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I would like to plant vegetables in containers this winter. What can you tell me about indoor gardening?

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Growing vegetables in containers can be both fun and challenging. Surprisingly, most vegetables do very well in containers, but it is important to pay attention to light, temperature, soil media, rooting space, plant selection, watering, feeding and pests. Most gardeners grow plants in containers if they do not have enough space for a regular garden. Plants in containers can be grown indoors, on a patio, deck, terrace or balcony. They can be grown in window boxes, walkways, hanging baskets or other places that receive proper light. Consider the following information for successful container gardening.

Lighting. Adequate lighting is critical. Generally it is recommended that vegetables get a minimum of six hours of full sunlight. This is not a problem during the summer, but when growing them indoors in the winter, supplemental light is needed. Purchase and use grow lights, especially for vegetables that produce fruit, such as tomatoes.

Temperature regulation. Tomatoes and other fruiting vegetables require temperatures near 80 F during the day and 65 F at night. This ensures good fruit set. These temperatures are warmer than most home settings. At cooler temperatures, plants grow less vigorously and fruit size and number is compromised. Leafy vegetables such as lettuce grow better at cooler temperatures and are generally easier to grow.

Pollination. Be aware that indoor gardening can create pollination problems. Tomatoes set fruit best if the flowers are vibrated when they open. Some cucumber varieties may need to be physically cross pollinated since the plants produce separate male and female flowers on the plant.

Potting mix. Purchase a potting mix that drains well enough to avoid root rot but also holds enough moisture to supply the plant’s water needs. If you prefer to use garden soil, it must be sterilized. Once free of soil pathogens, it will need to be mixed with sand or pumice, organic matter or peat moss, then tested for pH. Homemade mixtures tend to be heavy when wet. There are many good “soilless” commercial potting mixes that work very well and are not expensive.

Container size. The smallest pot size to consider for indoor gardening is eight inches in diameter and eight inches deep. This works well for lettuce, radishes, onions or herbs. A large plant, such as a tomato or cucumber, will require a much larger container to allow for ample root development. Make sure the container has sufficient drainage holes to avoid root rot. Large containers to consider are half barrels, tubs, constructed wooden boxes or any other material that will hold the soil. Remember to consider the size and weight of the pot. This becomes important if you intend to start your plants indoors and then want to move them outdoors. Remember also that plants can be moved back in the house in the fall. Be sure to place a dish under the container so excess water does not ruin carpets or wood floors.

Seeds or transplants. You can start your pots using either seeds or transplants. When using seeds, over-plant the pots and thin later to get the desired number of plants per container. Be sure to allow plenty of space so the plant can grow without crowding. If you want to use transplants, either grow them or wait until the local nursery or garden center begins to stock them. Sometimes it is easier to start new plants in late summer for your fall indoors vegetable garden.

Water. Proper watering is critical for successful container gardening. It is easy to over-water and cause root rot. At the same time, if you leave for a few days, plants can wilt severely or die. It is difficult to recommend water quantity and frequency. A good rule of thumb is to apply water when the soil is dry about one inch below the media surface. In the heat of summer it may be necessary to water more than once a day. Water needs are generally proportional to the size of the plants.

Fertilizer. In addition to watering, container plants need to be fertilized regularly with a complete fertilizer mix. Since there are virtually no nutrients in “soilless” mixes, be sure the fertilizer you choose has all the essential nutrients needed for growth. Most container gardeners use a liquid fertilizer at a quarter to half strength every time they water. Be sure to follow the directions on the fertilizer package to ensure the plant gets necessary nutrients for proper growth.

Pests and disease. Aphids, fungus gnats, white flies and plant diseases can be a problem in containers. If you start with disease and insect-free plants, you are less likely to have pest problems. Since containers are isolated from each other, the spread of these problems is also minimized. Diseases can become a problem if you don’t water carefully.

Plant height and growth habit. When selecting vegetables to grow, remember to consider plant height and growth habit. Tomatoes and cucumbers will need support and can grow very large. Look for plants with a compact growth habit and those that mature rapidly.

While there is a lot to consider when gardening in containers, the reward is the freshest of vegetables, even during the winter. Containers also lend themselves to smaller gardens and patios, thus allowing food production in urban settings.

Posted on 7 Jan 2005

Dan Drost
Vegetable Specialist

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