Container Gardening

Information on container selection, media, plants, and culture for container gardening.

container gardening

herbs in pots

Lack of garden space does not have to limit your ability to grow flowers or vegetables. One option for individuals without much ground space may be “container” gardening, or growing vegetables and flowering plants in vessels of various sizes, shapes, and forms. Growing plants in containers provides gardening opportunities almost anywhere: on the patio, deck, porch, balconies, windowsills, or even inside under lights. Combining light-weight media, containers and some of the many cultivars of dwarf or bush vegetables and flowers allows those with limited space to grow productive and attractive gardens.

Advantages and Disadvantages

Container gardening has many advantages. A balcony or deck is always more inviting with a few plants on it. If you garden with containers, you can take your garden along if you move. Plants in containers can be arranged in different ways to take advantage of colors, textures, and times of bloom. If the container garden is close to the kitchen, it becomes a handy spot for culinary herbs.

In addition to producing food, the attractive foliage and colorful fruit of many vegetables has ornamental value as well. Small containers, or those with wheels, can be moved as necessary to more favorable environments with seasonal changes. When not in use, containers can be stored out of sight in the garage or basement.
Soil mixes for containers are often light and easy to work with. Older gardeners appreciate the “no-bend-over” gardening that raised containers provide, and containers can bring gardening closer to their house or apartment. Finally, planting a pot of lettuce, radishes, or flowers is an excellent way to introduce children to gardening.

The weather can make container gardening challenging. Extreme summer heat, coupled with high winds, can quickly dry the relatively small root zone area of container plants. This drawback can be minimized by careful selection of plants, media, site selection and watering methods. Water-holding polymers have been developed and can serve as a form of insurance against hot, dry winds. The polymers absorb many times their weight in water and release it to the plant roots as needed. These water-holding gels do not actually save water, nor are they a cure for poor care and neglect; however, they can serve to keep your plants alive when you cannot water during the hottest times of day.

Containers and Media

Containers are available in a variety of sizes and styles, from recycled buckets or tubs, laundry baskets lined with plastic, traditional clay or plastic pots, whiskey barrels, hanging baskets, tires, or traditional wooden planters. Plastic containers are lightweight and easily moved, and many window boxes are now available with trays. Clay pots are heavier and the soil ball will dry faster in clay pots than in plastic ones because water evaporates through the sides.

Wooden containers can be custom-made, but choose materials carefully. Avoid using wood treated with creosote or penta (Pentachlorophenol), as their vapors can injure some plants. Pressure treated CCA (chromated copper arsenate) wood can also be used for containers. Proper treatment procedures developed and monitored by the American Wood Preservers Bureau should allow this material to be used without any fear of leaching of chemicals. Research has shown that very little, if any, chemical movement occurs after treatment. Look for “Foundation” grade wood which is required to be redried after treatment with the waterborne wood preservative.

If you have reservations about using CCA-treated wood, consider using cedar or redwood for plant containers or other structures in the garden. Redwood and cedar are more expensive but resist rotting and do not require staining or painting.

The size of the container you use should depend on the eventual size of the plants it will contain. Larger plants, such as tomatoes, squash, or peppers, need 3- to 5-gallon containers. Smaller flowers and herbs, or vegetables such as lettuce, require pots or containers that hold 1/2 to 1 gallon of soil. Remember, the size of the container affects the eventual size of the plant and how often you must water and fertilize. Whatever container you use, be sure it has holes in the bottom to allow excess water to drain out.

Raised beds are another form of container gardening. The type of raised bed varies from one built up 6-8 inches to improve drainage to one high enough to work at while standing or sitting. Raised beds can bring the garden to a height that is more usable for people who cannot stoop or bend over to a flat garden bed.

Attaching wheels or casters to large containers will allow you to easily move the containers around to take advantage of changing light conditions. Wheels also allow easy mobility for winter storage.

Soil Mix

A well-aerated, well-drained, light-weight medium is best for growing plants in containers. The soil medium must support the plants and provide water and nutrients. Generally, it is not a good idea to use plain garden soil for container plants. The regular watering required by container plants causes garden soil to compact. Garden soil also dries out faster and is heavier than media you can purchase or mix yourself. These mixes are also less likely to contain weed seeds or disease organisms.

Most purchased or homemade mixes contain two or more of these ingredients: peat or other organic matter such as compost, rotted manure, or pine bark; perlite, vermiculite, soil, and sand. Organic matter holds water; the more organic matter in a mix, the less often you’ll need to water. Perlite and vermiculite keep mixes light and provide large pore spaces for good drainage. Sand of uniform particle size and free of silt also provides
drainage. It adds weight to a soil mix, so use sand in mixes for containers in windy sites or in those that won’t be moved often. Soil provides some micronutrients; a small amount should be added to media in which plants will be growing for longer than four months.

You can mix your own all-purpose media by using one of the recipes below.

Medium #1

Mix and moisten:

1 part sphagnum peat moss or composted bark or compost
1 part vermiculite
1 part sand

Medium #2

Mix and moisten:

1 part peat moss or composted bark or compost
1 part vermiculite or perlite
1 part top soil

Commercial mixes are also available under the trade names Promix, Jiffy Mix, Jiffy Pro, and others. “Bargain” soil mixes may need to be improved by adding additional perlite to improve aeration and drainage.

Plant Selection

Choose plants that are adapted to the site (sun or shade) and that are pleasing in form and color. Vegetables which produce fruit, such as tomatoes, peppers, beans, etc., require at least six hours of full sun to be productive. Leaf and root vegetables can get by with fewer hours of direct sun. Flowers should also be selected according to the amount of sunlight they will receive.

Small or low-growing flowers and vegetables are best for container gardening. These might include vegetables such as lettuce, beets, chard, or dwarf peppers, and flowers such as “cascade” petunias and dwarf impatiens. Herbs grow very well in containers and can be moved inside for winter to provide fresh seasonings.

If you want to grow larger vegetables such as squash or tomatoes, choose “bush” or “determinate” types that stay shorter in size, but still yield well.

Culture

Because container plants have root systems restricted by the container, culture and maintenance for these plants differ from that for plants in ground beds. Container plants must be fertilized and watered more often than garden plants. When making your soil mix, incorporate fertilizer into the medium at a rate of 1/4 cup of 5-10-5 or 10-10-10 per bushel before you fill the containers. Apply fertilizer to growing plants every 10 to 14 days by using a water-soluble mix of 10-10-10 or 20-20-20 at 3 tablespoons to 1 gallon of water, or use 1/2 to 1/4 strength water-soluble fertilizer at every other watering. Water thoroughly to prevent the build up of soluble salts.

Container-grown plants require regular watering.

In hot weather when plants are growing rapidly, you may have to water more than once a day. Avoid water-stressing plants, or otherwise spider mites will become a problem. You can minimize watering by choosing a medium high in organic matter and by using larger containers. Placing pots in sites where they will be shaded from the sun for a few hours in the afternoon and where they will be sheltered from hot winds will also help reduce the need for water. Use a mulch, such as dried grass clippings, around established plants to cover soil and reduce evaporation. You may want to experiment with some of the water-holding polymers. Finally, for large systems of raised beds or containers, you may consider installing drip irrigation to simplify watering.

Container-grown plants can be afflicted by the same insects and diseases as plants in the garden. Check the plants regularly and be ready to control these problems if they occur. However, pasteurized soil mix will eliminate most weed problems and many soil borne diseases.

Container gardening allows gardening where space is limited and lets you bring the beauty of flowers and vegetables closer to your home. For success, choose containers, soil mix, and plants with care, and remember the cultural requirements of this method of growing.

General Care

Vegetables grown in containers can be attacked by the various types of insects and diseases that are common to any vegetable garden. Plants should be periodically inspected for the presence of foliage-feeding and fruit-feeding insects as well as the occurrence of diseases. Protect plants from very high heat caused by light reflection from pavement. Move them to a cool spot or shade them during the hottest part of the day. Plants should be moved to a sheltered location during severe rain, hail, or wind storms, and for protection from early or late frosts.

Indoor Container Gardening with Vegetables

If you want fresh, home-grown vegetables over the winter, or if you don’t have an outdoor space in which you can place containers, it is worth trying some indoor container gardening. Of course you cannot have a full garden in the house, but a bright, sunny window can be the site for growing fresh food all year. Some small-fruited tomatoes and peppers, several types of lettuce, radishes, and many herbs are among the plants you can include in the indoor garden.

Follow directions given above for preparing pots and for watering, fertilizing, etc. However, note that plants will dry out less quickly indoors and will also grow more slowly, needing less fertilizer. To make watering easy it is wise to set the pots in large trays with an inch or two of decorative stones in them. Not only will this prevent your having to move the plants in order to water them, which may discourage you from watering when you should, but it will also provide humidity, which is a major requirement, especially during winter when the house is warm and dry.

As mentioned before, a sunny window, preferably south-facing, is almost a must for indoor vegetable growing.
Fruiting vegetables such as tomatoes and peppers will also need supplemental light, such as a combination warm-white/cool-white fluorescent fixture, during winter months. Insufficient light will result in tall, spindly plants and failure to flower and set fruit.

Herbs are a first choice for many indoor gardeners. Many are less demanding than vegetable plants, and cooks find it pleasant to be able to snip off a few sprigs of fresh parsley or chop some chives from the windowsill herb garden. Chives grow like small onions with leaves about 6 inches tall. These plants prefer cool conditions with good light, but will grow quite well on a windowsill in the kitchen. One or two pots of chives will provide leaves for seasoning salads and soups. Plant seeds in a 6-inch pot. The plants should be about 1 inch apart over the entire surface area. It will require about 12 weeks from the time seeds are planted until leaves can be cut. For variety, try garlic or Chinese chives, which grow in a similar fashion, but have a mild garlic flavor.

Parsley seeds can be planted directly into 6-inch pots, or young, healthy plants can be transplanted from the garden. One vigorous plant per pot is enough. Standard parsley develops attractive, green, curly leaves about 6 or 8 inches tall. Italian, or flat-leaved, parsley has a slightly stronger flavor and is a favorite for pasta dishes. Leaves can be clipped about 10 to 12 weeks after planting the seeds.

Cilantro, or the leaves of the young coriander plant,can be grown in the windowsill garden. Cilantro is used in Oriental and Mexican dishes, but it is not available in most grocery stores and must be used fresh. Grow cilantro as you would parsley. Thyme and other herbs will also grow well indoors if given the right conditions.

The small-fruited varieties of tomatoes such as Tiny Tim, Small Fry, and the paste tomato, Roma, may be raised quite satisfactorily in the home. They will challenge your gardening ability, and supply fruits which can be eaten whole, cooked, or served with salad. The Tiny Tim tomato grows to a height of about 12 to 15 inches. Small Fry, which is about 3 feet tall, and Roma will need more space and should be located on an enclosed porch or in a sun room. Several varieties have been developed for hanging baskets; they may be worth experimenting with.

Some of the small-fruited peppers may be grown as indoor plants. Like tomatoes, they require warm, bright conditions in order to grow well indoors. Fruits will be ready to harvest from peppers and tomatoes about ten weeks after planting. Whiteflies and aphids may present a problem on indoor tomato and pepper plants. Keep a close watch for these pests so they do not get a good start in your planting. Yellow sticky traps, either purchased or homemade, are effective in trapping white flies. Insecticidal soap or other pesticide approved for vegetable plantscan be used to control aphids. Fortunately, you will be less likely to experience problems with such outdoor pests as tomato hornworms, corn earworm (in peppers), and late blight than you
would if plants were outside.

For a quick-growing crop, try radishes. These must be grown very rapidly if they are to be crisp and succulent. Scatter radish seeds on moist soil in a 6-inch pot. Cover with 1/4 inch ofsoil and place a piece of glass or plastic wrap over the pot to conserve moisture until the seeds germinate. Carrots are slower, but can be grown in the same way; use the small-rooted varieties, such as Little Finger, for best results indoors.

Experiment with various types of lettuce. Leaf lettuceand the miniature Tom Thumb butterhead are some to try. Space them according to package directions. Keep lettuce moist and in a very sunny spot.

If light is limited, an old standby for fresh taste and high food value is sprouted seeds. Almost any seeds can be sprouted: corn, barley, alfalfa, lentils, soybeans, rye, peas, radish, mung beans, sunflowers, etc. Use only special seeds for sprouting available from health food or grocery stores to avoid the possibility of getting seeds treated with pesticide. Use any wide-mouthed container such as a Mason or mayonnaise jar. Soak
seeds overnight, drain, and place in the container. Cover with a double cheesecloth layer held with rubber bands, or a sprouting lid. Set the container in a consistently warm spot and rinse and drain seeds two or three times daily. In 3 to 5 days, sprouts will be 1 to 3 inches long and ready for harvesting.

Help for Growing Vegetables in Containers

Vegetable* Light
Requirements
**
Minimum container size Inches between plants in containers Days from seed to harvest Comments
Beans, Bush FS 2 gal. 2 – 3 45 – 60 Several plantings, 2-week intervals
Beets FS/PS 1/2 gal. 2 – 3 50 – 60 Thin plants when 6 – 8" tall
Carrots FS/PS 1 qt. 2 – 3 65 – 80 Several plantings, 2-week intervals
Cabbage FS/PS 5 gal. 12 – 18 65 – 120 Requires fertile soil
Chard, Swiss FS/PS 1/2 gal. 4 – 6 30 – 40 Harvest leaves
Cucumbers FS 5 gal. 14 – 18 70 – 80 Requires hot weather, Support vining types
Eggplant FS 5 gal. 1 / container 75 – 100 Requires fertile soil
Kale FS/PS 5 gal. 10 – 15 55 – 65 Harvest leaves
Lettuce, Leaf PS 1/2 gal. 4 – 5 35 – 40 Several plantings, 2-week intervals
Mustard Greens PS 1/2 gal. 4 – 5 35 – 40 Several plantings, 2-week intervals
Onions, Green FS/PS 1/2 gal. 2 – 3 70 – 100 Needs lots of moisture
Peppers, Bell FS 2 gal. 1 / container 110 – 120 Requires hot weather
Squash, Summer FS 5 gal. 1 / container 50 – 60 Plant only bush type
Tomatoes FS 5 gal. 1 / container 55 – 100 Stake & prune or cage
Tomatoes, Cherry FS 1 gal. 1 / container 55 – 100 Helps to stake & prune
Turnips FS/PS 3 gal. 2 – 3 30 – 60 Harvest leaves & roots

* Consult seed catalogs for varieties adapted to container culture.
** FS = Full Sun
FS/PS = Full Sun, tolerates Partial Shade
PS = Partial Shade