summer squash plant care and harvest tips
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Summer squash plants are famous for their high yields. Zucchini, yellow crookneck, patty pan, cocozelle and other popular summer squash varieties produce incredible quantities of fruits from early summer into fall. To ensure these high yields, and get the best quality squash, you will need to give them just a little bit of attention.

Planting Summer Squash

Plant summer squash in late spring or early summer, well beyond the last frost date. Summer squash seeds germinate best when the soil temperature is above 70 degrees Fahrenheit. Sow seeds directly into the garden, or start the seeds indoors two or three weeks ahead of planting time. Avoid transplant shock by exposing the seedling gradually to outdoor conditions before planting them into the garden.


Growing Summer Squash

Summer squash plants grow best in full sun, at least least six hours per day. They prefer moist, well drained, slightly acidic soil with a pH of 5.8 to 6.8. Squash plants tend to sprawl as they grow, so they need plenty of space. Plant seeds two to three feet apart between plants and four to five feet between rows. When watering, try not to wet the foliage. Instead, water at the base of the plant. Excessive moisture on the foliage can lead to fungal diseases.

Squash plants attract several types of pests. Covering your squash plants with row covers before they flower can help prevent these pests from laying eggs on your plants. When flowering begins remove the row covers. Pollinators need access to the flowers to make the plants set fruit. Avoid spraying harsh chemicals that can kill pollinators. To attract more pollinators into your garden, plant flowering annuals like marigolds and zinnias among vegetable plants.

Summer Squash Pests and Diseases

Summer squash is fairly carefree regarding diseases, but proper plant selection and growing conditions are key. Read seed packets and plant labels, and choose squash cultivars that are resistant to diseases. Space the plants out to allow good air circulation through the foliage as they grow. Keep the squash patch weed free.

Powdery Mildew


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POWDERY MILDEW: this week’s #sciencesaturday covers a very common problem that usually starts showing up in home gardens mid to late summer. PM (powdery mildew) is a fungal disease that affects many plants species. If you grow cucurbits (cucumbers, squash, zucchini, pumpkins) then you’re probably all too familiar with it. It looks like someone dusted flour on your plant foliage. White/gray spots appear on leaves and stems. Plants can handle some PM but as it spreads and covers more leaf surface, the plants’ ability to photosynthesize and grow is compromised. Leaves also get kind of gross and unattractive. Cause: Spores overwinter in plant debris and then begin to multiply in the spring. The spores are carried around by wind. PM thrives in hot and dry conditions which is not what you’d expect with fungal issues. Management: – Trim badly affected leaves and dispose. Do not compost! – Start a fungicide regiment. Copper or sulphur based products that are certified organic will help. – Neem oil is a natural and organic fungicide and can be applied. – Experiment with homemade solutions. Some people use baking soda and milk. Your mileage may vary. – Don’t overcrowd your plants. Give them room if you can. – Succession planting. Start some extra seedlings so that you can replace dying plants with new ones. I usually have 2 succession plantings of summer squash for this reason. – In the fall, make sure to dispose of all plant matter that was affected with PM. #powderymildew

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Powdery mildew is a fungal disease that can develop on summer squash during hot, humid weather. It appears as a white powdery coating on leaf surfaces. If an infection begins, treat it with a fungicide such as neem oil.

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Some of summer squashes’ common insect pests include squash vine borers, squash bugs, cucumber beetles. These bugs can stunt or kill your plants, so monitor your garden closely and treat for pests before their populations explode.

Squash Vine Borers


Squash vine borers are the larval stage of a black and orange clear winged moth. Watch for the moths hovering around squash plants in late spring and early summer. The moth lays eggs near the base of the plant. When the eggs hatch, the tiny grubs bore into the succulent stems of the plant, where they continue to eat and grow.

At first the plant may simply wilt in midday heat. If you look closely at the stem, near ground level, you’ll see a small entrance hole with greenish “frass” or grub excrement  around it. The stem around the entrance hole will likely feel mushy.

Left alone the borers will kill your squash plant. According to the University of Maryland Extension Service, gardeners can control borers as follows. “For active borers, make a vertical slit upward from where frass is observed. Use a razor or sharp knife and cut half-way through the stem. Remove and kill the borer. Mound soil over the wound to induce supplemental rooting.”

Growing techniques can help reduce the pressure of squash vine borers. One method is to use transplants instead of seeds. The mature stems are tougher for young borers to enter. Protect young squash plants with row covers until flowering, keep out the egg laying adults. Also, delay planting by four to six weeks to avoid the initial emergence of egg laying adults.

Squash Bugs


Squash bugs are very similar in appearance to stink bugs. Adults overwinter in the soil, and emerge in early summer to lay eggs on squash plant leaves. During the gardening season, adults stay hidden near the base of the plant while nymphs congregate on lower leaf surfaces. Both adults and nymphs feed on leaves and stems of the plants, leading to a stippled look. Advanced infestations may cause total leaf yellowing and significant reduction in fruiting.

Nymphs have soft bodies that are susceptible to organic insecticides like insecticidal soap and neem oil. Spray the product directly on the nymphs. Garden safe insecticides do not kill adult squash bugs. Instead, trap adults by placing a piece of cardboard beneath each squash plant. Squash bugs will hide there overnight. Check early in the morning and smash any squash bugs you find.

Cucumber Beetles


Striped cucumber beetles and spotted cucumber beetles are similar in size to ladybugs, but the body shape is more elongated. Cucumber beetles are yellow, with either black spots or black stripes that run the length of the body. They damage summer squash plants by chewing on roots, stems, and fruits. They are also carriers of bacteria that cause wilt disease.

Avoid infestation by delaying planting until later in the season, after overwintering adults have emerged and left the area. Use floating row covers to protect the plants until flowering.

How to Harvest Summer Squash

Sautéed Zucchini

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Summer squash are prolific producers, so get ready. When fruits begin to ripen, it is important to pick them frequently so that the plant continues to produce. Fruits mature quickly, so you will need to check the plants every couple of days. For the best flavor and quality, harvest young fruits before the seeds mature. Giant squash may win blue ribbons for an impressive appearance, but smaller squash tastes much better (and has thinner skin).

See our zucchini recipes and other summer squash recipes for ideas on how to use it all. Don’t forget to cook the blossoms too; try them stuffed and fried, or in tacos.

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