The Integrated Homestead: The Multi-Functional Greenhouse

“The Integrated Homestead”

To this point, we have sketched some general principles and overall strategies. Now we will consider specific projects, focusing on the integrative possibilities for each.

Sheltered Growing

Extending the harvest season with sheltered growing is about imitating for naturally cold hardy plants an unusually mild winter—not transporting them in effect to Miami. That is, no gardener committed to sustainability aspires to grow tomatoes in January by pumping in ungodly amounts of artificial heat. Instead, the goal should be to give naturally cold hardy plants sufficient protection from the extremes to accommodate winter’s onslaughts.

One way to extend the season on a small scale is simply to grow salads like lettuces and chicories, and potherbs like spinach and kale, in a fall garden bed as usual. Then, when winter starts to nip, assemble a cold frame over them, and tuck a heavy mulch around the exterior sides to keep the surrounding ground from freezing.

Our Multi-Functional Greenhouse

A more ambitious alternative is to assemble an unheated greenhouse from a kit. I recommend the largest model you have funds and space for, since you will certainly discover more and more ways to use your greenhouse as the seasons roll.

Our greenhouse is 20×48 feet, a Paul Boers gothic kit (rounded peak at the top) with 1-½-inch steel arches. Here are some of the integrative ways we’ve learned to use our greenhouse:

Growing winter greens: Some are more hardy than others. My lettuces will succumb to a particularly severe chill, but the chicories offer fabulous salads right through the dead of winter. Tatsoi may also be more limited in the unusually cold temperatures, but spinach is basically un-killable in my climate (Zone 6b).

Winter forage for livestock: I reserve space in the greenhouse for growing cut-and-come-again green forages for my poultry—small grains, crucifers, peas. This vitamin-rich fare is a godsend at a time of the year when there are few other possibilities for fresh foods.

Winter shelter for livestock: Actually, a greenhouse can be used to house livestock as well, poultry and pigs for example. The body warmth from the animals, and the CO2 from their exhalations, benefits the growing plants. (There is more below about poultry in our winter greenhouse.)

Shelter for tender perennials: Some perennials are tender enough to be marginal in my area (rosemary, white sage, tarragon). If I take the trouble to transplant them into the greenhouse, I ensure that they survive to take up their tasks again when moved back to the garden, come spring.

Earlier crops in spring: I plant extra-early (by one to two months) crops of potatoes, carrots, cabbages, and tomatoes in the greenhouse, ensuring harvests from these crops much earlier than from their garden siblings. (Some varieties are better suited to greenhouse conditions than others.)

Starting warm-season transplants: The shelter and higher temperatures of the greenhouse allow me to start heat-loving summer crops like tomatoes, peppers, eggplants, and sweet potatoes for transplanting to the garden as large, rapidly growing transplants when the season is right.

Habitat for insects: The idea of encouraging beneficial insects with habitat plantings applies in the greenhouse as in the garden. A couple of seasons ago I set plantings of yarrow throughout the greenhouse beds. This past late winter and spring, I saw more lady beetles than ever before, and the aphid population was a fraction of what it has been in previous years. Once the beetles have achieved their task, they seem to migrate outside, perhaps ensuring an earlier start on their work in the garden.

Vermicomposting: I mentioned vermicomposting above as an excellent way to practice responsible manure management, produce fertility for our soil (earthworm castings), and even to provide a source of live, nutrient-dense food (harvested worms) for poultry (or pigs). Two years ago, I installed 40 feet of worm bins (4 feet wide, dug 16 inches into the earth), right down the center of my greenhouse. Since I needed that center access anyway, I didn’t lose much growing space to the worm bins. (The heavy-duty lids over the bins have been a great place to lay out construction projects, as well as to set up a table for a winter picnic, or benches for a class on a raw March day.) There is no better place to site a vermicomposting operation than in a greenhouse—the activity of the busy earthworms, including reproduction, continues through winter, without a dormant period.

Black Widow Spider

Our Lady of the Shadows

One caution about working in a greenhouse: It can provide good habitat for black widow spiders, who like dark, hidden spaces close to the earth. I try to avoid leaving clutter like plastic trays and cell packs lying around, but I see the shy lady of the shadows from time to time. (The undersides of the worm bin lids are also prime real estate.) These are beautiful and unaggressive spiders, as welcome in my greenhouse as the skinks and garter snakes that hang around in the worm bins. It is unlikely that the gardener will ever have a problem with the black widow, if he is careful where he puts his fingers.

Energy Issues of Greenhouse Use

The objection is sometimes made that a greenhouse is an unnatural and unsustainable use of energy and resources: The metal frame represents a lot of “embodied energy”—greenhouse plastics are made from petroleum. That is true. But the energetics of greenhouse growing must be measured first of all against actual energy-expenditure patterns in our current food system. The hydrocarbon fuels expended in moving a single shipment of lettuce from California or Chile to my state of Virginia is greater than the energy expended to create and cover my greenhouse. (Eliot Coleman has calculated that the fuel expended transporting a single head of lettuce that distance is more than three times the “embodied energy” in a square foot of greenhouse plastic.)

Local greenhouse growing can take us a long way toward rehabilitating an extravagantly wasteful food/energy system. Once we’ve made that step, we can focus on deeper sustainability issues farther down the road.