A hand holding a bunch of freshly pulled red radishes
How to grow

Radishes

Takes a hard frost. Sow outdoors 2 to 4 weeks before your last frost; sow in fall 3 to 12 weeks before your first fall frost. First harvest 21 to 45 days from sowing.

Photo: “Freshly harvested radishes from a home garden” by Shixart1985, CC BY 2.0, via Wikimedia Commons (cropped).

  • Full sun6–8 hours or more
  • 1–2 in apartRows 10–12 in
  • 21–45 daysFrom sowing
  • Soil 40 °F +pH 5.5–6.5
  • ½–1 in a weekEven watering
  • HardyTakes a hard frost

Your dates

Put in your ZIP code to see when to start, plant and harvest radishes 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
  3. True leavesFirst real leavesWeek 1–2
  4. ThinThin to final spacingWeek 2
  5. Root swellsRoots thickenWeek 2–3
  6. HarvestReady to pickWeek 3–6

How to plant and grow

  1. Sow direct

    Sow seed 1/4 to 1/2 inch deep 2 to 4 weeks before last frost, once soil is about 40 °F. Radishes do not transplant well.

  2. Thin early

    Thin to 1 to 2 inches apart in rows about 12 inches apart. Crowded plants make leaves instead of roots.

  3. Water evenly

    Give about 1/2 to 1 inch a week. Dry or hot spells make roots woody and push plants to flower.

  4. Sow small, often

    Sow a short row every 7 to 10 days in spring for a steady supply. Stop when summer heat arrives.

  5. Sow for fall

    Start again in late summer, about 3 to 12 weeks before first fall frost. Cool fall weather gives crisp roots.

  6. Harvest young

    Pull roots 3 to 6 weeks after sowing, before round types pass about 1 inch across. Old roots turn pithy and hot.

Common problems

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 white cabbage maggot burrowing into a brassica stem at soil level
Photo: “Delia radicum, koolvlieg made” by Rasbak, CC BY-SA 3.0, via Wikimedia Commons (cropped). The cropped version is shared under the same licence.

Cabbage maggotPestNo spray helps

What you'll see: Small white maggots tunnel into radish and cabbage-family roots. Plants wilt, and roots are scarred or rotten.

Prevent

  • Cover seeded rows with row cover right after sowing, and bury the edges.
  • Do not cover ground that grew cabbage-family crops last year; flies can hatch under the cover.
  • Move cabbage-family crops to a new bed each year.

Organic options

  • Row cover is the main control. Pull and destroy infested plants.

Conventional options

  • None. No insecticide is labeled for cabbage maggot in home gardens.

BoltingGrowing problemNo spray helps

What you'll see: The plant sends up a flower stalk early, and the leaves turn small and bitter. Long days and heat set it off, and in bok choy and other cabbage-family greens so can a late frost or a week of nights below 50 °F.

Prevent

  • Sow in the cool, shorter days of spring and fall.
  • Sow small amounts every few weeks rather than all at once.
  • Choose varieties sold as slow to bolt.
  • Give afternoon shade in hot spells.

Organic options

  • Harvest as soon as a stalk starts. Let a few cilantro or dill plants flower for seed and for helpful insects.

Conventional options

  • None. No spray stops bolting.

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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