific names presently applied in different publications. It is variously considered a form of domestic dog not warranting recognition as a subspecies (Canis familiaris), a subspecies of either dog or wolf (Canis familiaris dingo or Canis lupus dingo), or a full species in its own right (Canis dingo).” I note that Wikipedia assumes that wolves and dogs are considered separate species.

The contemporary scientific world no longer defines a species by its ability to breed together and not to breed with a different species. As contemporary science has reinvented itself in the modern world, including its widespread misconceptions of spontaneous evolution of species and its unproved hypotheses regarding the origin of species, it can no longer use the definitions of breeds as its basis for defining species. This is because it accepts that species eventually mutate naturally into new species, which rejects or modifies the traditional definition of a species breeding within itself. As a result, science is forced to redefine “species” on the basis of similarity of DNA, but this piece of information has as yet not been communicated to the dictionary editors.

Camels

I have just demonstrated where, halachically, something can be considered two different species, notwithstanding that they breed together. I will now pick an example in which halacha considers two varieties to be the same species, notwithstanding that modern science categorizes them as separate species. The Gemara teaches that the one-humped Arabian camel, the dromedary, and the two-humped Bactrian camel (“Persian camel,” in Chazal’s lexicon) are, without question, one species. (By the way, “Bactria” was an area of ancient Persia; thus, Chazal’s method of distinguishing between the two varieties of camel is identical to modern nomenclature.) The Gemara states, rhetorically: “do you consider them different species, simply because one variety has a longer neck?” (Bava Kama 55a). Obviously, minor differences in physical characteristics are insufficient reason to treat two varieties as halachically different species.

Modern science counts three surviving species of camel, and, based on fossil remains, five extinct species. (How can one tell whether two extinct individuals could breed together or not?) The three existent species are Camelus dromedarius, the one-humped Arabian camel; Camelus bactrianus, the two-humped, domesticated variety; and Camelus ferus, the only remaining variety of wild camel, which lives today in desert areas of northwestern China and southwestern Mongolia. Formally, scientists will tell you that Camelus ferus is considered a separate species on the basis of genetic studies. Informally, they may admit that it is categorized as a separate species in order to facilitate research grants. Research money is more readily available to study “species” that are critically endangered than critically endangered “subspecies.”

Spelt wheat

Thus far, I have demonstrated that, in the animal world, halacha’s category “min,” and modern science’s nomenclature “species” do not necessarily coincide. Now, I will show that this is equally true in the plant world. Modern science does not consider wheat to be a species, but to be a genus, a group of related species, Triticum. Linnaeus categorized wheat into five different species, including spring wheat, winter wheat, Einkorn, and spelt as separate species. However, halacha recognizes spelt as one species and the other varieties as different forms of the species, wheat (Kil’ayim 1:1, see Rash and Rambam). Thus, it is permitted to plant different wheats together, or alongside one another, even in Eretz Yisrael, whereas one may not plant wheat and spelt together or alongside one another, without following the rules established for kil’ayim of two different species.

Citrus

Science treats the various citrus fruits as species of the same genus. Thus, esrogim are Citrus medica; grapefruits, Citrus paradise; lemons, Citrus limonia;and tangerines are a varietyof Citrus nobilis called Citrus nobilis deliciosa. Yet, based on his extensive analysis of halachic sources, the Chazon Ish (Kil’ayim 3:7) considers lemons, esrogim, grapefruits and oranges to be the same species as regards the laws of kil’ayim, which would permit grafting a grapefruit tree onto a lemon stock. (However, in a different place, the Chazon Ish is hesitant about this decision and rules against relying on it [Hilchos Kil’ei Ilan 178:9]. His concern in the latter place is the difference in appearance of the various fruits. He also rules that chushchash, a variety of wild orange, and the oranges that we eat and juice are the same min for halachic purposes [Hilchos Kil’ei Ilan 178:11].) The Chazon Ish notes that his discussion is germane only to the prohibition regarding harkavas ilan, meaning that it is permitted to graft an esrog branch onto the stock of a different citrus for the objective of consuming the produce. However, an esrog grown this way will not be kosher to use as one of the four minim on Sukkos. (See Shu’t Rema #117; #126:2; Shu’t Maharam Alshich #110; Levush, Orach Chayim 649:4; Taz and Magen Avraham, Orach Chayim 649; Shu’t Bach #135 et al., all of whom agree that an esrog grafted onto a different species is not kosher for Sukkos use. The Shu’t Panim Me’iros, Volume II #173, and the Saba Kadisha,are among the small minority of authorities who permitted using an esrog grafted onto non-esrog stock for the four minim on Sukkos.) In other words, according to most authorities, an esrog grafted on lemon stock is not kosher for the mitzvah on Sukkos, notwithstanding that the grafter may not have violated any prohibition.

Tangelo

We can now discuss the third of our opening questions: “May I create a tangelo by crossbreeding a tangerine and a grapefruit?” Although the Chazon Ish did not discuss tangerines, it would seem that, according to his comments in Kil’ayim 3:7, this would be permitted, and that, according to his comments to Yoreh Deah, it would not.

Crabapples

At this point, we should examine the last of our opening questions: May I graft an apple branch onto a crabapple trunk?

The regular eating-apple is usually called Malus pumila. There are numerous varieties of crabapples, most of which are also included in the genus Malus and are called names such as Malus coronaria, Malus angustifolia and Malus ioensis. Many of these crabapples freely hybridize in the wild with apple cultivars. Thus, we see again that the dictionary definition of a species is no longer accepted by the scientific community.

What is the halacha of grafting apples onto crabapple stocks?

The Mishnah states that apples are kil’ayim with chazrad, some type of wild apple or other fruit bearing some resemblance to, or characteristics, of an apple. Some rishonim believe that chazrad is a variety of wild apple that produced a fruit that was used as feed, but was not considered suitable for human consumption, even after pickling or stewing. However, we do not really have any idea what species or variety chazrad is.

In early nineteenth-century eastern and central Europe, we suddenly find several major halachic authorities debating whether some variety of crabapple or wild apple could be used as the stock on which to graft edible apple trees. The crabapple fruits were usually not considered edible.

The Torah scholar who addressed this question to the author of Shu’t Mishkenos Yaakov considered grafting apples onto crabapple stocks a problem, quoting the Levushei Serad (Chiddushei Dinim #106, also quoted by Piskei Teshuvah, Yoreh Deah 295:2) that this graft is prohibited as harkavas ilan. The Mishkenos Yaakov (Shu’t Mishkenos Yaakov, Yoreh Deah #69) discusses some of the varieties of crabapple that were commonly used for grafting apples, and permits grafting an apple scion onto the stock of any of the crabapples available in his area. This conclusion is accepted by several other authorities (Beis Efrayim, quoted by the Mishkenos Yaakov; Shu’t Tzemach Tzedek, Yoreh Deah #221; Aruch Hashulchan, Yoreh Deah 295:15). Thus, again, the difference in scientific species identification has nothing to do with the halachicdefinition.

Conclusion

In all six types of kil’ayim mentioned above, the general criterion is to avoid the appearance of different species being intermingled. Concerning this, Rav Hirsch (Vayikra 19:19) writes, “The Great Lawgiver of the world separates the countless numbers of His creations in all their manifold diversity, and assigns to each one of them a separate purpose and a separate form for its purpose.”

In addition, the laws of kil’ayim help us bear in mind how various species obeyed Hashem’s instructions to remain separate during their creation. This reminds the contemplative Jew that if the plants heeded Hashem’s word during the Creation, how much more we are obligated to obey all His instructions.

Parshas Kedoshim contains one of the two places in the Torah where the mitzvos of kil’ayim are taught.

Question #1: Kil’ei beheimah

May one attempt to crossbreed a mule with a stallion?

Question #2: Kil’ei zera’im

May I plant the vegetables in my garden close together?

Question #3: Kil’ei hakerem

Is there any way that I can plant vegetables near my vineyard?

Question #4: Harkavas ilan

Must I be careful before I purchase a fruit tree?

Many people assume that the halachic definition of the mitzvah of kil’ayim is the crossbreeding of different species of plants or animals, but, as we will soon see, not all of the laws of kil’ayim have to do with what a farmer or a scientist would call crossbreeding or hybridization.

My desktop dictionary defines hybrid as “the offspring produced by breeding plants or animals of different varieties, species, or races.” Thousands of years ago, mankind crossbred horses and donkeys to create mules and hinnies. This hybrid, called a pered (female pirdah) is already mentioned many times in Tanach. As a pack animal, the mule — produced from a male donkey, called a “jack” and a mare (female horse) — has many advantages over either of its parents. It is usually as strong as a horse, sturdy, sure-footed, and, notwithstanding its reputation for being “stubborn as a mule,” is more reliable for hauling than draft horses. (A hinney, which has less commercial value, is produced from a stallion (male horse) and a female donkey, called a “jenny.” The word “hinney” comes from its parents – a horse and a jenny.)

Other crossbred animals

Artificial insemination has been used to crossbreed camels and llamas with the goal of producing a larger quantity of quality llama wool. Mankind has created such interesting creatures as ligers, crossbreeds of male lions and tigresses, tiglons (sometimes called tigons) from male tigers and lionesses, leopons (male leopards and lionesses), wholpins (whales and dolphins) and geeps (goats and sheep). Most of these have resulted in limited, if any, commercial value, although it was thought by some that they might.

Crossbreeding animal species is one of the prohibitions of the Torah when it declares behemtecha lo sarbia kil’ayim (Vayikra 19:19). It is one of the unusual mitzvos that even a non-Jew is required to observe (Rambam, Hilchos Melachim 10:6).

The prohibition is only to create the crossbreed; one may use a mule or any other crossbred animal. However, not only is it prohibited to crossbreed a horse with a donkey, it is even forbidden to attempt to breed a mule or hinney with either a donkey or a horse (Mishnah, Kil’ayim 1:6). In fact, it is rare that such an attempt will produce offspring, although it is claimed anecdotally that this can happen upon occasion. Nevertheless, someone who attempts to crossbreed them violates a Torah prohibition.

Crossbreeding of plants

Crossbreeding of plants, or, as it is usually called, cross-fertilization or cross-pollination, is when one pollinates the flower of one species with pollen from a different species, to produce offspring with some characteristics of each. Many fruits have been developed this way, although I want to share that a nectarine is not a crossbreed of a peach and a plum, as often mistakenly thought. A nectarine is an ancient variety of peach (Prunus persica) that has a smooth skin. Botanists consider it to be the same species as peaches.

What is interesting is that, in the discussions about kil’ayim in the Torah, the Mishnah and the writings of Chazal, nowhere does it say that it is prohibited to cross-pollinate from one plant species to another. This does not mean to say that there is no prohibition of kil’ayim germane to trees or plants. Quite the contrary, there are three such prohibitions min haTorah. They are referred to as kil’ei zera’im, kil’ayim in plants; kil’ei hakerem, kil’ayim in vineyards; and kil’ayim in trees, usually referred to as harkavas ilan. But, as we will soon see, none of these three prohibitions has anything to do with crossbreeding.

Kil’ei zera’im

Kil’ei zera’im is planting two or more different species of grains, vegetables or other edible herbaceous plants in close proximity. Exactly what defines “close proximity” is a very complicated halachic topic, and depends on factors such as the shape and size of the vegetable patch, and what variety of produce one is planting. We should note that, from a botanical point of view, planting two species in close proximity will not cause hybridization because it does not affect the genetic makeup.

This mitzvah applies only in Eretz Yisroel. Thus, someone in chutz la’aretz may plant his backyard garden with a wide variety of vegetables without any halachic concern, whereas in Eretz Yisroel someone planting a garden patch must be very careful to keep the different species separate.

Kil’ayim in a vineyard, kil’ei hakerem

Kil’ei hakerem is the prohibition against planting grains or vegetables in, near, above or below a vineyard. Again, this forbidden planting will not affect the genetic makeup of any of the plants involved. It is also clear that this was not the concern in halacha as we see from many of the halachic details. Here is one example: Although it is prohibited to plant grains or vegetables near a vineyard, there is a way to permit it by separating the vegetable patch from the vineyard with a halachic wall between them. For example, if one places two poles and a wire across the top, a tzuras hapesach, between the vegetable patch and the vineyard, it is permitted to plant vegetables right next to the vineyard (Eruvin 11a). This is similar to what we do when we construct an eruv to permit carrying on Shabbos. It is quite clear that, botanically, the tzuras hapesach does not accomplish anything to prevent the mingling of the species. Yet, with the tzuras hapesach, it is permitted to plant the crop; without the tzuras hapesach, it is a Torah prohibition to do so! This certainly cannot be explained on a scientific basis.

Even one grapevine is problematic near a crop plant, so care must be taken even in the home garden. For example, a pot with herbs or a vegetable under a trellised grapevine could forbid the grapes and the produce of the pot!

Unlike other forms of kil’ayim, the produce of kil’ei hakerem is forbidden to use.

The prohibition of planting grains or vegetables in a vineyard applies in chutz la’aretz, but only miderabbanan (Kiddushin 39a).

Harkavas ilan – grafting trees

The laws of kil’ayim also prohibit grafting one species of tree or plant onto the wood stock, or lower trunk, of another species. Although a town dweller may feel that this is a rare occurrence, in fact, contemporary plant nurseries and tree farmers usually graft branches of a species that produces delicious fruit onto the hardier stock of a different species.

For example, most peach and nectarine trees are produced by grafting a peach or nectarine branch onto the stock of a hardier tree, such as an almond. Someone who performs this, either in Eretz Yisroel or in chutz la’aretz, violates a Torah prohibition whether he is Jewish or not (Rambam, Hilchos Melachim 10:6). Most authorities rule that one may not own, water or prune a kil’ayim tree, whether or not it is in Eretz Yisroel or in chutz la’aretz (Shulchan Aruch Yoreh Deah 295:7 and Piskei Teshuvah).

However, many observant Jews purchased agricultural properties that contained kil’ayim trees and did not cut down those trees. Was there any justification for their actions? Numerous halachic responsa discuss what was apparently a widespread practice in the eighteenth and nineteenth century. Whereas most poskim rule that these Jews violated the halacha, some authorities justify the practice of owning these trees, at least in chutz la’aretz (Shu’t Chasam Sofer, Yoreh Deah #288; Aruch Hashulchan, Yoreh Deah 295:17-18).

Because so many trees are grafted nowadays, someone who owns a fruit tree should have a horticultural expert check whether its stock is from the same species or not. Often, even a non-expert can detect if a tree was grafted onto a different species by simply scrutinizing the tree. If the bark somewhere near the bottom of the tree looks different from the upper part of the tree, this indicates that the upper part of the tree was grafted. Often one can see a line separating the grafted scion from the rootstock, or a difference in thickness between the top and bottom. Before purchasing a new tree at a nursery, examine the trunk carefully for signs of grafting.

The prohibition of planting vegetables and other edible crops together applies only in Eretz Yisroel, whereas grafting trees applies equally min hatorah in chutz la’aretz and in Eretz Yisroel.

Although planting and caring for a kil’ayim tree is forbidden, the fruit from such a tree is permitted. Thus, one may purchase fruit in a market without worrying about kil’ayim.

Esrogim

Although space does not allow us to discuss this fascinating topic, there is a huge amount of halachic literature discussing the very common instance of using an esrog from a tree that was grafted onto a non-esrog tree. Most authorities rule that this esrog may not be used to fulfill the mitzvah on Sukkos.

Conclusion

Rav Hirsch (Vayikra 19:19) explains that the root word ke’le means to keep or hold something back, and that the plural form kil’ayim is similar to yadayim or raglayim and means a pair. Therefore, the word kil’ayim means to pair together two items that should be kept apart. This is to teach us that although we are given the world to develop, we must follow the rules that Hashem established for us to do so.