A Good Potting Mix

When you garden in containers, you want a potting mix that is fast draining, yet provides enough water retention to keep the soil evenly moist in the root zone area. A mix that drains too fast won't provide enough moisture, and one that holds too much moisture may cause the roots to rot.

Most home gardeners who grow vegetables in containers find a "soilless" commercial potting mix works well. These mixes are easy to use, lightweight, fast-draining, and free from soil-borne diseases and weed seeds. Since they come in varying-sized bags, you can buy as much as you need at the time. The unused portion can be stored in its bag until you want to use it again.

If you choose to make your own mix, a good potting soil for containers consists of equal parts sharp sand (be sure to buy washed sand), good garden soil, and organic material (peat moss, leaf mold, fir bark, or sawdust). To be sure your homemade mix is free from disease and weeds, heat it in a low temperature oven for about 1 1/2 to 2 hours. This should kill any bacteria, pests, or weed seeds present.

Other good soilless potting mixes specially formulated for container gardening are the University of California mix and the Cornell mix. Information on each mix can be obtained by writing the University of California, Division of Agricultural Sciences, Berkeley, Calif. 94720, or to Cornell University, Department of Floriculture, Ithaca, N. Y. 14853.

Some commercial mixes are extremely lightweight. These are excellent to use in hanging baskets, in very large containers that you want to move around, or where sheer weight could be a problem, such as on a balcony or in a window box. An ultra-lightweight mix also has some disadvantages. If wind is a problem in your area, top-heavy containers may topple over. Top-heavy plants, such as corn, tomatoes, and eggplants, may not get enough soil support for their root systems.

If you find your commercial potting mix isn't absorbing water (the water runs through the container rapidly and many particles float on the surface without absorbing any moisture), try using a few drops of liquid detergent in the water. The detergent acts as a wetting agent. Or you can use a commercial wetting solution. Once these stubborn mixes begin to soak up water, your problem should be solved.

A soilless commercial mix contains few if any nutrients. Vegetables grown in these mixes will need regular fertilizing with a complete fertilizer formula.

Container vegetables have needs that differ from vegetables grown in the ground. Fertilizing, watering, general maintenance, and harvesting demand close daily attention and are crucial to the plant's well-being. Vegetables in containers are at the gardener's mercy.

Planting Techniques

Most vegetables grow as well from seed as from transplanted seedlings. However, if your containers will be conspicuous (on a balcony, patio, or in a window box), planting seedlings will give you an instant display. Some vegetables, such as tomatoes, peppers, eggplants, and squash, may be difficult to grow from seed. Using seedlings will speed up their growing process.

If you plant seeds in larger containers, you can still have attractive pots while the seeds are sprouting. Plant annual or herb seedlings as a border.

Limiting the number of plants to each container is very important. Estimate the number of plants a container can sustain. Measure root crops by the space they'll occupy when fully matured. Bush squash and vine crops such as melons and cucumbers should each have a good-sized space. Corn needs cross-pollination, so plant several stalks to each container.

Beans and tomatoes with indeterminate growth habits will need supports. Beans can climb up poles or a trellis. Tomatoes can be staked or enclosed in a wire cage.

Other vegetables can be grown singly or in groups, depending on the container size and eventual size of the plant at maturity.

To plant vegetables by seed, fill the container to within 1 inch of the rim with damp potting mix, then sow seeds according to their package directions. Be sure to plant more than You want, since it's unlikely you'll Get 100 per cent germination. When the seeds have sprouted and each seedling has mature leaves, thin the plants to the desired number.

To thin seedlings in a container, cut off the seedling's stem at the soil level with scissors, a knife, razor blade, or pruning shears. Pulling unwanted seedlings out may disturb or destroy surrounding root systems.

To plant vegetable seedlings, prepare the container as before. Remove the seedling carefully from its pot. (Seedlings grown in peat pots can be planted directly, pot and all. Break off the upper rim so the soil level is uniform.)

If the roots are tangled or pot-bound, loosen them with your fingers. Dig a small hole in the potting mix and plant the seedling. Try not to bury the plant stem or change the soil level. Tomato seedlings are an exception; you can bury tomato plants up to half the stem length as long as there are at least 2 sets of mature leaves above the soil.

To help transplanted seedlings establish themselves, use a transplant starter solution. Follow label directions.

Vining plants and vegetables, such as tomatoes, may need to be staked or trellised. Any support structure must be sturdy. Stakes, poles, and trellises should be set in place when the seedlings are little to avoid disturbing their root systems (wire cages used for tomatoes should be set up at this time too). Some wining plants, like pole beans, will attach themselves to the support. Others, like tomatoes or cucumbers, need to be tied. Use twine or plastic tape for tying; be sure not to tie stems too tightly or cut the stem. The most stable support systems are those attached to the container itself.

Watering

Watering is probably the most critical task a container gardener performs. More plants grown in containers fail from improper watering than from any other single cause. Plants given too much water may develop root rot. Vegetables that receive too little water may wilt and die. Improper watering can also cause blossoms to drop.

Ideally, potting mix in a container should be evenly moist throughout not waterlogged. Plants need ample moisture to prevent "water stress."

Many gardeners water containers in the morning, adding water until it comes out the drainage holes. This method is recommended only if your potting mix is fast-draining and the container has adequate drainage holes.

With watering in the morning, foliage should be dry by evening, helping prevent diseases. If you live in a hot, dry climate, check your containers again in the early afternoon. Vegetables in containers will dry out faster than those in the ground.

The best way to water container plants is by hand either with a hose that has a sprayer attachment or a watering can. More inventive gardeners may want to try automatic watering systems, but these can be costly.

A few words of warning: Hoses without a sprayer/mister nozzle can disperse water with enough force to create holes in the potting mix. This can damage root systems. Also, if hose sits in the sun, let enough water run through it until the water is cool or lukewarm. Hot water isn't good for plant roots.

Mulching and Fertilizing

Mulching, especially in larger containers, can help keep moisture in the soil longer. You can use any of the organic mulches, such as wood chips, compost, or sawdust, very effectively. Plastic mulches will work, but they aren't too attractive.

Vegetables grown in containers are trapped. Once they use the nutrients available in the potting mix, the root systems have nowhere else to go. Frequent and regular fertilizing is the answer.

The container gardener will find many kinds of complete fertilizers specially formulated for use on vegetables. Common N-P-K breakdowns are 18-20-16, 18-12-10, or 10-10-10. Fish emulsion is also commonly used.

These fertilizers can be applied in a liquid solution in conjunction with watering, scratched or duo, in dry form into the soil surface, or, in the case of timed-release fertilizers, sprinkled on the soil surface. Whichever type you choose, follow the label directions carefully.

Since containers with vegetables should be watered daily, nutrients can leach out of the soil rapidly. Consider applying fertilizer at half strength twice as often; this should assure your vegetables consistent fertilizer.

Timed-release fertilizers are also a good solution. Their capsules are constructed to release a tiny amount of fertilizer each time the vegetable is watered, and you only apply this type once a season.

Container gardeners are fortunate since each vegetable is isolated by its pot, and no one crop is concentrated, lessening the chance of a pest infestation. Unfortunately, pests can still present a problem. Most insects, such as whiteflies and aphids, can be discouraged with blasts of water. Tomato hornworms can be hand picked. Snails and slugs can be baited with a chemical.

If pest damage becomes intolerable or your crop is being damaged, use a spray formulated to kill the damaging pest. Be sure any chemical sprays you choose are recommended for use on vegetables.