Small vegetables–many leaf crops and even compact and miniature varieties of fruiting crops such as tomatoes and peppers–can be grown indoors on a sunny, bright windowsill year-round.
Vegetable gardening indoors has most of the same requirements as an outdoor garden: bright light, water, nutrients, and protection from pests and diseases. Since space is likely to be more limited growing crops indoors, choosing quick-maturing crops planted in quick succession is your best strategy; for example, sow a few seeds of leaf lettuce each week and harvest leaves often while they are still young and tender.
Tips for Growing an Indoor Vegetable Garden
Crops to grow indoors
Choose compact, miniature, or dwarf varieties of crops and crops that are quick maturing. Small, quick-growing crops will require less space and time to reach harvest.
You will have the best success growing indoor crops close to the natural season each crop grows outdoors. Cool-weather crops such as leaf crops and root crops are a good choice for the autumn and winter indoor garden; these crops naturally require less bright light. Warm-weather crops–fruiting vegetables such as tomatoes and peppers–require longer days to ripen, so planting these in spring and summer makes sense.
Autumn and winter crops include beet greens, chard, Asian greens, kale, lettuce, mustard, and other leaf crops. Other cool-weather crops that can be grown indoors include carrots, cauliflower, peas, cabbage, and beets–if room allows. Herbs for cool temperatures include rue, sage, mint, marjoram, parsley, and chives.
Spring and summer crops include tomatoes, peppers, eggplants, bush beans, and most herbs. These crops require eight hours of sunshine or bright light and a room consistently warm.
Crops not suited to windowsill growing are tall and vining crops such as corn, pole beans, squash, melons, and pumpkins.
How to plant for indoor growing
Plant indoor crops in pots that will allow roots plenty of room to grow; a single lettuce plant can grow in a gallon pot, and a small tomato plant will require a 3 to 5-gallon container. A medium-texture potting mix will hold moisture, air, and nutrients better than a fine or coarse soil mix. Choose a commercial potting soil or use 2 parts garden soil, 2 parts finished compost, 1 part peat moss, and 1 part vermiculite or perlite.
Sow seeds just as you would in the garden and thin plants to the strongest seedling from two to three weeks after germination when seedlings have grown their first true leaves and have gained strength. Snip away the weakest seedlings at the soil level with small scissors.
If you plant more than one crop in a container, don’t plant them too close together or they will compete for light, water, and nutrients–resulting in weak plants all around.
Light for indoor growing
Growing vegetables indoors requires bright sunlight just like outdoors or bright artificial light. A south-facing bay window that gets light from the south, east, and west is an ideal place for a window garden. Windows that are not in the shadow of eves are best. Placing your indoor garden in a white or light-colored room will help as well; light colors reflect light; dark interior surfaces will absorb light.
If your growing space is dark, artificial light can take the place of sunlight–of course, you pay for electricity. Consider the wattage of grow lights and expense. Choose grow lights designed for plant growing (lights rich in the red and blue spectrums are needed by plants for photosynthesis).
If you don’t have much sunlight, grow salad greens and herbs that require less sunshine; but remember, they still require bright light.
Temperature for growing indoors
Summer crops grow best at temperatures between 75° and 85°F in the daytime and 60° and 75°F at night. Autumn and winter or cool-weather crops grow best at temperatures between 60° and 65°F in the daytime and around 50°F at night. Plant with warm roots can withstand air temperatures 5° to 10°F cooler than recommended; a heating pad made for plants can help. Good air circulation indoors will help keep plants healthy.
Watering plant indoors
Water indoor crops as needed; stick your finger in the soil and if it comes out dry water; if it is damp or wet don’t. Too much water can result in fungus disease. Water indoor crops in the morning on sunny days when possible; evaporation will be slowed on cloudy and cool days. Plants require less water in winter. Use room temperature water and avoid water softened with a commercial water softener.
Feeding plants indoors
Feed indoor, container-grown plants every other week. Compost tea, liquid fish emulsion, and liquid seaweed are rich organic liquid fertilizers. A foliar spray of compost tea or liquid seaweed will aid disease resistance. Fertilize less when temperatures are cool.
Plant pests and diseases indoors
Aphids, mites, and whiteflies can attack indoor vegetable crops. Give indoor growing plants a strong rinsing under the kitchen faucet every two weeks. Spray the entire plant with lukewarm water. Check the undersides of leaves to make sure bugs have been washed away. A foliar spray of dilute compost tea every couple of weeks will minimize most diseases.