The idea of keeping small livestock — chickens, rabbits, even worms, in the greenhouse for mutual benefit of plants and animals is not a new concept. Plants and animals mutually benefit each other outside the greenhouse in a multitude of ways… so inside a greenhouse? Why not? After all, animals also need shelter and they exhale carbon dioxide, whereas plants release oxygen and can benefit from the extra warmth released from the bodies of birds, mammals and to a smaller extent, the composting process of their droppings.
There really are, actually, a number of “why nots!” But with this article, we’ll discuss how some greenhouse growers have adapted the idea of using chickens and rabbits to benefit their greenhouses, as well as what to watch out for.
Chickens, especially laying hens, might seem like a possible beneficial addition to a greenhouse — laying eggs in nests below the plant tables, adding warmth to the greenhouse with body heat and their droppings falling down into a floor-based composting system. And more and more people are adding backyard chickens to their gardening projects, anyway. But unless fenced away from the plants growing on the upper tables, they’ll destroy the plants, even if the greenhouse is growing plants chickens don’t like to eat. These birds can easily hop up onto tables regardless of if they’re the heavier, flightless breeds. They love to scratch up soil and tear up the ground hunting for bugs and tender roots, and within a day or two, can make a greenhouse full of tables of plants look like it’s been vandalized.
However, some greenhouse owners are finding productive ways to use chickens just part time in their greenhouses with great success. Nettles Farm owned by Riley Starks operates on very small acreage on Lummi Island, one of many islands off the Northwest corner of Washington State. The farm supplies chefs across the country, as well as local islanders at the Saturday farmers’ market and several nearby restaurants. The farm produces heirloom tomatoes, washed salad greens, assorted vegetables including asparagus and outdoor free-range eggs.
They use the greenhouse for their heirloom tomatoes, seeing as though the summer temperatures aren’t warm enough for outdoor late-season tomato growing. Their tomatoes grow right in the ground in the greenhouse rather than up on tables in pots. One year, a disease took over the tomatoes in the greenhouse. So at the end of the season, they put their chickens in the greenhouse over the winter. The chickens eagerly scratched up the soil and any tomato growing residue. Their droppings went into the soil. New micro organisms and aeration was introduced to the soil and air. They eventually removed the chickens and planted tomatoes again and the tomato disease had been completely eradicated, not to mention the soil organically fertilized.
In another case, a homesteader regularly puts chickens in his greenhouse each winter, using wooden frames and chicken wire to keep the chickens away from the growing plants. The greenhouse gives them more room and light than the coop they usually dwell in during the summer. He surrounds his winter greenhouse with electronet fencing and deep mulch, allowing the chickens outside during the day, while they roost in the greenhouse at night keeping winter greenhouse temperatures warmer and adding carbon dioxide for the plants.
In a handful of other cases, henhouses have been built sharing a thin wall with a greenhouse, allowing the henhouse to act as a warmth buffer on the side of the greenhouse that would have ordinarily been the coldest. Ventilation between the two buildings allowed for somewhat of an oxygen/carbon dioxide exchange. Hens have also worked out well penned up with raspberries grown under the protection of a fruit cage that was occasionally covered with greenhouse cloth. The birds were removed during ripening and harvest, but otherwise, even though they did scratch up some of the shallower roots, the raspberries were well established, and the chickens kept the soil healthy, weeded, and kept invading insect pests away.
But as far as chickens full time in a producing greenhouse, besides the concern of them eating or tearing up greenhouse plants, chickens can overheat. So if the maximum temperature the greenhouse reaches exceeds what chickens can tolerate, they aren’t a good match in the summer. Chickens can die of heat stroke and have even been seen “panting” when overheated in various temperatures in the 80s. Outdoors, they seek shade and dig into the cool ground for relief.
Any time of year, their droppings need to be addressed. One greenhouse grower is convinced that ammonia from their droppings killed his greenhouse plants. So, obviously, air circulation, a balanced ratio of birds to plants, and a healthy composting method on the greenhouse floor need to be part of the overall system.
Rabbits are another possible greenhouse plant companion. Heat is radiated especially from their ears, and using rabbits to warm winter greenhouses has worked for greenhouse growers who also use the rabbits either as another product to sell (such as their meat, wool, composted droppings or offspring to breeders) or for homesteading purposes. There isn’t yet an exact science on numbers of rabbits to space ratios. Many greenhouse-with-rabbit owners simply say three or four rabbits will adequately keep an average sized greenhouse in a typical temperate climate winter well above freezing.
Winter greenhouse rabbits can also simply be family pets of the smaller greenhouse owner, or tamed ones as a customer draw if wanting to entice potential buyers to the greenhouse for direct sales. Growers who sell farmed products direct to customers both from indoor and outdoor growing systems know how important it is for their customers to have a memorable and unique experience at their farm. Farm animals are almost always a popular customer draw. Experiences with them help generates word-of-mouth promotion and acts as a form of positive branding for the farm.
Although some people raise rabbits for meat and angora wool, rabbits also provide excellent soil amendments for the greenhouse plants. Many have heard of the rabbit/earthworm combination. Rabbit pens are built over a vermiculture system. As their droppings and urine land on top of the vermiculture area, the worms turn the waste into worm castings. Unlike chicken droppings, rabbit manure is considered “cold” rather than “hot,” so it doesn’t as easily overwhelm composting worms or burn plant roots and some people even put uncomposted droppings right in with their plants’ soil or compost tea. (If a greenhouse grower is growing food for sale, however, he or she should check with local regulations on using raw manure of any kind near food plants. Food safety regulations are growing in number and a good many are blanket rules based on large commercial operations that have used pathogenetic manure from unhealthy factory farms on their crops — resulting in regulations that many feel don’t apply to the healthy smallholder — yet the law doesn’t always make exceptions for them.)
Though rabbits can’t fly like poultry, they can hop out of a pen sometimes as high as three feet without a top. Also, the European rabbit breeds that most people raise as farm animals are serious diggers. They’re programmed to dig deep tunnels underground and are often “long term project” oriented — meaning they’ll dig bits at a time and come back to it later, sometimes without their owners even noticing. If the greenhouse happens to be directly on the earth rather than a solid foundation, and the rabbits’ pens are open to the earth on the bottom, they can eventually burrow their way out. People solve this in various ways. One is to lay chicken wire at the bottom of the pen which stops them from digging. Another is to put pegboard at the bottom of the pen. It’s too hard for them to dig out of quickly. Eventually it has to be replaced as it breaks down, but it can compost right along with the rest of the rabbit droppings and litter. Just make sure the pegboard is purely heat-pressed wood and not coated with acrylic or embedded with other chemicals that can be detrimental to the rabbits or the future compost.
Rabbits can be even more susceptible to overheating than chickens, so most people use them as winter greenhouse companions only. They usually can’t take more than 82 degrees and succumb very fast. And while ammonia from urine can be a beneficial fertilizer, it is also released into the air quite quickly, and as described above about poultry in the greenhouse, too much rabbit urine has been known to release ammonia that growers believe damaged or killed certain plants. So once again, ventilation, a balanced ratio of rabbits to plants, addressing a healthy composting system for droppings and choosing plants that grow well in an enclosed animal/plant greenhouse are needed to make the system work.
Barbara Berst Adams is author of Micro Eco-Farming: Prospering from Backyard to Small Acreage in Partnership with the Earth as well as The New Agritourism: Hosting Community & Tourists on Your Farm. She also writes for Local-Farm-Living.com and MicroEcoFarming.com.