Pattypan, crookneck, straightneck and zucchini — these are the summer squashes, all highly productive, a pleasure to grow and better to eat. What sets summer squash apart from winter squash is that the fruit are soft-skinned, tender and intended for eating right away. They are picked while immature and lack the tough skin that makes winter squash suitable for months-long storage. If you want to grow summer squash in your garden, here’s everything you need to know.
You can also download my How Do I Grow Summer Squash one-sheet and keep the free resource handy for your reference.
Summer squash are cultivars of the species Cucurbita pepo, the same species as most pumpkins and a number of other winter squashes. The fruit of summer squash plants are usually green, yellow or both and come in a number of shapes depending on the variety. They can be sliced up to be roasted, sauteed, baked or grilled, and can also be spiralized to replace pasta. Zucchini can even be shredded and added to pancake batter, or thin sliced and used as a pizza topping.
Where, Where and How to Plant Summer Squash
As the name hints, summer squash is a heat-loving plant. Refrain from planting outdoors until the soil temperature has risen to 70°.
Summer squash may be direct-sown, but you can give plants a leg up by starting the seeds indoors three to four weeks before the last frost date for your area. Plant seeds 1 inch deep, with two seeds per pot, in sterile seed starting mix that’s kept between 70° and 95° with a seedling heat mat. The seeds will germinate 7–10 days later. Thin to one seedling per pot.
Use a grow light to ensure seedlings get the light they require. If the seedlings are grown far from a lamp, they will stretch out to find the sun. Run a fan gently over the seedlings to prevent damping off disease.
Before seedlings can be planted outdoors, they must be hardened off. Hardening off is the process of gradually introducing plants to the outdoor environment and the intensity of the sun. Put seedlings out for just a half hour on the first day and add more time outdoors each day for a week until they are ready to handle eight hours of direct sunlight.
Summer squash cultivars are bush-type plants, unlike many winter squash, which have long vines. Still, the plants require a lot of real estate. Provide 30 inches of room between each. The good news is squash is very productive, so you don’t need many plants.
Because the plants are so productive, they are heavy feeders that require a steady supply of nutrients. I find that if I take the time before planting to thoroughly prepare the soil by amending it with a generous amount of compost, well-rotted manure and composted shredded leaves, not only do the amendments meet all the nutrient requirements, they also improve the soil to ensure it has the proper drainage that is key to growing squash successfully.
Summer squash prefer soil with a pH in the range of 6.0 to 6.5. You can get a soil test to find out the garden’s pH, and the test results will also reveal any nutrient deficiencies. Also be sure that the planting location receives full sun — that’s 6–8 hours of direct sunlight daily in the growing season.
After planting, apply 2–3 inches of organic mulch around the plants, such as shredded leaves or straw, to suppress weeds, retain moisture and prevent the leaves and fruit from contacting the soil.
If plants have lots of flowers but little to no fruit, there may be a pollination issue — as in bees and other pollinating insects are not reaching the flowers. You can overcome this by hand-pollinating.
Start by identifying a female flower. You can tell it’s female because there will be a small embryonic fruit between the flower and the stem. This embryonic fruit needs to be pollinated before it will grow and mature. Pick a male flower — it will have nothing between the flower and the stem — and peel back the petals to reveal the pollen-covered anther. Brush the anther around the stigma of the female flower, and then close the flower with a clothespin to allow the pollination process to complete. Another method is to take a small painter’s brush, dab it onto the anther to collect pollen, then lightly “paint” the pollen onto the stigma of a female flower.
Types and Varieties of Summer Squash
Zucchini, also known as courgette and baby marrow around the world, comes in green or yellow, and there are a number of varieties in each color.
Black Beauty is a popular variety of zucchini that grows in bushes that are 3–4 feet wide with dark green fruit that are cylindrical, smooth, dark green and straight. Cavili is a highly productive, parthenocarpic variety (that means it does not require pollinators) with lime green fruit. Golden Glory has spineless stems and yellow fruit. Sunstripe is a yellow zucchini with cream-colored stripes. Yellowfin is golden yellow with superior disease resistance. Cocozelle is an Italian heirloom that’s green with ribbing and light green stripes.
Pattypan squash, also known as scallop squash, are small and round with scalloped edges. They come in green, yellow or bicolor, plus white, striped and speckled varieties are available.
Lemon Sun is a bright yellow pattypan with tulip-shaped fruit. Benning’s Green Tint is light green with pronounced scalloping. Y-Star is shiny yellow with a green blossom end. G-Star is dark green and ribbed. Sunburst is deep yellow with a buttery flavor.
Straightneck squash are long and straight, and thinner at the “neck,” which is closest to the stem. Some varieties are smooth while others are textured, and all are yellow.
Chiffon is yellow with smooth white flesh. Superpick can be grown larger than the typical straightneck while retaining its flavor and staying tender. Goldfinch is bright yellow with a unique central stem. Zephyr is yellow with a green blossom end.
Crookneck squash are similar to straightneck squash but bent at the neck and more bulbous at the end. They are yellow and range in texture from smooth to bumpy.
Yellow Crookneck is buttery and firm with warted fruit. Delta is very productive with buttery yellow fruit. Tempest is yellow and renowned for culinary use.
There are a number of ball-shaped summer squash, such as Eight Ball (dark green), Cue Ball (light green), One Ball (bright yellow) and Lucky 8 (light green and mottled).
Watering Summer Squash
Squash plants require an inch of water a week, or up to two inches during the hottest stretch of summer. If it has rained any less than an inch in a week, make up the difference with supplemental watering.
Avoid watering from overhead. Apply water at the base of plants, under the foliage, so the leaves remain dry. A layer of organic mulch will retain moisture in the soil while having the added benefits of stopping weed seeds from germinating and preventing soil-borne plant diseases from touching foliage.
Fertilizing Summer Squash
As mentioned above, squash is a heavy feeder. Start with well-amended soil, and if you like, side-dress established plants with compost periodically.
If you do choose to use a fertilizer, look for an organic fertilizer with an NPK ratio that has a lower first number than second number. The “N” stands for nitrogen, and that helps with foliar growth, while the “P” stands for phosphorus, which helps with fruit production — and fruit production is what you are looking for. I prefer organic fertilizers, which are slow-release, while synthetic fertilizers give a quick jolt of nutrients and pose the risk of nitrogen burn.
Summer Squash Pests & Diseases
Squash vine borer is a squash pest that destroys squash plants from the inside. The life cycle starts when an adult squash vine borer, a red and black day-time moth, lays eggs at the base of a plant on the stem or under the lower leaves. When larvae hatch from the eggs, they bore their way into the plant and eat the tissue inside the stems. The best way to control this pest is to prevent egg-laying. A physical barrier of floating row cover will keep the adult off the plants. Just be sure to remove the cover when the plant blooms so pollinators can reach the flowers. Aluminum foil wrapped around the first few inches of the stems is another effective barrier. You can inject liquid Bt, a biological control, into the vines as a preventative measure. For more information on managing this pest, read Squash Vine Borer Prevention & Control, my comprehensive guide.
Squash bugs are cucurbit pests that damage plant foliage as they feed and are a vector for cucurbit yellow vine disease. They use their mouthparts to suck sap right out of leaves, causing the leaves to wilt, dry up and die. The adults usually lay their bronze-brown and oval-shaped eggs on the underside of leaves between the veins. The nymphs hatch 10 days later and the bugs mature after another month or so. The adults are five-eighths of an inch long with flat, dark gray, almost black bodies, and six legs. Row cover, hand-picking and insecticidal soap are a few control methods. For more information on managing this pest, read Squash Bug Prevention & Control, my comprehensive guide.
Squash beetles are a pest found in the Eastern United States. They are orange-red with black dots and often confused for beneficial lady beetles. In fact, they are sometimes called squash lady beetles. Both the larvae and adults feed on squash leaves, and the adults will also feed on fruit. Floating row cover can stop the adults from landing on leaves to lay their yellow eggs. Hand-picking of eggs and adults will effectively control this pest.
Cucumber beetles are common cucurbits pests that sometimes target squash. They chew holes in leaves and pass a pathogen that causes bacterial wilt. Hand-pick beetles as you find them. If a cucumber beetle problem arose one year, chances are it will happen again the following year. Practice crop rotation so the cucumber beetle population does not build up in your garden.
Powdery mildew and downy mildew are fungal diseases that affect summer squash leaves. Plants severely affected by powdery mildew appear coated in white powder, and downy mildew causes yellow spots. To prevent mildew, plant in full sun and provide adequate spacing so air can circulate. Avoid overhead watering that creates a welcoming environment for fungal spores. Water underneath leaves, possibly with a drip irrigation system or soaker hoses. Read my comprehensive guide Powdery Mildew Prevention & Control for more information.
Zucchini yellow mosaic virus discolors foliage and stunts fruit growth. The virus is transmitted by aphids, so cover plants with floating row cover as soon as they are planted. Infected seed can also carry this virus, so only grow seed from trusted sources.
Harvesting Summer Squash
Once you see tiny fruit, check back often. Summer squash fruit are known to grow quickly, so once you spot a small one, check on it every day. With zucchini, pick once the fruit is 5–8 inches long. If you let it grow much longer, the fruit will lose its flavor and the rind will become tougher. With straightneck and crookneck squash, 4–5 inches is generally as long as they should be allowed to grow before they are picked. Pattypan should be 3–5 inches in diameter.
Never pull on a fruit. Use sharp pruners or garden shears to cut through the stem, leaving an inch or two of stem on the fruit. If the blossom hasn’t fallen off on its own already, remove it. Once picked, plan to cook immediately or within a couple of days. Summer squash can last up to 10 days if stored in a refrigerator with high humidity at 41° to 50°, and will suffer chilling injuries at cooler temperatures.
What are your secrets to grow summer squash successfully? Let us know in the comments below.
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Links & Resources
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joegardener Online Gardening Academy™: Three popular courses on gardening fundamentals; managing pests, diseases & weeds; and seed starting!
joegardener Online Gardening Academy Beginning Gardener Fundamentals: Essential principles to know to create a thriving garden.
joegardener Online Gardening Academy Growing Epic Tomatoes: Tomato expert Craig LeHoullier joins me in leading this course on how to grow healthier, productive tomato plants and how to overcome tomato-growing challenges.
joegardener Online Gardening Academy Perfect Soil Recipe Master Class: Learn how to create the perfect soil environment for thriving plants.
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