Summer Squash

Summer squash (Cucurbita pepo) is a warm-season crop that can be planted from seed or transplants. In South Carolina, summer squash has two planting dates.
The spring planting dates are April 1-20th in our region and the fall planting dates are August 1-15th. Plant squash in full sun in rows spaced 3 feet apart. Plant seeds ? inch deep and 4 to 6 inches apart in the row. When the seedlings are in the one to two true-leaf stage, thin the plants to 12 to 15 inches apart by selecting the most vigorous ones. Squash transplants should be placed 15 inches apart at planting time. Squash can also be planted in hills. Rows should be 4 to 6 feet apart, with hills 3 to 4 feet apart within the row. Place two or three seeds in each hill.
Summer squash includes yellow (straight and crookneck), zucchini, and scallop. Some varieties have a bush-type of growth instead of the vining habit, which is useful in small gardens.
Recommended cultivars for South Carolina home gardens are:
• Yellow Straightneck – Early Prolific, Cosmos, Multipik, Saffron, Seneca Prolific, Slick Pik® YS 26, Superpik
• Yellow Crookneck – Destiny II, Dixie, Early Summer, Gentry, Gold Star, Golden Summer, Supersett, Yellow Crookneck, Zephyr Hybrid (a cross between a crookneck, delicata, and acorn squash)
• Zucchini – Black Beauty, Eight Ball, Elite, Embassy, Senator, Spineless Beauty
• Scallop – Early White Bush, Jaune et Verte, Peter Pan, Sunburst
A soils test is the best method of determining the fertilization needs of any crop. If you have not taken a soils test, start with a preplant application of 5-10-10 fertilizer at 3 pounds per 100 square feet. Sidedress before the vines start to develop using 34-0-0 at 1 pound per 100 feet of row or calcium nitrate (15.5-0-0) at 2 pounds per 100 feet of row. More frequent sidedressing may be required if the garden is sandy or if leaching rains occur. Do not overfertilize with nitrogen because this reduces fruit growth and encourages excess vine growth.
Light watering encourages shallow rooting of the plants. Deep, infrequent watering encourages roots to move to a deeper into the soil. Water the garden in the morning so the foliage is dry before dark. Try not to water the foliage, but instead water the roots. Preventing water on the foliage helps to prevent diseases from spreading.
Blossom-end rot is a common problem with summer squash. A dark-colored dry rot at the blossom end of the fruit is the main symptom. Blossom-end rot is caused by a lack of calcium in the developing fruit. Calcium may be lacking in the soil or the plant might not have the ability to take up adequate amounts of calcium from the soil. Do not overfertilize plants with nitrogen or potassium. Excessive amounts of these nutrients depress the uptake of calcium.
Squash have separate male and female flowers on the same plant. Bees must transfer pollen from the male flower to the female flower. Poor pollination can result in improperly shaped fruit. Use insecticides and fungicides late in the evenings to prevent the killing of bees and other pollinators.
Summer squash can be harvested in about 55 days after planting. Harvest fruits when they are tender and still have a glossy or shiny appearance. Harvest crookneck and straightneck varieties when fruit is 1? to 2 inches in diameter. Harvest zucchini when fruit is 7 to 8 inches long and scallop types when they are 3 to 4 inches in diameter. For extra tenderness, squash can be harvested at smaller sizes. Do not leave large fruit on the plant because this will inhibit the development of additional fruit. Summer squash can be stored in the refrigerator for up to 1 week.
Insect problems include spotted cucumber beetles, striped cucumber beetles, squash vine borers, aphids, squash bugs, and pickleworms. Aphids can transmit viruses to the plant. Squash vine borers can cause total collapse of the plant. Plant early because squash vine borers and pickleworms are problems later in the season. Squash vine borers can cause sudden wilting of a plant. The female lays tiny, cooper-colored eggs on the stem of plants.
As the eggs hatch, the larvae, which look like small white grubs with dark heads, burrow into the stems to feed. Inspect the stems of the plant for yellowish, sawdust-like material, which indicates a borer at work.
If a borer makes it into a stem, you don’t have much to lose so you might as well try to save the plant. Use a small knife to make a vertical (lengthwise) slice into the vine in order to remove and kill the larva. Place soil over the stem to encourage root development and keep the plant thoroughly watered.
For a list of examples of insecticides labeled for use in the home garden, visit HGIC Factsheet #2207, Cucumber, Squash, Melon, & Other Cucurbit Insect Pests (tables 1 and 2). Common disease problems include powdery mildew, anthracnose, downy mildew, gummy stem blight, and viruses.
For a list of examples of fungicides labeled for use in the home garden, visit HGIC Factsheet #2206, Cucumber, Squash, Melon, & Other Cucurbit Diseases (tables 2 and 3).
For more information on Summer Squash, please visit the Home and Garden Information Center website at
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