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
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.