Purim - 5786

Purim - 5786

Rabbi Hal Miller

(Reminder: It is traditional that on Purim we read "Purim Torah". These are fashioned in the same way as regular divrei Torah, but are humorous, nonsensical, and often just plain silly. Any "rulings" of law herein are expressly disclaimed as being jokes, not serious.... Oh, and bear in mind you're supposed to be a little schicker when you read it.  --HM)

Those of you who have been following my writings over the past thirty-some years are aware of the "Halachot of" series I put out for Purim each year. This year, our discussion topic is the halachot of greenhouses.

What is a greenhouse? It is not a house that happens to be painted green, whether gingerbread or other construction material was used. It is not a dwelling place for people (although see below regarding patio furniture and reading rooms). It is not a dog run or place to stuff the kitty litter box or gerbil or parrot cage. It is not indoors nor underground with artificial light (although those may be permissible, they are not greenhouses and have their own set of halachot). It is, rather, "a place in the sun", a structure specifically for the growing and care of plants. One might ask, with all the space outdoors, why would we need a special house for plants? The answer is that this is to create a controlled environment, enabling one to grow plants that might not otherwise survive in the natural environment of a particular part of the world. So, what are the laws governing a greenhouse? We can divide them into categories: construction, utilities, purposes, space utilization, types of plants, and operational issues. In each category we must investigate the impact of geographical location.

I - CONSTRUCTION

What are the issues regarding construction? They include location and direction, materials, flooring type, drainage, and integration into the rest of the garden.

The halachah requires abundant sunlight, thus the shelter must be in a place not shaded by another building or large tree, which is also a requirement to avoid branches falling upon the rather fragile structure. Although there is room for a little lenience, the shelter must be placed on level ground for purposes of drainage, see a local posek for a ruling should a leveling foundation need to be constructed. The shelter may not be placed in a low spot in order to avoid water collection and mud puddles inside. It may not be placed without protection in an area that will be frequented by large animals, such as deer, cattle or sheep. Since most greenhouses have some form of angled roofline, the shelter must be built with one slope aimed toward the sun. In locations where the direct sun heats the greenhouse above the approved temperature range, one must place a shade net across that sloped roof. Since the roof is sloped and not in a place where one might end up walking upon it (which would probably break it), no fence is required around the edge. Although not the halacha, the minority opinion requires consideration of the current location of utilities that will have to be extended to the new shelter when determining location.

Although there are some options, requirements for types of materials are to be strictly observed in order to label this shelter a greenhouse. There are kits available that in most cases meet these requirements (and should carry an acceptable hechsher), and there are many approved sources for building plans (such as ou,org/greenhouses). Flooring must be a non-living substance, such as concrete, raised wood plank, brick or gravel. It must either allow water to seep directly through it, or channel it off somewhere. Putting the shelter on grass is rabbinically prohibited since one is not about to remove everything to mow once a week. The flooring must be integrated with (or serve as) the foundation for the shelter and must support both the weight of the building, weight of all the plant pots (and other stored things that manage to find their way inside) and weight of the people who will wander in and out regularly. Building design varies widely: inclined roof, A-frame, Dutch barn, geodesic dome, etc., and all are allowed. The frame must be either plastic pipe, wood or metal (although bricks are allowed up to ten tefachim on the bottom of each wall other than the door area, see above for non-level situations). The frame must allow for attachment of the roof, lighting and other utilities, and a method for hanging planters. There must be at least one door. In most cases, there will not be room for more than one doorway. The siding and roof must be made of glass or some form of translucent or transparent plastic, solidly attached to the frame. There must be at least one air vent for every five linear feet of floorspace in the length direction. Although optional, it is considered beautifying the mitzvah to add openable windows. During the construction process, one is required to "measure twice and cut once" to avoid resulting in two pieces shorter than the current need.

Like a sukkah, a greenhouse has minimum and maximum dimensions. One that is less than ten handbreadths tall, while it may be used as a planter, is not a valid greenhouse and does not fall under these rules. One that is taller than twenty amos (35-40 feet) is also not called a greenhouse. It must be long enough and wide enough to contain planter pots and at least most of the body of the person who will be tending the plants.

Unlike a sukkah, a greenhouse must have four complete walls. Each must be whole, top to bottom and side to side. The concepts of "bending" and "closing" do not apply to greenhouses. The roof of a greenhouse must be made of non-vegetation materials and must be complete.

During the planning process one must bear in mind two things: there will always be changes in use, and no matter how much planning goes in, one will end up saying, "well that didn't work". Semper Gumby (always flexible). One should also bear in mind the integration with the rest of the garden, such as a path to it so one does not need to traipse through mud, visual decoration like flower pots around the door, and the inevitable collection of garden gnomes that make their way into view.

II - UTILITIES

Halacha does not require installation of utilities, but if one chooses to do so, there are rules to observe. A greenhouse without electricity is still a greenhouse but the installation of utilities can extend the amount of time during the year that the greenhouse is productive.

Electricity and water do not mix well (although it can be spectacular to watch if you are at a safe distance) so great care must be taken during the planning and installation to keep them apart. Bringing utilities into a greenhouse requires some kind of "break in the close", a hole through the floor, wall or roof, which must be carefully engineered to ensure minimizing the loss of warmth inside or leakage of rain, see also critter control below. Separate access holes for drainwater, supply water and electricity are required. A ground-fault-interrupt device must be installed on AC electrical lines, and sealed boxes used for switches, power points or junction boxes, with a ground strap attached. A sink, if used, must have drainage to the outside. Lights, electric heaters, fans, and any extra-use power points must be installed away from possible water leaking, splashing or misting (which covers the entire interior), and the electrical devices must not exceed the load rating on the circuit(s) installed. Electrical systems may either be AC (120-240V) or DC (12V) depending on what is available in the location. In a case of need, battery-powered fixtures may be used.

Hydroponics requires, in most cases, a set of utilities. The rules for this are much the same as for non-hydroponic installations so will not be covered separately here.

Critter control is required. At a minimum, windows, vents and doors must be kept closed or screened when not in use. If using a kit and the vents on the kit do not have screens, one should make screens to fit but is excused should that not have been done, but the burden of spiders, ants and so forth falls upon such a person. Although not required, mousetraps, rabbit traps and the like should be used to protect planting areas used for vegetables or grains. Individual pots may be fitted with tops or screens to meet this requirement. Even though a cat or dog may be applied to the problem if done with care, one may not rely on the pet as the sole means of critter control. Bear in mind the need for pollenators, which are an exception to these rules.

III - PURPOSES

The primary purpose for a greenhouse is the growing of plants. They may be grown out of season, out of their usual geographic environment, or for almost any other reason. A greenhouse may be used for business production or for a home hobby without restriction. Installation of a sitting area is only allowed as a secondary purpose. Any individual greenhouse may be used for multiple purposes, even at the same time, so long as they are non-interfering.

IV - SPACE UTILIZATION

Before constructing a greenhouse one is required to lay out the space utilization plan. Since normally after construction, an original plan is no longer viable, one might wonder why this requirement exists, but the halacha is that it is required nonetheless. After construction of the basic shelter, one is required to modify the plan, even to the extent of starting the planning process over, in order to fit into the actual interior dimensions of the shelter that was built.

While it is valid to configure in a sitting/reading area, storage areas, sink, and open table top work areas, such areas are not required. They are allowed only so long as there remains sufficient room for the plants to grow. Patio furniture, reading lamps and a mini-refrigerator are allowed, provided they do not take up such a great percentage of the floor space that it impedes the primary use for plants, nor take up too much of the available electrical load. Setting forth a children's or pets' area is not a proper use of space except to the extent that it is to teach children (not pets who you do not want digging inside the shelter) about gardening, but it still must not impact the primary use of the greenhouse.

Shelving of some kind is required in order to set out trays and pots full of soil. Thus shelving must be strongly constructed and well anchored. Stand-alone furniture is acceptable. Rafters and studs may be used for hanging plants but they must also be constructed to handle the extra load. Floor space must allow for drainage and a walking area.

V - TYPES OF PLANTS

The definition of a weed is any plant that is growing in a spot where one does not want it. Weeds must be removed on a regular basis, year-round.

Halacha prohibits kilayim, the mixing of certain kinds of plants, and this law applies in a greenhouse as well as in a field. Laws of kilayim are not reviewed here as they are dealt with extensively elsewhere. Suffice to say that, for example, growing grain and grapes requires two greenhouses. Additionally for kashrut purposes, one may not plant Milkweed and Bullrush together, and by rabbinic extension, Bullrush with Goldfish Grass, or Milkweed with Cardinal or Robin Trillium. Butterfly Weed, Venus Flytrap and similar must be isolated to prevent bits falling into the edibles. Plants like Cattail or Tiger Lily must also be isolated from Dogfennel.

Otherwise, any plants are allowable.

VI - OPERATIONAL ISSUES

Since the purpose of a greenhouse necessarily involves water, and in most cases dirt, the shelter will become dirty of necessity. It is required that once a year everything removable be removed and the shelter hosed out, inside and out. This is best done when the outside air temperature is good enough for the person on the hose who is going to get wet, and warm enough to prevent formation of ice throughout. All storage areas must be cleaned out as well as the exposed areas. Electricity must be off at the time.

Trellising and staking requires advanced planning since in most greenhouses there is a low roofline. One may not cut through the roof to extend plants above.

Access to all plants is required for watering, pruning, weeding and fertilizing. It is permitted to use lengthy tools as required to accomplish these tasks and to minimize the amount of floor space dedicated to walking paths. Usually, planting in a greenhouse is done in containers of various types, but in-ground planting is allowed, and modifies the requirements of flooring noted above.

​Since all of this requires effort, it is not uncommon for greenhouses to transition into storage sheds in the second or third year. While this is a permitted purpose, it is a poor use of such a specialized and expensive structure and should be avoided.

​Purim Sameach!