THINNING VEGETABLES
by Jerry Parsons, Ph.D.
Horticulture Specialist, Texas Agricultural Extension Service in San Antonio

Thin is in! Everyone wants to be thin or thinner. Vegetables are no different - they just need your help to accomplish the desired end results.

Vegetables will grow better when you thin them out. Conversely to their human counterparts, the thinner vegetable plants are, the larger they will become. This is not a contradiction because thinning refers to the number of plants in a given area rather than the size of an individual plant.

Plants require a certain amount of space for optimum root expansion and foliage growth if maximum production is expected. So, what about the Square Foot Gardening system, growing plants in containers, bonsai plants, etc.? All of these crowd plants and limit root systems. And all of these space saving techniques reduce yield potentials.

Remember the above statement, "plants require a certain amount of space for optimum root expansion and foliage growth if maximum production is expected." The key words to understand are "optimum" and "maximum" . Plants limited by space restrictions will produce, but not to the maximum. They will grow, but not in the optimum condition. This is true for those vegetables which need space to physically expand (the radish, turnip, onion bulb) as well as all vegetables which need the intensity of sunlight to energize the chlorophyll of cells to insure optimum functioning of plant processes and, consequently, maximum production.

Seed radish and turnips densely and the plants will immediately emerge and grow profusely. However, if some plants are not removed or "thinned", the radishes and turnips will never form the edible swellings (enlarged root) which we eat. How can the radish make a radish or the turnip make a turnip when they do not have enough room for physical expansion? Adequate spacing of plants is also important for the production of large onion bulbs. As with the radishes and turnips, don't expect to produce a 4-inch diameter onion bulb when plants are spaced 2 inches apart.

Crowded plants are also shaded plants. Closely spaced plants are actually destroying each other. Plant cells have energy generating systems activated by sunlight. No sunlight or reduced sunlight equals less energy, abnormal growth and limited production. Gardeners have been warned not to plant in areas that receive less than 8 hours of sunlight daily. Many of those gardeners who are fortunate enough to have a sunny location "shade" vegetables and limit production by planting large growing plants next to or in such a position as to shade smaller growing plants. When planting, always remember the ultimate size of the mature plant and the length of time that particular plant will be in the location. If the plant will shade adjoining plants, you must decide which vegetable is more desirous or rearrange the planting scheme.

Thinned vegetables are healthier vegetables. Vegetable diseases are communicable. Consequently close contact can be deadly to the entire community. Diseases are stimulated by the humid conditions caused by dense foliage growth of crowded plants. If a plant disease epidemic does occur, crowded plants prevent adequate curative spray coverage. Without such thorough spray coverage to protect against disease spore infestations, there is no hope for the salvation of the crop. Thinning must occur if a hygienically superior plant is to be expected.

Everyone knows that thinning is painful. It is difficult to remove those extra plants especially since you have worked so hard to grow them. Be brave!

To make the job less painful, try a periodic thinning process. For example, if snap beans are to be thinned to 4 inches between plants, thin the small plants until they are 2 inches apart. Then allow the remaining plants to grow for a period of time until they begin to crowd. At that stage, complete the thinning process so that plants are the recommended 4 inches apart. This system will avoid the necessity of replanting because you initially thinned your plants to 4 inches apart and a cutworm, dog, or bird thinned them to 8 or 12 inches apart!

When removing larger plants, use a knife to cut the stem at ground level. This will thin the plant population effectively and will not damage the root systems of the remaining vegetables as pulling out unnecessary plants would have.

Size of mature vegetables dictates the distance needed between plants. For instance, the larger growing vegetables such as broccoli, cabbage, cauliflower, cucumber, eggplant, cantaloupe, okra, squash, and tomato require 24 inches or more between plants. Smaller growing vegetables such as beans, beets, carrots, lettuce, onions, Southern peas, spinach, and turnips require only 2-4 inches between plants. Cultural techniques such as caging or staking also can influence how larger growing plants are spaced.

Thinning is just one of the "follow-through" activities which gardeners must do to insure gardening success. Others such as weed control, watering, insect and disease control, and properly timed harvesting will enable the early toils of garden preparation to pay off later in an abundance of fresh-tasting, nutritious vegetables for your family. But for now remember: "thin is in". Act now to give your plants plenty of those wide open spaces.