With a bit of extra effort and some common sense, you can grow (almost) any vegetable in a container that would normally be planted in the ground (no, not corn!). See our Care Guide on Container Gardening for the pros and cons of the various materials used for containers; from terra cotta to plastic. It doesn’t make much difference which you choose so far as the plant is concerned. Unquestionably, the most economical will be a used black plastic nursery pot. Black pots absorb heat and are particularly suitable early in the growing season when the air and soil are still cold. During late July and August when we approach three digit temperatures, it would be wise to shield the pots with aluminum foil because soil temperatures over 85-90°F will damage plant roots.
The minimum container size is five gallons. A fifteen gallon container is more suitable and a half-wine barrel is excellent. Exceptions are for the herbs which will grow quite well in one gallon cans. A tray under your container is not a requirement except that if you water plants on a third floor balcony, the neighbors on the second floor may appreciate it!
A good quality potting soil such as Gardener’s Gold is an absolute requirement for successful container gardening. A good quality potting soil must have a minimum of six different ingredients (Gardener’s Gold has nine). Many ‘house brands’ sold by discount or hardware stores and labeled as potting soil are inferior products which should be avoided.
Under no circumstances should you use garden soil or homemade compost. Neither of these will provide proper drainage or aeration and there is the danger of introducing disease or insect pests into your container.
Vegetables which produce fruit such as Tomatoes, Squash, Pepper, String Beans and such need an absolute minimum of 6 hours of sun per day; 8 hours is optimum. With too few hours of sunlight, there may be many green leaves but no fruit. With this in mind, the Tomatoes and Peppers get the sunniest location and the Lettuce, Spinach, Cilantro, Basil and other leafy vegetables can be planted where there is less sunlight. Unfortunately, the perennial herbs (Rosemary, Thyme, etc.) are most flavorful when grown in the strongest sunlight.
Containerized plants often have to be watered more frequently than the same plants growing in garden soil. Small pots, dry out more quickly than larger pots, as do terracotta pots when compared to plastic pots. The larger the plant, the more quickly it uses up the water in its container. During hot weather, it would not be unusual to water containerized plants every day or every other day. Mixing hydrogel into your potting mix won’t diminish the amount of water used but it will extend the time between watering. When watering the containers, always water until it runs out the bottom of the container. If you have saucers under the containers, leave about one-half inch of water in the saucer for the pot to wick up.
Containerized vegetables grow in a space much smaller than normal. When growing the garden, vegetables need to be fertilized about twice a season. The same plants growing in a container will use up all the nutrients in a good potting soil with one or two months.
Consequently, vegetables need to be fertilized every month after the second month in the container. Pelletized fertilizers such as Master Nursery Tomato and Vegetable Food are preferred to those which you dissolve in water.
An example of a planting in a 15 gallon container would be: an Early Girl Tomato in the center surrounded by a five foot tomato cage and half a dozen Bibb Lettuce plants along the rim of the container. Another 15 gallon container could contain one Ambassador Zucchini or 8 Bush String Beans which are allowed to drape over the sides.
Containerized plants are as likely as garden grown plants to be beset by insects and diseases. The treatments used for garden plants can be applied to plants in containers.
Many fungicides and insecticides are available in ready to use spray bottles. Some, such as Safer Yard and Garden Insect Killer and Safer Garden Fungicide, have very low or no toxicity to humans and their pets.
Please also see these additional Care Guides for further information:
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