A summer squash plant with yellow fruits and flowers under its leaves
How to grow

Summer squash

Frost-tender. Sow outdoors up to 2 weeks after your last frost. First harvest 40 to 60 days from sowing.

Photo: “Straightneck summer squash plant and flowers” by megankhines from middleton, wisconsin, usa, CC BY-SA 2.0, via Wikimedia Commons (cropped). The cropped version is shared under the same licence.

  • Full sun6–8 hours or more
  • 24–48 in apartRows 3–6 ft
  • 40–60 daysFrom sowing
  • Soil 65 °F +pH 6.0–6.5
  • 1–2 in a weekEven watering
  • Frost-tenderKilled at 32 °F

Your dates

Put in your ZIP code to see when to start, plant and harvest summer squash where you live, from your own frost dates.

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From seed to harvest

  1. SowSeed goes inWeek 0
  2. SproutFirst shoots showWeek 1
  3. VinesRunners spread outWeek 3–4
  4. FlowersFlowers openWeek 5–6
  5. Fruit setsSmall fruit formsWeek 5–7
  6. HarvestReady to pickWeek 6–9

How to plant and grow

  1. Sow after frost

    Sow seeds 1/2 to 1 inch deep once frost is past and soil reaches 65 to 70 °F. Direct seeding usually does better than transplants.

  2. Thin to the best

    Plant a few seeds per spot and thin to one or two strong plants when they are 2 to 3 inches tall. Bush types need 2 to 4 feet each.

  3. Sow again later

    Plant part of the row first and the rest about 3 weeks later to spread the harvest and replace plants lost to pests.

  4. Water deeply

    Give 1 to 2 inches of water a week, soaking deeply rather than lightly. Wait to mulch until the soil is above 75 °F.

  5. Guard the stems

    Check for squash bugs, beetles and vine borer damage at the base. Remove row covers once flowers open so bees can pollinate.

  6. Pick young

    Harvest every day or two, a few days after the flower opens. Zucchini is best 6 to 8 inches long; pattypans at 3 to 4 inches across.

Common problems

A squash vine borer moth with an orange and black body
Photo: “Melittia cucurbitae P1440819a” by xpda, CC BY-SA 4.0, via Wikimedia Commons (cropped). The cropped version is shared under the same licence.

Squash vine borerPest

What you'll see: A vine wilts suddenly, and a hole near the base leaks orange, sawdust-like frass. A fat white larva is inside the stem.

Prevent

  • Cover vines with row cover when they start to run, and remove it at flowering.
  • Do not use row cover where squash grew last year; borers spend the winter in that soil.
  • Grow butternut squash, which is hit less often.
  • Pull and destroy vines killed by borers.

Organic options

  • Slit the stem lengthwise above the frass, remove the larva, and cover the cut with moist soil.
  • Bt sprays do not reach larvae inside the stem.

Conventional options

  • Carbaryl, permethrin, bifenthrin or esfenvalerate on the stem bases, starting when adults first appear.

Bee caution: Don't spray open flowers. Spray in the late evening, when bees aren't flying.

A cluster of squash bugs on a pumpkin
Photo: “Anasa tristis gathered on a pumpkin” by Ilona Loser, CC BY-SA 4.0, via Wikimedia Commons (cropped). The cropped version is shared under the same licence.

Squash bugPest

What you'll see: Flat gray-brown bugs and gray nymphs suck sap, leaving yellow spots that turn brown, and vines wilt. Bronze egg clusters sit under the leaves.

Prevent

  • Check leaf undersides each week from early summer and crush egg clusters.
  • Lay a board by the plants at night and destroy the bugs under it each morning.
  • Clear plant debris and mulch in fall.

Organic options

  • Hand-pick bugs and scrape off eggs.
  • OMRI Listed pyrethrins (without piperonyl butoxide) with diatomaceous earth around the base of the plants.

Conventional options

  • Esfenvalerate, permethrin or carbaryl, aimed at young nymphs soon after eggs hatch.

Bee caution: Don't spray open flowers. Spray in the late evening, when bees aren't flying.

A striped cucumber beetle, yellow with black stripes
Photo: “Acalymma vittatum P1310371a” by xpda, CC BY-SA 4.0, via Wikimedia Commons (cropped). The cropped version is shared under the same licence.

Cucumber beetlesPest

What you'll see: Yellow beetles with black stripes or spots chew seedlings, leaves and flowers. They spread bacterial wilt, which kills cucumbers and melons.

Prevent

  • Cover seedlings with row cover and seal the edges; remove it at flowering so bees can reach the blooms.
  • Clear weeds and plant debris where adults spend the winter.
  • Mulch with straw around established plants.

Organic options

  • Knock beetles into soapy water on small plantings.
  • Kaolin clay on the leaves deters feeding but does not kill beetles; apply it before damage builds.

Conventional options

  • Several garden insecticides are labeled for cucumber beetles; check the crop is listed. Spray early or late in the day to spare bees.
A squash leaf coated with white powdery mildew
Photo: “Powdery mildew 9” by Dmitry Brant, CC BY-SA 4.0, via Wikimedia Commons (cropped). The cropped version is shared under the same licence.

Powdery mildewDisease

What you'll see: White, powdery patches on the tops of leaves and on stems. Leaves yellow and dry, and fruit may ripen poorly.

Prevent

  • Grow resistant varieties.
  • Give plants sun and space for air flow.
  • Remove badly infected leaves, and clear debris after harvest.

Organic options

  • Sulfur or potassium bicarbonate, from the first spots. Sulfur can burn some vine crops in heat, and never use it near an oil spray.
  • Neem oil. Look for OMRI Listed products.

Conventional options

  • Myclobutanil or propiconazole, if the crop is on the label.

Bee caution: Don't spray open flowers. Spray in the late evening, when bees aren't flying.

A dense colony of grey aphids on a kale leaf
Photo: “Aphids on Kale leaf” by Sanjay Acharya, CC BY-SA 4.0, via Wikimedia Commons (cropped). The cropped version is shared under the same licence.

AphidsPest

What you'll see: Clusters of small, soft-bodied green, black or gray insects on new shoots and under leaves. Leaves curl, and a sticky film may coat them.

Prevent

  • Check leaf undersides each week; a few aphids do little harm.
  • Pull nearby weeds, such as wild mustards, that feed aphids.
  • Grow flowers for lady beetles, lacewings and hover flies, and avoid broad sprays that kill them.

Organic options

  • Knock aphids off with a strong spray of water.
  • Insecticidal soap or horticultural oil on leaf undersides, repeated as the label allows.
  • Neem oil, or OMRI Listed pyrethrins (without piperonyl butoxide).

Conventional options

  • Malathion or permethrin, if the crop is on the label. These also kill the insects that eat aphids.

Bee caution: Don't spray open flowers. Spray in the late evening, when bees aren't flying.

Read and follow the product label: it is the law. It sets the rate, the crops it is for, and the days between spraying and picking. Products registered vary by state; for organic growing, look for products allowed under the USDA National Organic Program (OMRI Listed). We name active ingredients, not brands or rates.

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Sources

Planting dates and growing facts checked against these university extension and USDA pages:

Growth-stage drawings: TallyTill.

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