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How to Grow Zucchini and Summer Squash

How to Grow Zucchini and Summer Squash

Summer squash growingZucchini and summer squashes are frost-tender, warm-season annuals. The most popular summer squashes are crookneck, straightneck, scallop, and zucchini.
Start to grow zucchini and summer squash usually no sooner than 3 weeks after the last frost in spring.

Summer squashes grow best in air temperatures ranging from 60° to 75°F (15°-23°C); established fruit will ripen in temperatures as high as 100°F (37°C) but flowers will drop in high temperatures.

Pattypan summer squash
Scallop summer squash

Squashes which include zucchini are a large group within the cucumber family, Cucurbita, and include gourds, pumpkins, and summer and winter squashes. Summer squashes are eaten when they are immature, usually when their skins are soft and thin; winter squashes are eaten mature after their skins have thickened and hardened. Summer squash commonly grows as a bush or smaller weak-stemmed vining plant. Squashes have large, broad leaves; 4 to 6 stems or short vines grow from a central root. Fruits vary in shape from round to cylindrical to scalloped much as their names imply: crookneck, straightneck, scallop, and zucchini. Separate male and female flowers appear on the same plant.

Squash Yield. Grow 1 or 2 summer squash plants per household member.

Where to Plant Squash

Plant squash in full sun. Grow squash in loose, well-drained soil rich in organic matter. Prepare planting beds in advance working in plenty of aged compost. Add aged manure to planting beds the autumn before growing squash. Squash prefers a soil pH of 5.5 to 6.8. Summer squashes will sprawl slightly; if space is tight train them over small A-frame trellises.

Squash seedling
Sow squash seeds in the garden–or set out seedlings started indoors–only after the soil has warmed to at least 60°F

Zucchini and Summer Squash Planting Time

Summer squashes are frost-tender, warm-season annuals. Sow squash seeds in the garden–or set out seedlings started indoors–only after the soil has warmed to at least 60°F (16°C), usually no sooner than 3 weeks after the last frost in spring. Start squashes indoors as early as 4 weeks before the last average frost date in spring. Sow seed indoors in biodegradable peat or paper pots that can be set directly in the garden so as not to disturb plant roots. Summer squashes grow best in air temperatures ranging from 60° to 75°F (16-24°C); established fruit will ripen in temperatures as high as 100°F (37°C) but flowers will drop in high temperatures. Squashes are warm-season crops and very sensitive to cold and frost. Summer squashes require 50 to 65 days to reach harvest.

Planting and Spacing Zucchini and Summer Squash

Sow squash seeds 2 to 3 inches deep. Sow squash in raised hills or inverted hills 4 to 5 seeds set 3 to 4 inches (7-10cm) apart; thin to the two strongest seedlings. Space hills 6 to 8 feet (1.8-2.4m) apart. In rows, plant 2 squash seed 10 inches (25cm) apart in rows 3 to 5 feet (.9-1.5m) apart; thin successful seedlings in rows to 3 feet (.9m) apart. Thin seedlings by cutting off weak seedlings at soil level with scissors so as not to disturb fragile roots. Hills or mounds should be 6 to 12 inches (15-30cm) tall and 20 inches (50cm) across. This will allow plants to run down the hill away. Inverted hills–which can be used to retain moisture in dry regions–can be made by removing an inch of soil from an area about 20 inches across and using the soil to form a ring or circle. Plant 4 or 5 seeds in each inverted hill. Summer squashes can be trained up a fence or trellis. Set supports in place at the time of planting so as not to disturb growing roots.

More tips: Summer Squash and Zucchini Seed Starting Tips.

Straightnext summer squash
Straightneck summer squash

Water and Feeding Zucchini and Summer Squash

Squash grows best in soil that is kept evenly moist. Squashes require a lot of water in hot weather. Plants may wilt on hot days as they use water faster than the roots can supply. As long as the water is regular and deeply applied, wilted plants will liven up as the day gets cooler. Squash that is wilted in the morning needs immediate water. Add aged compost to planting beds before planting and side-dress squash with aged compost at midseason. Side dress squash with compost tea every 2 to 3 weeks during the growing season. Avoid feeding squash with high nitrogen fertilizer, 5-10-10 is best.

Companion plants. Nasturtiums, bush peas, beans. Avoid planting summer squashes in the shadows of taller plants.

Squash blossomsZucchini and Summer Squash Care

Squashes have separate male and female flowers. The first flowers to appear are male flowers that will not produce fruit. Female flowers appear slightly later and are pollinated by the male flowers commonly with the help of insects. If pollination is slow or does not occur, use a soft-bristled brush to dust inside a male flower then carefully dust the inside of a female flower (a female flower will have an immature fruit on its stem, a male won’t).

Once fruits form set each one on a wooden plank so that it does not have direct contact with the soil; this will allow squashes to mature with less exposure to insects.

More tips: Squash Growing.

Container Growing Zucchini and Summer Squash

Bush-type summer squash can be grown in containers. Sow 2 or 3 seeds in the center of a 10-inch (25cm) container; thin to the strongest seedlings once plants are 3 to 4 inches (7-10cm) tall. Extend the growing season by planting early and moving pots indoors when frost threatens. Set a cage or trellis in place at planting to save space.

Squash Pests and Diseases

Pests. Squash can be attacked by squash bugs, squash borers, and cucumber beetles. Handpick or hose away beetles. A small hole in the stem or unexplained wilting may indicate the presence of borers. Slit the stem, remove the borers, and dispose of them. Cover the slit stem with soil to encourage root development from that point.

Squash borers or bacterial wilt can cause squash plants to suddenly wilt and die just as they begin to produce. Bacterial wilt can be spread to squash by cucumber beetles; handpick and destroy cucumber beetles.

Diseases. Squashes are susceptible to bacterial wilt, mosaic virus, and mildew. Plant disease-resistant varieties. Keep the garden clean and free of debris where diseases and pests may harbor. Water at the base of plants to keep water off the foliage, and do not handle plants when they are wet to avoid the spread of fungal spores. Remove and destroy infected plants before they spread the disease to healthy plants.

More on diseases and pests: Zucchini and Squash Growing Problems: Troubleshooting.

  • Powdery mildew, a fungus disease, will cause leaves to turn a gray-white color late in the season. Proper spacing and increased air circulation will help reduce this problem.
  • Mosaic virus can cause squash plants to become mottled yellow and stunted. Mosaic virus is spread by aphids. Control aphids and remove affected plants.
  • Blossom end rot will cause squash fruit to rot from the blossom end. Blossom end rot is caused by fluctuations in soil moisture. Water evenly and regularly and mulch around plants to conserve soil moisture.

Summer squash harvestZucchini and Summer Squash Harvest

Summer squashes are ready for harvest 50 to 65 days from sowing. Pick summer squashes young when rinds are still tender and before seeds have formed. Harvest zucchini and crookneck varieties when they are 5 to 10 inches (12-25cm) long (4 to 7 inches/10-17cm long for yellow varieties); harvest scallop and round types when they are 3 to 5 inches (7-12cm) in diameter. Break the squashes from the stem, or use a clean knife to cut the fruit away. Do not let summer squash mature; that will suppress flowering and reduce the yield.

Squash blossoms
Squash blossoms are edible.

Squash flowers are edible. Pick and eat male flowers so as not to reduce the productivity of the plants. Squash flowers are often dipped in a batter and deep-fried.

Storing and Preserving Zucchini and Summer Squash. Summer squashes will keep in the refrigerator for up to one week. Do not wash squashes until you are ready to use them. Cooked squash can be frozen, canned, pickled or dried.

More harvest and kitchen tips: Summer Squash: Kitchen Basics.

 Varieties of Zucchini and Summer Squash

Crookneck: Aztec (55 days); Bandit; Crescent (53 days); Early Summer Yellow (53 days); Golden Dawn; Horn of Plenty; Medallion; Milano (42 days); Sundance (52 days); Supersett (50 days).

Straightneck: Butterstick (50 days); Early Prolific (50 days); Enterprise; Gold Slice; Goldbar (50 days); Multipik; Precious; Seneca Prolific (51 days); Sunbar (43-54 days).

Scallop or pattypan: Benning’s Green Tint (54-63 days); Butter Scallop (50 days); Golden Bush (68 days); Patty Pan (50 days); Peter Pan (60 days); Scallopini (60 days); Sunburst (50 days); Yellow Custard (50 days).

Costata Romanesca

Zucchini: Ambassador (55 days); Aristocrat (48 days); Arlesa (45 days); Black Beauty (58 days); Black Jack (55 days); Chefini (51 days); Clarimore Lebanese (44 days); Cocozelle (striped-45 days); Condor (48 days); Costata Romanesca (80 days); Dark Green (44-60 days); Elite; Embassy (49 days); Gold Rush (50 days); Golden Dawn (45 days); Goldfinger (41 days); Greyzini (55 days); Jackpot; Lebanese Light Green (40 to 50 days); Magda (45 days); Midnight; Milano (42 days); Onyx; Raven (42 days); Ronde de Nice (45 days); Round Green (52 days); Seasons; Seneca (47 days); Spacemiser; Spineless Beauty; Tatume (52 days) ; Tipo (55 days); Viceroy.

More on squash you can grow: Summer Squash Varieties: Best Bets and Easy-to-Grow.

Common name. Summer squash, crookneck, pattypan, straightneck, scallop, zucchini.

Botanical name. Cucurbita species.

Origin. American tropics

More tips: Squash and Pumpkin Growing Tips.

Grow 80 vegetables: THE KITCHEN GARDEN GROWERS’ GUIDE

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25 Comments

  1. Thank you for so much information. Best website so far that I have visited.
    I will be back many times to visit for information,.
    I live in the High Desert in California on your way to Vegas.
    It is very dry and hot.
    First year planting in containers.
    The wind is very is strong and gusts are worse. I have lost many seedlings
    from the wind I will search for a cover to protect. Do you have a idea on what I should buy?
    Thank You, Shirley

  2. I want to plant acorn and butternut squash, but I have only one garden and don’t want them to cross pollinate. Can I stagger the planting to avoid that? How long between plantings to keep them from blossoming at the same time?

    • Look at the days to maturity for the two plants you are growing. Plant the variety with the longest days to maturity first. At about one-third, the days to maturity of the first variety then plant the second variety. The bloom times will be staggered. Once the first variety has set fruit–two or three squash, nip off further blooms to prevent cross-fertilization when the second blooms.

  3. I live in South Texas and the temps are in the high 90’s closer to 100. My yellow and zucchini squash plants have done very well and yielded quite a lot of squash. I noticed as the temperatures got closer to 100 the plants started producing fewer blooms. How long can I expect the plants to produce and when should I pull the plants and begin preparing for the fall garden?

    • Zucchini and most vegetables will slip into a period of dormancy when temperatures are hotter than 95F; the plant simply can’t function as it would in more moderate temperatures. When the temperatures moderate and fall back into the 80sF, the plant will regain its vigor and continue to grow. In the meantime the plant will be dormant or suffer; if temps grow to hot, the plants could die. You can keep the plants watered; this will help. If the planting bed is not too large you can place stakes at the corners of the bed and drape shade cloth over the top to protect the plants from the midday sun. And, of course, you can pull the plants, amend the beds with aged compost and prepare for late summer or fall planting.

    • Hi, It get’s over 100 here in Northern California also in the Central Valley and I have put up an Gazebo over my garden because the sun is so intense and it has burned out my strawberries so I said no more and came up with that idea.

  4. Hello
    This is my first time growing zucchini and I m so stumped. I’m growing in cloth containers one plant has like a black mold on base of stem. All three plants have black spots on leaves and yellowing. I’ve added eggshells, sprayed with neem oil, baking soda mixture. I cut off most leaves, I don’t see any aphids. Should I just throw them out. They are still producing zucchini. I’m in Sacramento so it’s hot and they will everyday in this hot weather.

    • Black mold or a black bacterial infection can be caused by overwatering or by a soil-borne disease. If a bacterial disease is present in the stem you will soon see black spreading up the stem and likely infecting the leaves; the plant you be removed and placed in the trash and the soil should be replaced. If it is a mold associated with overwatering, you may be able to get rid of it by allowing the surface the soil to dry out between waterings–and sprinkling sand on the soil surface.

  5. My space is limited. Is it a good idea to cut off leaves/thin out with pruners on Yellow Crockneck Squash to allow more light and ventilation? If so, then which leaves and how much removal is okay?

    • For continued blooming and fruit set do not remove leaves. If you want to limit the growth of the plant, you can start at the end of a stem and work backwards; this will likely reduce yield. If you want to remove leaves nearer to the crown of the plant, remove every third or fourth leaf.

  6. I had believed I was growing summer squashed due to.my plant producing yellow vegetables. But as of the last week my plant produced a rather thick and long green vegetable. Is this typical for this kind of plant and if so what caused it and what kind of plant do I have?

    • You may have a crook-neck or straight-neck summer squash–these squashes have long necks. Check your seed packet; sometimes seeds not on the label can stray into other packets.

  7. Can you explain cross pollination. My understanding is that the seeds planted grow true to type. Then fruit Understand is true but if the seeds are kept and down the next year can have the cross pollination in them. Isbthisbso?

    • Cross-pollination often implies cross-fertilization. Cross-pollination is the transfer of pollen from one flower to another flower on a different plant.

  8. I have grown zucchini for almost 40 years and always enjoyed it, but I didn’t realize how good it could be until growing Costata Romanesco. I had a house guest/inexperienced laborer a decade ago through a farm program who brought with her various seeds her mother had bought but hadn’t grown, and a package of this heirloom Italian variety was among them. I planted it straight into the dirt, the way I always do. (I have a theory about squash being more robust if planted that way.) They were very near the cucumber plants that I planted the same way, and when this striped fruit showed up, I really had no idea what I had done. Had I inadvertently planted English cucumbers or what? I decided to taste it in the garden, and I ended up eating the entire squash where I stood. Try doing that with one of the varieties more familiar to Americans. You’ll end up with a shirt soaked with squash juice. I have never grown any kind of summer squash since–it’s that delicious.

    As to my theory about planting directly: On some things that can be planted either way, cucumbers and squash among them (and, oddly, basil), I have found through trial and error that they are sturdier and healthier if the seeds are just planted in place. All germinate readily anyway in warm weather, and I have my hands full (and the real estate under my indoor garden lights and atop the heat mat full enough) without messing with anything that works just by burying it in the ground.

    But the main point is that the Costata Romanesco was a real revelation to me, a bit like discovering what squash must taste like in heaven..I urge everyone to try it.

  9. I am planting zucchini for the first time. The leaves of one plant are turning yellow. I am watering quite a lot so the soil is not dry. So I’m wondering why. I’m a novice!

    • There are several reasons leaves turn yellow; one is overwatering. Allow the soil to nearly dry between waterings. If you are unsure you can use a moisture meter to tell you how wet the soil is. Once a plant is established–about 6 inches tall or taller– we allow the top inch of soil to nearly dry out before we water again.

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