The Greenhouse as an Ecosystem

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[3] GROW WHAT YOU LIKE TO EAT, SMELL, OR LOOK AT

Finally, we can discuss what really counts: the green goods! Now you can appreciate how much effort is put into controlling the environmental factors to enhance the indoor garden. Before we leave physical science, though, remember that the greenhouse environment will determine which crops will thrive there. The successful gardener considers light quality and quantity, photoperiodism, heat requirements, and nutrition for every crop.

PLANNING AHEAD: The next criterion for a productive greenhouse is adequate planning. Mistakes on paper are easier to correct than mistakes cast in the soil. The first year will be the most difficult, because you won't be familiar with the greenhouse's air or soil temperatures. However, with this little manual to guide you and with the listed references as a more comprehensive resource, you should be able to make intelligent guesses.

Whether your interior layout is in beds or benches, design the first season's planting with proper lighting in mind. Which areas have the brightest light, partial light, or shade? In winter, place vining or tall plants where they won't shade medium or lower-canopy ones. Two-or three-strata planting (rows placed like benches in a stadium) makes for efficient space utilization. Resist overcrowding; doing so will pay off in the long run. Cramped plants are vulnerable to diseases and may never reach full size.

Almost everything we grow in our bioshelters at New Alchemy Institute is put there as a young transplant. This practically guarantees 100% survival. (Seed sowing and seedling development are confined to a reserved nursery area.)

After you've selected your crops, figure out how long it will take them to develop to transplant size. Then you'll know when to sow the seeds. For example, I transplant my fall crop of tomatoes in late July, and—since tomato seeds germinate in three to five days and require five to six weeks to mature into hefty-size seedlings—I must sow them in mid-June.

Devise your planting schedule for a 12-month period. Account for sowing, plant development, and harvest. Select vegetables that yield for long periods. (A friend once harvested tomatoes from the same plant for 16 months!) Adjust your timetable to the climate and weather conditions in your area.

SUCCESSION PLANTING: Within the greenhouse's. cool and warm seasons, there's some flexibility about when you can sow your crops. Use this to your family's advantage by budgeting your planting space. For simplicity, let's say your greenhouse has three growing beds, all with similar light quality. Plant the first bed on January 1 with Burpee's Green Ice loose-leaf lettuce and Deci-Minor, a butterhead lettuce. Two weeks later, plant Grand Rapids Forcing looseleaf lettuce and a Dutch original buttercrunch, Ostinata, in the second bed. On February 1, plant the third bed with a heat-resistant loose-leaf called Oak Leaf and with All the Year Round, a slow-tobolt English butterhead. You'll begin to reap the benefits of your labor at the end of February and continue to harvest through midMay.

SEEDS AND SEEDLINGS: Whatever crops you choose to grow, quality seeds will offer the best beginning. I often select hybrids that are bred for greenhouse culture or for disease resistance. However, many open-pollinated varieties rival these more expensive competitors. Generally speaking, most of your leafy vegetables can be ordinary garden cultivars, but you should choose specialty varieties of European cucumbers, tomatoes, cauliflower, lettuce, primula, stock, and gerbera. (See "Seed Companies for Greenhouse Culture.")

When sowing seeds, read the package! Following the directions on such important cultural instructions as soil temperature, depth of planting, refrigeration, or light requirements can increase your crop's germination percentage. In general, lettuce, kale, Chinese greens, endive, chard, sweet peas, nasturtiums, and calendula prefer cool soils (60°-70°F).

Tomatoes, peppers, melons, European cucumbers, and most annual flowers require a warm soil (70°-80°F). Poor seed germination usually is a result of improper or inconsistent soil temperatures. A propagating mat, which provides a constant soil temperature, will speed up seed germination and reduce losses due to damping-off. Made of heating cables sandwiched between vinyl coatings and regulated by a thermostat, it's a costly investment (about $110), but it's truly worth every cent. (A simpler method of providing constant bottom heat is to rest the seeded trays or packs on top of your refrigerator.)

A few vegetable favorites for cool greenhouses are described brief ly below. Southern growers, however, may have a wide; selection to choose from and more flexibility in planting times.

Lettuce, both loose-leaf and butterhead varieties, can be grown indoors from August through May, but true iceberg lettuce is strictly an outdoor crop. Lettuce varieties that have been bred for forced culture perform the best in winter months. Around the winter solstice, growth rate may be slow (regardless of variety), especially if soil temperatures drop below 55°F. The plants need proper spacing to reduce any problems with botrytis. The red-tipped varieties such as Merveille des Quatre Saisons, Ruby, and Prizehead will put color pizzazz in your salad.

Endive is a calcium-rich green that's related to chicory. Its flavor is bitter, compared with mild lettuce, so—two weeks before harvest—blanch the lower section to sweeten its taste. Endive often bolts by early February and should be used as a fall and winter green.

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