Conservatories and windowsills are good sites for growing vegetables. Put heavy containers on the floor or a firm support. Some vegetable plants, including trailing species, are suitable for growing in hanging baskets fitted with integral drip trays. Mushrooms are straightforward if you have space in a dark cupboard. Some plants such as chicory and rhubarb can be forced to produce their crop earlier than normal.
Tomatoes, peppers and eggplant: These easily raised tender crops are favorites for a sunny windowsill and can be grown from seed or small plantlets. For window boxes or hanging baskets, choose pendent varieties such as Tumbler tomatoes. Train cordon varieties such as Sweet Million tomatoes up canes or string in a conservatory, where they will produce long trusses of tasty, decorative tomatoes for several months. Peppers and aubergines are less prolific.
Carrots and radishes: Most root crops need greater depth than you can provide indoors, but radishes, especially round or globe varieties that do not root very deeply, grow well in boxes, troughs and pans. Seeds can be sown from late winter until mid-autumn, often producing usable roots 21 to 25 days later. Round carrot varieties are also successful in pots and boxes.
Potatoes: Seed tubers used for outdoor plantings are easily grown in large pots, buckets or even plastic sacks, and produce worthwhile yields of tasty new potatoes. When planting the tubers, leave space at the top of the container for adding more compost to earth up the plants as they develop. The top of the sack can be rolled down to start with, then rolled up, as required.
Mushrooms: Mushrooms are an ideal indoor crop for any time of year. Prepared bags of special compost with mushroom spawn only need watering before being left in a draft-free, dark place such as an attic or cupboard. Keep at 50 to 60ºF (10 to 15ºC) and mushrooms should be cropping a few weeks later. Alternatively make your own compost with straw and a purchased activator. Pack this mixture in a sterile container, such as a large plastic bucket. When the initial heat has died down and the mixture is turning into compost, add the spawn.
Beans and peas: Dwarf french beans can be sown in pots from late winter onwards for early pods. Dwarf broad beans and dwarf runner beans crop well indoors, too. Tall runner beans grown on cane wigwams or on string up the side of a sunny conservatory are decorative as well as productive, and both dwarf and tall mangetout peas will do well as houseplants. Pick the pods while they are young, tender and juicy.
Starting vegetable and flower seeds indoors is easy if these steps are followed.
The first step is seed selection. Make sure they are high-quality (purchased from a reputable seed dealer) and free from weed seeds. Hybrid seeds generally cost more than non-hybrid cultivars but may have increased vigor, better uniformity, larger yields, resistance to some diseases and other desirable qualities. If seeds from previous years are used, the germination percentage decreases. How much depends on how they were stored. If stored in a cool, dry location, many seeds will germinate to acceptable percentages for a couple years.
Sow seeds in any container, as long as it has proper drainage and does not contain toxic substances. Previously used containers need to be cleaned thoroughly with a disinfectant or soapy water. Use seed-starting kits or fill plastic, clay or peat containers with growing media. Desirable media is loose, fine in texture and drains well. Purchase commercial container/starter mixes or buy materials and mix yourself.
Sow seeds according to package directions; some may need to be covered with a thin layer of soil. The use of plastic over the top of the planting container retains moisture and humidity needed for germination. Keep seeds out of direct sunlight until they germinate. Days to germination varies with plant species. Time seeding of warm-season transplants to synchronize with when seedlings can be moved outdoors following last frost.
After seeds emerge, remove plastic cover and place near a bright window or under energy efficient grow lights. Keep the light as low to the seedlings as possible, to prevent stretching. Seedlings in soilless mixes need regular fertilization. Apply a water-soluble fertilizer at half-strength a week after seedlings germinate. Then fertilize every two weeks at full strength.
Transplant seedlings after they develop at least one set of true leaves (the leaves above the cotyledons or “seed leaves”). Transplant into individual pots or thin within the flat. Remove seedlings carefully to preserve as many roots as possible. Seedlings are fragile so avoid picking them up by the stem.
Approximately two weeks before planting outdoors, begin hardening off the fragile seedlings to increase their chance of survival. Place them outdoors where they will receive direct gradual sunlight. Start with a couple of hours of sun, then gradually increase and expose to some wind for a few hours each day for a week. Gradually lengthen the amount of time outside each day. Move the plants inside at night if temperatures drop to near freezing. Keep them watered and once the plants are hardened, transplant into the garden and enjoy the summer’s bounty!
ARS Landscape Materials & Supply, Denver, Colorado