Analyzing the Roots: Hydroponics and Halacha
Rabbi Zvi Goldberg Star-K Kashrus Administrator

The AeroGarden is a unique hydroponic system, enabling home-growing of vegetables. (Click here for more information.) The entrance of this system into the marketplace presents an opportunity to discuss the history and halachos of hydroponics.

According to some accounts, the Hanging Gardens of Babylon were hydroponically-grown.  The gardens hung strikingly from palace terraces and were considered one of the Seven Wonders of the World.  The gardens were supposedly constructed by Nevuchadnetzar around 600 BCE in present-day Iraq, about 30 miles south of Baghdad.¹  However, there is a lively discussion among historians as to who built the gardens, how they were planted, and indeed whether these gardens existed at all.  The Talmud (Avoda Zara 38b) itself discusses the hydroponic sprouting of seeds, in what seems to have been a fairly common practice.

More recently, in the 1930's, Dr. William Gericke of the University of California conducted research with hydroponics.  He coined the term "hydroponics", derived from the Greek words, hydro (water) and ponos (labor), or "water-working."  Put simply, it means growing plants in a nutrient solution without soil.  The science of hydroponics proved that soil is merely the holder of the nutrients, as well as the place where the plant roots traditionally live and a base of support for the plant structure.  Soil isn’t required for plant growth; the elements, minerals and nutrients that soil contains such as carbon, nitrogen, phosphorus, potassium and magnesium can be supplied in liquid solutions.  Plants are supported by porous material, such as sand, gravel, foam or glass wool, that acts as a wick in relaying the nutrient solution from its source to the roots.

In 1945, the United States Air Force built one of the first large hydroponic farms on Ascension Island, a barren island in the South Atlantic, followed by additional farms on Iwo Jima and Okinawa in the Pacific.  These hydroponic farms helped to supply fresh vegetables to troops stationed in these areas.  Over the past few decades, researchers in Israel have been at the forefront of hydroponic study.²

Presently, the most common hydroponic crop grown in the United States is tomatoes followed by cucumbers, lettuce, herbs, and peppers.  In addition, every day many hydroponic vegetables are brought in from Canada, Mexico and Europe.

Now let’s discuss the various halachos which are applicable to the AeroGarden, and to hydroponics in general.

Brocha
The brocha on hydroponically-grown vegetables is Shehakol.³  The brocha of Hoadama is applicable only to vegetables which actually grow from the adama, the earth.⁴  As noted above, many commercially sold tomatoes are grown hydroponically.  Still, unless one knows definitively that the produce was grown hydroponically, one should assume it was earth-grown and recite Hoadama.⁵  It is important to note that Israeli exported greenhouse-grown romaine lettuce (Alei Katif brand) is not grown hydroponically.  The brocha on these vegetables is Hoadama.⁶

Insects
Star-K’s certification of the AeroGarden is essentially a statement that the system is an appropriate method of controlling insects in produce.  Plants grown under controlled conditions indoors are generally free from insects which are commonly found in outdoor-grown plants.⁷However, we cannot guarantee that vegetables grown with the kit will be insect-free, since insects which commonly thrive indoors may find their way onto the vegetables.  In addition, in rare cases insects could possibly land on the plants by entering the home on clothes or other vegetables.  For these reasons, a cursory inspection and a washing of the vegetables before use is advised.  As an additional precaution against infestation, one may create an insect barrier by covering the garden with a mesh or cloth.

In addition to romaine and other types of lettuce, one can grow herbs such as cilantro, dill, and parsley.  Herbs are especially prone to infestation, are difficult to check, and are not widely available to the kosher consumer as ‘certified insect-free’.  The kit is helpful in controlling infestation for these varieties.

Hydroponically-grown vegetables (lettuce, herbs, etc.) sold commercially without kosher certification should be thoroughly checked since they grow under conditions unknown to the consumer.

Shabbos/Yom Tov
Nurturing plants is one of the 39 melachos, prohibited categories of work on Shabbos and Yom Tov.  Therefore, on those days the seeds may not be placed in their base, nor may nutrients or water be added.⁸  There are also restrictions on some melachos on Chol Hamoed, and one should ensure that the proper nutrients and water are added before the onset of Yom Tov so that there is no need to add them on Chol Hamoed.

The vegetables may not be harvested on Shabbos or Yom Tov due to the prohibition of kotzer, reaping.⁹  On Chol Hamoed, they may be harvested for Chol Hamoed or Yom Tov use.  Although the AeroGarden lights go on and off during Shabbos, this is permitted since the system is automated without further input.¹⁰

Israel
Due to the special status of Eretz Yisroel, generally, vegetables grown there must have ma’asros, tithes, separated.  However, if the AeroGarden kit is used to grow vegetables in Eretz Yisroel, ma’asros need not be separated from the vegetables.  This is because hydroponically-grown vegetables are free from the obligation to separate ma’asros.¹¹  In addition, they may be grown during the Sabbatical year of Shmitta.¹²

On a related note, if the seeds in the kits were to come from Eretz Yisroel, the seeds would not be subject to the laws of ma’asros or Shmitta.  These seeds are not edible seeds, and the Mishnah in Ma’asros 5:8 states that non-edible seeds are not subject to ma’asros or Shmitta.¹³ In any event, Star-K has determined that the AeroGarden seeds are not from Eretz Yisroel.

Marror
Hydroponic romaine lettuce should not be used for marror at the Pesach Seder.¹⁴  The reasoning for this is as follows:  It is unclear whether the brocha of Hamotzi relieves one of the obligation to recite a brocha on marror.  Although marror is eaten during the meal and should perhaps not require its own brocha, it is not a ‘meal food’ eaten to satisfy hunger and may, therefore, still require its own brocha.  To circumvent this issue, the halacha states that Hoadama on the karpas is recited while having in mind to exempt the marror.¹⁵  However, the brocha on hydroponic lettuce is Shehakol; thus, the Hoadama on karpas would not be applicable to the lettuce.  This would place one in a questionable position—should Shehakol be said on the marror or not?  To avoid this dilemma, hydroponic lettuce should not be used for marror.¹⁶

Nutrient Tablets
Star-K has determined that the nutrient tablets used in the AeroGarden system pose no kosher issues.  Nevertheless, even if the nutrient tablets would be non-kosher, the plants would still be kosher.  Normally, items that have a non-kosher source of nutrition are, themselves, considered non-kosher.  However, the rule of zeh v’zeh gorem states that if the nutrition is comprised of kosher and non-kosher components, the resulting animal or plant is kosher.¹⁷  In any garden, including the AeroGarden, the water is kosher so the kosher status of the nutrients has no effect.

From early history to modern times, hydroponics has offered an alternative to earth-grown produce.  It is yet another way to appreciate the bountiful world Hashem has bestowed upon us.¹⁸