An ear of sweet corn with silks on the stalk
How to grow

Sweet corn

Frost-tender. Sow outdoors up to 2 weeks after your last frost. First harvest 60 to 95 days from sowing.

Photo: “Zea mays ‘Ilini Xtra Sweet’ ear on the plant” by Forest and Kim Starr, CC BY 3.0 US, via Wikimedia Commons (cropped).

  • Full sun6–8 hours or more
  • 7–10 in apartRows 24–36 in
  • 60–95 daysFrom sowing
  • Soil 50 °F +To sow
  • 1 in a weekEven watering
  • Frost-tenderKilled at 32 °F

Your dates

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

Look up the frost dates for this ZIP code
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From seed to harvest

  1. SowSeed goes inWeek 0
  2. SproutFirst shoots showWeek 1–2
  3. Leaf growthLeaves fill outWeek 2–3
  4. TasselTassels openWeek 6–9
  5. SilkSilks show on the earsWeek 7–10
  6. HarvestReady to pickWeek 9–14

How to plant and grow

  1. Wait for warm soil

    Sow after your last frost date once soil is at least 50 to 60 °F. Supersweet types need about 65 °F or the seed may rot.

  2. Plant in blocks

    Sow seed 1 inch deep, 7 to 10 inches apart, in blocks of at least 3 or 4 short rows. Corn is wind pollinated and fills ears poorly in one long row.

  3. Sow again

    For a steady supply, sow the same variety every 10 to 14 days into early summer, or plant early, mid and late varieties at once.

  4. Keep it watered

    Give at least 1 inch of water a week. Tasseling, silking and ear fill are the stages when dry soil costs you the most.

  5. Check the silks

    Ears are ready about 3 weeks after silks appear. Silks turn brown and dry, and a pierced kernel gives milky juice.

  6. Pick and chill

    Each planting gives a pick window of about a week. Harvest in the cool morning and refrigerate right away, since sweetness fades fast.

Common problems

A corn earworm caterpillar feeding at the tip of an ear of corn
Photo: USDA Agricultural Research Service, Public domain, via Wikimedia Commons.

Corn earwormPest

What you'll see: Caterpillars feed in the tip of the ear under the husk, leaving moist droppings. On okra they bore into the pods.

Prevent

  • Check ears from when the silks appear.
  • Cut away the damaged tip; the rest of the ear is fine to eat.

Organic options

  • Mineral oil on the silks just inside each ear, a few days after the silks appear. For organic growing, use an OMRI Listed narrow-range oil.
  • Spinosad on the silks as eggs hatch. Look for OMRI Listed products.

Conventional options

  • Same as organic: spinosad and oil on the silks are the home-garden picks.

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

A European corn borer moth resting with its wings spread
Photo: “Ostrinia nubilalis” by Donald Hobern from Copenhagen, Denmark, CC BY 2.0, via Wikimedia Commons (cropped).

European corn borerPest

What you'll see: Small holes in corn stalks and ears with sawdust-like droppings, and broken tassels. In peppers, larvae bore in under the cap and the fruit rots.

Prevent

  • Remove or till under corn stalks after harvest; larvae spend the winter in them.
  • Keep the garden and its edges weeded.
  • Check corn whorls for small holes and brown droppings when tassels appear.

Organic options

  • Bt (Bacillus thuringiensis kurstaki) or spinosad into the whorls when damage shows. Look for OMRI Listed products.
  • Cut away damaged parts of ears; the rest is fine to eat.

Conventional options

  • Carbaryl into the whorls, if sweet corn is on the label. A home garden seldom needs it.

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.

A striped flea beetle on the edge of a leaf
Photo: “Phyllotreta striolata P1210443a” by xpda, CC BY-SA 4.0, via Wikimedia Commons (cropped). The cropped version is shared under the same licence.

Flea beetlesPest

What you'll see: Many tiny round holes and pits in leaves, as if hit by buckshot. Tiny dark beetles jump when disturbed.

Prevent

  • Cover seedlings with row cover and seal the edges.
  • Plant a little later, so warm weather carries plants through the damage.
  • Sow radish ahead of the main crop as a trap crop.
  • Clear weeds and old crop debris.

Organic options

  • Spinosad, or OMRI Listed pyrethrins (without piperonyl butoxide).

Conventional options

  • Carbaryl, malathion or permethrin, if the crop is on the label. Older plants seldom need treatment.

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

A greasy grey-brown black cutworm caterpillar
Photo: USGS Bee Inventory and Monitoring Lab, Public domain, via Wikimedia Commons.

CutwormsPestSprays are rarely needed

What you'll see: Young plants are cut off at or just above the soil overnight. Fat gray or brown caterpillars curl into a C shape in the soil nearby.

Prevent

  • Put a cardboard or foil collar around each transplant, pushed a few inches into the soil.
  • Till the bed before planting, and pull weeds.
  • Keep a strip of bare, dry soil along the garden edge.

Organic options

  • Dig gently around cut plants and destroy the caterpillars.

Conventional options

  • Usually not needed in a home garden. Collars work better than sprays.
A shiny, segmented wireworm larva on soil
Photo: “Wireworm - Flickr - treegrow (1)” by Katja Schulz from Washington, D. C., USA, CC BY 2.0, via Wikimedia Commons (cropped).

WirewormsPestSprays are rarely needed

What you'll see: Thin, shiny, yellow-brown larvae bore narrow holes into potatoes, roots and seeds. Seedlings may wilt.

Prevent

  • Expect them in beds newly made from lawn or sod.
  • Bury chunks of potato as bait, dig them up after about a week, and destroy the larvae.
  • Rotate crops.

Organic options

  • Bait with potato or carrot pieces, and check and destroy the catch often.

Conventional options

  • Insecticides worked into the soil before planting are an option only where wireworms have been a serious problem; most are farm products.

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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