Keep your kitchen flooded with this summer staple vegateble

Story by Maureen Heffernan

Gardeners love to lament their overabundance of zucchini and other summer squash that flood their summer vegetable gardens. But I think most gardeners are actually thrilled to see the marvelous wealth they coaxed out of a small seed or tender transplant. 

These squash were grown from seed along with plantings of basil.

Summer squash (Cucurbita pepo) is just that – squash that need the warm summer weather to grow and fruit. Unlike winter squash – such as butternut – they can grow in smaller areas because of their compact, bushy forms. And unlike winter squash, summer squash do not harden nor can they be stored for long periods. In addition to being prolific, summer squash grows quickly – averaging 50-70 days to harvest after planting, depending upon variety. 

Summer squashes include: zucchini, most have green skin although some varieties are yellow; scallop or pattypan have a flattened shape with scalloped edges and can be green, white, yellow, or bicolor; straightneck and crookneck squash are longer with skin that can be smooth or bumpy. 

Summer squash needs a full-sun site with fertile, well-drained, moist soil with a pH between 6.0-6.8. Work several inches of compost into the soil to at least 12 inches to improve drainage and structure.  

Because summer squash does produce so abundantly, the rule of thumb is two or three plants should produce enough for four people, plus some to share. 

It’s easiest to direct-sow seeds one to two weeks after your area’s average last frost date. In Oklahoma, that is roughly late April to late May, or early June depending on where you are in the state. Because summer squash grows quickly, you can plant another round about six weeks later for nonstop summer squash. 

Sow seeds ½ inch deep and space seeds 3 feet apart within a row and space rows about 3 feet apart. You can sow two to three seeds in the general area where the plant is to grow. Seeds should germinate in less than a week. Once seedlings emerge and grow a few inches, select the strongest looking one to remain and pluck out others. Gently water in and make sure soil is kept moist during the germination period and as seedlings emerge and grow. 

For earlier yields, you can also start seeds indoors about four weeks before time to plant outside. Use peat pots that can be planted directly into the garden because squash plants don’t like their roots disturbed once they develop. 

When plants are about 4-6 inches tall, apply a balanced, organic fertilizer and then add an inch or so of compost. Summer squash plants are heavy feeders, so follow directions for regular feedings. As plants grow, add a layer of straw around and between the plants to help maintain soil moisture. Water well, at least once a week (or twice during hot, dry spells) to a depth of 1 inch during growing period.

While plants must be well watered, try not to wet the foliage to prevent disease problems. Drip or soaker hoses are recommended so that water is applied directly to the soil. Water in morning or afternoon; avoid watering in the evening because then the water won’t have enough time to dry off of the foliage.  

Squash plants must be pollinated in order to produce fruits. Bees and other insects pollinate female flowers with pollen from male flowers. Male blossoms appear first to supply the pollen, but do not develop fruit. Female blossoms appear a bit later to be pollinated by the carrying pollen from the male to the female flowers. If you look closely, you can differentiate male and female flowers. The stem of male flowers is thin, while the females are thicker at the base. Below the female petals, you will notice a bulge, which is the developing fruit. To increase pollination levels to set more fruit, use a small paintbrush to move pollen from the male blossoms and to the females. This tactic is useful especially when you have just a couple of plants. 

Left: This female squash bloom is open and waiting for pollen. Right: This is a male bloom on a squash plant. It will never make a fruit; its only purpose is to produce pollen to fertilize the female blooms. Photos by Mallory Kelley.

Squash vine borers and squash bugs are two of the most problematic pests of squash plants. One control method is covering the plants with row covers after they are several inches tall. Lightweight row covers allow light and air in but keep pests out. When plants start to bloom, covers can be removed so plants can be pollinated. 

Squash bugs are grayish brown and approximately ½ inch long. Squash bug nymphs and adults feed on the leaves, which causes them to wilt, blacken, and eventually die. 

Squash bugs (adult seen in larger image above) suck sap and carry disease; so close monitoring of plants for infestation is critical. Inset top: squash bug eggs. Inset bottom: squash bug nymphs. Photo by Kristi Cook.

The best control is frequent inspection. Remove the bugs and drop them in a bucket of warm soapy water. Look for dark reddish eggs on the undersides of leaves. If you see any, just rub them off. 

Squash vine borers are another headache. These look like white caterpillars and they bore into stems, causing them to eventually wilt. Frequently inspect base of plants for orange eggs. If you see any, as with the squash bug eggs, just rub them off with your fingers. You can apply Bt (Bacillus thuringiensis) around the stems. 

Squash vine borer larva

Common diseases of squash plants include:

• Downy mildew – One of the major leaf diseases of cucurbits; higher incidence in moist conditions. Initial symptoms are yellow spots on upper leaf surfaces and a gray mold may appear on the undersides. It can spread to other leaves causing leaves to die back. Fruit is not affected. Prevention and/or treatment: Planting resistant varieties is the best control method. If the disease is severe enough to require chemical control, there are approved fungicides available for the home gardener. As always, read and follow all labeled instructions.

• Powdery mildew – Whitish powdery growth on upper foliage surface; fruit usually not directly affected, but may be stunted. Prevention and/or treatment: Planting resistant varieties is the best control method, making chemical control not usually necessary.

• Bacterial wilt – A disease that causes plants to suddenly wilt and die; not as prevalent in squash as other cucurbit plants. Prevention and/or treatment: No chemical control available; regularly inspect plants. Insecticides that control striped and spotted cucumber beetles in the home vegetable garden include carbaryl, bifenthrin, cyhalothrin, or cyfluthrin. Because bees pollinate squash, if chemical treatment is necessary, apply late in the afternoon according to directions on the label.

• Anthracnose – Caused by a fungus that usually appears after several days of rainy cool weather. It first appears as yellowish spots on leaves that eventually enlarge and turn brown or black. Infected fruits have black, circular, sunken cankers of different sizes. Prevention and/or treatment: Remove and destroy affected plants; crop rotation.

• Cucumber mosaic virus – This viral disease causes stunted growth, wrinkled leaves, and fruit that may be irregularly shaped, mottled, or warty. It is spread by various insects. Prevention and/or treatment: regular monitoring of plants, maintaining healthy plants, keeping the garden free of weeds.

Other preventive measures include frequently inspecting plants; ensuring adequate air circulation around and between plants; avoiding overhead watering, especially in the evening; practicing crop rotation; selecting disease-resistant varieties; and keeping planting areas clean of old debris to prevent providing places for pests to overwinter.*

Bigger is not better with summer squash. For the best taste and texture, pick while the fruit is young and the skin is thin and soft. Zucchini and crookneck squashes can be picked at about 6-8 inches. Pick round types at about 4-8 inches in diameter. By picking fruit while still young, plants will continue to produce. 

Carefully break off stem or use a sharp knife, leaving a bit of the stem on the fruit. You will need to harvest several times a week as fruits reach harvestable size. Since they don’t store well, use or share them soon after harvesting. 

Summer squash can be sautéed, grilled, fried, stir-fried, or steamed. They are delicious in casseroles or other recipes that pair them with tomatoes and onions. Zucchini bread is especially delicious. 

*Doubrava, Nancy, James H. Blake, Anthony P. Keinath, and Joey Williamson. “Cucumber, Squash, Melon & Other Cucurbit Diseases.” HGIC 2206 Cucumber, Squash, Melon & Other Cucurbit Diseases: Extension: Clemson University: South Carolina. November 2017. Accessed February 19, 2018. http://www.clemson.edu/extension/hgic/pests/plant_pests/veg_fruit/hgic2206.html.




Recommended Summer Squash Varieties:
Zucchini: ‘Butterstick’, ‘Burpee Hybrid’, ‘Costata Romanesco’, ‘Eight Ball’, ‘Onyx’, ‘Senator’, ‘Elite’
Crookneck: ‘Sun Drops’, ‘Early Golden Crookneck’, ‘Pic-N-Pic’, ‘Dixie’, ‘Paro’, ‘Tara’
Straightneck: ‘Goldbar’, ‘Early Prolific Straightneck’, ‘Multipik’, ‘Lemon Drop’
Scallop or pattypan: ‘Benning’s Green Tint’, ‘Early White Bush Scallop’, ‘Peter Pan’, Burpee’s Summer Scallop Hybrid mix, ‘Sunburst’

Scroll to Top