Well, not quite thin air, because plants, like the rest of us, require nutrients and water to grow. Although the word “aeroponics” does not show up in either of the dictionaries I use for handy reference, and is totally ignored by my spellchecker, it is actually common enough that it should be appearing in any current dictionary of the English language. I admit that I had no idea what the word meant when Yehudah asked me the following shaylah:
“To overcome the many problems that may be involved in purchasing products during shmittah, we want to purchase a large aeroponics kit and grow our own vegetables. Will this present us with any halachic problems in terms of either the laws of shmittah, or the laws of kilayim?”
And so I began my education about this subject. This is what I discovered:
Aeroponics is a method of growing vegetables or herbs without soil by spraying the plant roots with water and nutrients (as opposed to hydroponics where the roots are submerged in a nutrient solution). Although it can be done on a commercial scale, the company Yehudah contacted sells aeroponic kits for growing herbs and vegetables in the comfort of one’s home. Each kit includes the seeds and nutrients required for specific types of plants, a complete self-contained open-top growing tank that includes its own light fixtures, and instructions on how to make it all work. Just add water and electricity to run the pump and lights.
The company advises growing lettuce, herbs, tomatoes, peppers, or strawberries each in its own tank since they have quite different needs. Even so, it is possible that one might plant different varieties or species that are halachically kilayim close enough together to involve a shaylah of kilayim.
WHAT IS KILAYIM?
It is important to clarify a common misconception. The prohibition of kilayim is not the creation of a new species; it is the mere appearance that one is mingling two species together. This is why hauling loads with two species of animal, grafting different tree species together, mixing wool and linen in a garment, or planting grains in a vineyard, are all Torah violations of kilayim although these acts do not affect the genetic make-up of the species.
Yehudah’s question involves two halachic topics:
Could his desktop garden possibly violate the mitzvah of kilei zera’im, which prohibits planting two species together or near one another? Violating this prohibition requires three basic conditions, all of which Yehudah met:
A. The prohibition applies to herbaceous, as opposed to woody plants, meaning that it does not apply to trees and shrubs, but it does apply to vegetables and many herbs. Thus, one may plant seeds of different trees together, yet one is forbidden to plant a mix of vegetable seeds (Rambam, Hilchos Kilayim 1:6).
B. The prohibition of kilei zera’im applies only to edible crops (Rambam, Hilchos Kilayim 1:4). Thus, one may plant seeds of different ornamental flowers and grasses within close proximity.
C. It applies only in Eretz Yisroel (Gemara Kiddushin 39a), and is min haTorah according to most halachic authorities even today (implied by Rambam, Hilchos Kilayim 1:1). (However, note that Rashi [Shabbos 84a] contends that kilei zera’im is prohibited only midirabbanan, and Tosafos [Yevamos 81a s.v. mai] contends it is only rabbinic in our era because most of the Jewish people do not currently live in Eretz Yisroel.) Therefore, someone in Chutz La’Aretz may plant his backyard garden with a wide variety of herbs and vegetables without any concern for how close they are, whereas in Eretz Yisroel, someone planting a garden patch must be very careful to keep the different species separate (Rambam, Hilchos Kilayim 1:3). I will discuss later how far apart one must plant two species to avoid violating this prohibition (see Chazon Ish, Hil. Kilayim 6:1).
One may not plant in Eretz Yisroel during shmittah. Does planting this indoor garden in Eretz Yisroel violate the laws of shmittah?
Yehuda’s question requires analyzing the following subjects:
Do these mitzvos apply when planting indoors?
Would they apply when planting outdoors in a pot or planter that is disconnected from the ground?
Do they apply when one is not planting in soil?
Two Talmudic passages discuss whether agricultural mitzvos apply indoors. One occurs in Eruvin (93a), which prohibits planting grain in a vineyard planted underneath a roof that extends from a house. This passage implies that agricultural mitzvos apply within physical structures.
On the other hand, Talmud Yerushalmi (Orlah 1:2) discusses whether three agricultural mitzvos, orlah (the prohibition to use fruit produced in the first three years of a tree’s life), maaser (tithing produce), and shmittah, apply to indoor plants. The Yerushalmi rules that whereas orlah applies, there is no requirement to separate maaser on produce grown indoors. The Yerushalmi questions whether shmittah applies to indoor produce, but does not clearly conclude whether it applies or not.
WHY IS ORLAH DIFFERENT FROM MAASER?
The Yerushalmi notes that when the Torah instructs us to separate maaser, it states: You shall tithe all the produce of your planting, that which your field produces each year (Devarim 14:22). Since the Torah only requires maaser on produce of a field, there is no requirement to separate maaser from what grows indoors, since, by definition, a field is outside. Therefore, one need not separate maaser min haTorah when planting inside a structure even if one is planting directly in the soil floor of the structure. (The Rishonim dispute whether there is a rabbinic requirement to separate terumos and maasros when planting in the ground within a building, see Rambam and Raavad, Hilchos Maasros 1:10.)
However, when the Torah describes the mitzvah of orlah, it introduces the subject by stating When you will enter the Land (VaYikra 19:23). A tree planted indoors is definitely in the Land of Israel, and thus is included within the parameters of this mitzvah, even if it is not considered a field.
Do the laws of shmittah apply to produce grown indoors? Does shmittah apply only to a field, or to anything planted in the Land of Israel?
The Yerushalmi notes that when the Torah discusses the mitzvah of shmittah, it uses both terms, land (VaYikra 25:2) and field (VaYikra 25:4). It is unclear how the Yerushalmi concludes and the poskim dispute whether the mitzvah of shmittah applies indoors in Eretz Yisroel. Ridbaz (Hilchos Shvi’is end of Chapter 1), Chazon Ish, Shvi’is 22, and Pnei Moshe all rule that it does; Pe’as HaShulchan (20:52) rules that it does not. Most later authorities conclude that one should not plant indoors during shmittah, at least not in the soil. I will discuss shortly whether one may plant during shmittah indoors hydroponically or with a covered floor.
May one plant different species next to one another indoors? Does the prohibition of kilayim apply to produce planted under a roof?
Based on the Talmud Yerushalmi we quoted above, we should be able to establish the following rule:
Where the Torah commands that a mitzvah applies to the land, it applies whether the planting is indoors or outdoors, whereas when the Torah commands that a mitzvah applies to a field¸ it does not apply indoors. As noted above, an indoor area can never be called a field.
How does the Torah describe the mitzvah of kilei zera’im? The Torah states “you shall not plant kilayim in your field” (VaYikra 19:19), implying that the mitzvah does not apply indoors. Thus, we should conclude that there should be not prohibition min haTorah in planting herbs or vegetables proximately if they are indoors. (Nevertheless, both the Yeshuos Molko [Hil. Kilayim 1:1] and the Chazon Ish rule that kilei zera’im does apply indoors and apparently disagree with the above analysis. I will take this into consideration later.) However, it is probably prohibited midirabbanan according to the Rambam’s opinion that the Sages required tithing produce grown indoors.
At this point, the discerning reader will note a seeming discrepancy based on the Talmudic passage that I cited earlier. The Gemara rules that one may not plant grain in a roofed vineyard, implying that kilayim does apply indoors. This seemingly conflicts with my conclusion that one may plant different herbs or vegetables proximately indoors without violating the prohibition of kilayim.
THE SOLUTION: GRAPES VERSUS VEGETABLES
The answer is that there is a major halachic difference between the two cases: Planting grain in a roofed vineyard violates kilei hakerem, planting other crops in a vineyard. Although both kilei hakerem and kilei zera’im are called kilayim, kilei hakerem is a separate mitzvah and is derived from a different pasuk than kilei zera’im, planting herbaceous species together. The Torah commands us about kilei hakerem by stating: “You shall not plant your vineyard with kilayim (Devorim 22:9), using the word vineyard, not field. Whereas a field cannot be indoors, the Gemara teaches that a vineyard could be.
At this point, we have resolved the first of our questions asked above:
“Do these mitzvos apply when planting in a covered area?”
The answer is that planting kilayim species should seemingly not apply, although some prominent authorities disagree. Shmittah does apply according to most poskim.
We now progress to our next question:
Do agricultural mitzvos apply to plants growing in closed pots and planters in Eretz Yisroel that are separated from the ground and yet exposed to the elements?
The Mishnah (Shabbos 95a) teaches that someone who plants in a flowerpot that has a hole in its bottom, called an atzitz nakuv, violates Shabbos as if he planted in the earth itself. However, planting in a flowerpot that is fully closed underneath, called an atzitz she’aino nakuv, is forbidden only because of rabbinic injunction and does not involve a Torah-prohibited violation of Shabbos. The same categories usually apply to other agricultural mitzvos: plants in a pot with a hole in the bottom are equivalent to being in the ground itself; those whose bottom is completely sealed are included in agricultural mitzvos by rabbinic injunction.
Therefore, one must separate terumah and maaser from produce grown in pots or planters, whether or not the containers are completely closed underneath, and one would violate kilayim if one planted two species together.
(There are some exceptions to this rule. According to the Rambam [Hilchos Maaser Sheni 10:8] and Shulchan Aruch [Yoreh Deah 294:26], orlah applies min haTorah to a tree planted in a closed flowerpot. The reason for this phenomenon is that a tree root will, with time, perforate the bottom of its pot, and therefore it is already considered to have a hole and be part of the ground below. There are also poskim who contend that shmittah does not apply at all, even midirabbanan, to items planted in a planter or flowerpot whose bottom is completely closed.)
SHMITTAH IN A HOTHOUSE
What happens if you plant in a covered area in a pot that is completely closed underneath? May one be lenient since the pot is both indoors and is also an atzitz she’aino nakuv, which is not considered connected to the earth min haTorah? This question leads us directly to the following question that Israeli farmers asked about sixty years ago: May one plant in a hothouse during shmittah in a closed bottom vessel? As I mentioned above, although some authorities permit planting in the soil indoors during shmittah, the consensus is to be more stringent. However, many poskim permit planting in pots in a hothouse if its floor is covered with a thick material, such as heavy plastic or metal (see Chazon Ish, Shvi’is 26:4; Mishpatei Aretz pg.239; however, cf. Shu”t Shevet HaLevi who prohibits this).
AEROPONICS AND SHMITTAH
Based on the above discussion, we may conclude that most authorities contend that there is no shmittah violation to plant aeroponically provided that the bottoms of the tanks are metal or plastic.
We still need to explore whether desktop planting may violate the laws of kilei zera’im?
I concluded above that there is probably only a rabbinic prohibition of kilei zera’im on indoor planting, but that some prominent authorities prohibit it min haTorah. Can we offer a solution for Yehudah’s plans? To answer this we need to address another issue.
KEEP YOUR DISTANCE
As I mentioned in the beginning of this article, kilayim occurs when different species are mingled together. If there is enough distance between the plants, there will clearly be no mingling.
How far apart must I plant herbs or vegetables to avoid violating kilayim? The poskim dispute this issue, and there are complications involving how and what one is planting. I will however, go directly to the conclusion that affects our case.
Since the desktop garden involves only herbs and vegetables and only a single plant or a few plants of each species, the halacha requires only a relatively small distance between species. The poskim dispute whether one is required to plant at least three tefachim apart [about ten inches] (Rashi, Shabbos 85a) or it is sufficient for the plants to be only 1½ tefachim apart [about five inches] (Rambam, Hil. Kilayim 4:9; Shulchan Aruch Yoreh Deah 297:5). Min haTorah one is required to plant only one tefach apart, the additional space requirement is rabbinic (see Rambam, Hil. Kilayim 3:10). Furthermore, since the tanks are completely closed underneath, they have the halachic status of atzitz she’aino nakuv, a closed pot or planter, which are considered part of the ground only because of rabbinic injunction, but not min haTorah. We can therefore conclude that as long as the seeds are placed more than a tefach apart we avoid any Torah prohibition. As far as the possible rabbinic prohibition if the plants are only a bit more that one tefach apart, we could additionally rely on the likelihood that kilei zera’im does not apply indoors in an aino nakuv planter.
Having completed the halachic research, we corresponded with the company that produces the desktop planting kits, asking them how far apart are the holes in which one “plants” the seeds, and how many different herbs and vegetables can be planted in a single tank.
The company replied that the kit usually has seven holes, each four inches apart center to center. When planting peppers and tomatoes, which grow larger than the greens or herbs, the company recommends plugging four of the holes and using only three, which are far enough apart to avoid any kilayim issue according to our conclusion. However, when planting herbs and greens, the distance between the holes is just about the distance that might present a halachic problem. I therefore advised Yehudah to plant in alternative holes even when planting herbs.
Having concluded that there is no problem from either shmittah or kilayim with growing one’s vegetables aeroponically, we now face a different shaylah: Does one recite borei pri ha’adamah before consuming vegetables grown in thin air, or does one recite shehakol? But the discussion of that shaylah will need to wait for a future article.
SHMITTAH, KILAYIM AND SHABBOS BREISHIS
Both the laws of shmittah and those of kilayim have sources in Shabbos Breishis; shmittah because it is the seventh year, and thus is the land’s observance of Shabbos, and kilayim because it represents our responsibility to keep species consistent with the way Hashem created them (see Gemara, Sanhedrin 56b; Yerushalmi, Kelayim 1:7).