Types and days to harvest
Garden radishes (Raphanus sativus var. radicula) are round or carrot-shaped; daikon (R. sativus var. longipinnatus) is a long, white Asian radish, usually milder, planted in late summer for late fall harvest (UMN).
| Type | Days from sowing | Notes |
|---|---|---|
| Spring | 25–30 (UW); young roots 20–30 (UF/IFAS) | Globe-shaped, red, white, pink or purple; 'Cherry Belle', 'Early Scarlet Globe' (UW) |
| Summer | About 50–60 (UW) | Larger and slower than spring types (UW). 'French Breakfast' handles heat better than most early types (Illinois) |
| Winter | About 50–60 (UW) | Favors cool temperatures and short days (UW). Sown mid to late summer; usually more pungent and longer-keeping (Illinois) |
| Daikon | About 7 weeks in spring, 10 in fall (UF/IFAS) | Can weigh 5–6 lb and keep good quality (Illinois). Use raised beds, and shorter varieties in stony or heavy soil (UMN) |
- 1. Days from sowing to harvest: UF/IFAS 20–30; UW–Madison spring types 25–30, summer and winter types 50–60; UMD 25–35; CSU 30; USU 25–45; UMN 3–5 weeks; WSU 3–6 weeks
- 2. Square-foot grid: 16 radishes per square foot, 3 in apart (UF/IFAS, NC State)
- 3. Trap-crop row: radishes interplanted every 6 or 12 in among cole crops (ATTRA)
Timing and germination
| Question | Figures given |
|---|---|
| Soil temperature to sow | At least 40°F (CSU, USU), measured at 4 in deep at 8 a.m. (CSU) |
| Germination | Optimum 80°F, maximum 90°F (CSU); best at 55–75°F (USU) |
| Days to emerge | 3–10 (CSU); 5–10 (USU); within about 10 (UMN) |
| Spring sowing | 2–4 weeks before the last frost (CSU, UNH); 2–3 weeks before (USU); as soon as the soil can be worked (UMD, Illinois); about April 15 in southern Wisconsin (UW); early April to early May in Minnesota (UMN) |
| Fall and winter sowing | August 1 to September 1 in Minnesota (UMN); mid to late August or early September in Utah (USU); in Florida, September through March is the best season (UF/IFAS) |
| Best growing temperature | Rapid growth at about 60–65°F gives the best flavor (UW); at or below 80°F (USU) |
- Loosen the soil at least 6 in deep, a foot or more for long types; pH 6–7 (UMN).
- Sow 1/4–1/2 in deep (UMD, Illinois), seed 1–2 in apart (UMD). Do not transplant; it disturbs the root (UF/IFAS).
- Keep the surface uniformly moist (USU); if it crusts, sprinkle lightly (UMN).
- Thin early; thinnings are good to eat (Illinois).
- Water evenly, at least 1 in per week (UMN). Slow growth makes radishes hot and woody (Illinois).
- Sow again every 5 days (UMD), 10 days (USU, WSU) or 10–14 days (Illinois, UW).
Find your dates on frost dates explained or count back with the planting calendar.
Spacing and interplanting
| Source | Final spacing |
|---|---|
| Illinois | Spring types 1/2–1 in; winter types 2–4 in or more; beds 2–3 in each way |
| UW | Spring 1 in, rows 1 ft; winter 2 in, rows 18 in |
| USU, WSU | 1–2 in; rows 10–12 in (USU) |
| UMN | About 2 in; daikon 4–6 in |
| UMD | 2–4 in, depending on type |
| CSU | 2–3 in each way in block beds on soil with 4–5% organic matter |
| UF/IFAS, NC State | 16 per square foot, 3 in apart |
Fast-sprouting radishes can mark rows of slow crops such as carrots, beets and lettuce and be pulled before the companion matures (UMD; see carrots), or fill gaps later used for peppers, tomatoes and squash (Illinois). Compare other crops on square foot gardening spacing.
Containers
- Size: 1–3 gallons, 4–6 in deep (UMD); at least 2 gallons, 4–6 in deep (UW–Madison); 2 quarts, 4–6 in deep, plants 2–3 in apart (NC State); at least 6 in deep with drainage holes (WSU). See container sizes for vegetables.
- Mix: loose, well-drained potting mix, plants 2–4 in apart, no rock layer at the bottom (UW–Madison).
- Water and light: never let the mix dry out completely; move pots somewhere cooler in hot summers (WSU). At least 6 hours of sun, ideally 8–10 (UMD).
Harvest and problems
Pull spring radishes at about 1 in across (UMD) or while still under 1 in (Illinois); they turn pithy quickly if left (UW). Winter types are harvested much larger, pulled before the ground freezes and kept in moist cold storage for several months (Illinois).
| Problem | Causes named |
|---|---|
| Hot or woody roots | Overmature roots or hot weather (UMD); slow growth or age, not size (Illinois) |
| Cracked or split roots | Old roots, or a flush of moisture after dry spells (Illinois); uneven moisture (UMN); heavy watering after drought (USU) |
| All tops, no roots | Overcrowding, heat, late planting or heavy shade (Illinois); excess nitrogen (UMD) |
| Bolting | Heat (UMN, USU); stress in the first 6 weeks (USU); warm weather once roots reach edible size (UW) |
Pests
| Pest | Signs | Non-chemical guidance |
|---|---|---|
| Flea beetles | Jumping beetles under 1/10 in; tiny pits and holes in leaves; rarely serious beyond the seedling stage (UC IPM). Worse in early spring (UMN) | Row cover until the sixth-leaf stage (UC IPM), sealed right after seeding, best after a non-susceptible crop so beetles do not emerge underneath (UVM, ATTRA). Remove debris in fall (UC IPM) |
| Cabbage maggot | Gray fly about 3/16 in; white larvae tunnel into roots, up to three generations a season; young plants suffer most (WSU). Root maggots are more common above 40° north latitude (Illinois) | Row covers before the flies emerge, never over soil infested last year; do not replant susceptible crops there (WSU). Avoid heavy manure, cover seedbeds, remove infested plants (UC IPM) |
This page gives no pesticide or fertilizer rates. Follow your soil test and any product label exactly, and ask your county extension office to identify problems.
Radishes as a trap crop
A trap crop is a planting the pest prefers, set out so insects gather on it instead of the main crop. The radish evidence is thin and farm-scale:
| Source | What it reports |
|---|---|
| WSU (Wolfe, 2020) | Intercropped radishes trap flea beetles, root maggots and cabbage maggots away from cabbage-family plants. Plant before the main crop flowers, re-sow every 2–3 weeks, and remove insects or infested parts often, or pests multiply there |
| ATTRA (2003, updated 2015) | Radishes interplanted every 6 or 12 in among cole crops; 'Chinese Daikon' and 'Snow Belle' named as preferred. One trial cited (Byczynski, 1999) found less damage to broccoli. ATTRA names Chinese Southern Giant mustard as the most practical flea beetle trap crop |
| UVM (Grubinger, 2003) | Radish, daikon and arugula are highly attractive to flea beetles. Trap crops should surround the planting, and trapped beetles must be dealt with quickly |
| WSU PNW640 (2012) | For flea beetle trap crops in general: plant before the main crop, at about 10% of the area; may not fully protect during heavy infestations |
Two cautions: a radish that works as a trap is full of beetles or maggots, since radish is itself a cabbage maggot host (WSU), and none of these sources measured a small bed. Radishes grown to eat belong under row cover. The companion planting chart rates other pairings.
Where sources disagree
| Question | Figures given |
|---|---|
| Days to harvest (spring types) | 20–30 (UF/IFAS) vs 25–30 (UW) vs 25–35 (UMD) vs 30 (CSU) vs 25–45 (USU) vs 3–5 weeks (UMN) vs 3–6 weeks (WSU) |
| Seed depth | No more than 1/4 in (UF/IFAS) vs 1/4–1/2 in (UMD, Illinois) vs 1/2 in (CSU, USU) vs 1/2–3/4 in (UW) vs at least 1/2 in (WSU) |
| Final spacing | 1/2–1 in (Illinois) vs 2–4 in (UMD) vs 3 in grid (UF/IFAS, NC State) |
| Container | 2 quarts (NC State) vs 2 gallons (UW–Madison) vs 1–3 gallons (UMD); 4–6 in deep vs at least 6 in (WSU) |
| Refrigerated storage | 5–7 days (Illinois) vs 1–2 weeks (UMD, UMN) vs 2–4 weeks (USU) |
Small-space checklist
- Sow spring types 2–4 weeks before the last frost; winter types and daikon in late summer.
- Loosen soil 6 in deep; pots at least 4–6 in deep.
- Sow about 1/2 in deep; thin spring types to 1–2 in (or 16 per square foot), winter types and daikon wider.
- Keep moisture even; re-sow every 5–14 days.
- Cover seedlings with sealed row cover against flea beetles and maggots.
- Pull at about 1 in across, before roots turn pithy or hot.
- Use radishes as a trap only if you will check and clear them often.
More crop pages: carrots, kale, spinach, lettuce, tomatoes and peppers.
Sources
- UF/IFAS Gardening Solutions — Radishes
- University of Maryland Extension — Growing Radishes in a Home Garden (updated 2026)
- University of Illinois Extension — Radish (Home Vegetable Gardening)
- University of Minnesota Extension — Growing radishes (Schuh and MacKenzie, reviewed 2024)
- Utah State University Extension — How to Grow Radishes in Your Garden (Dan Drost, 2020)
- University of Wisconsin–Madison Extension — Growing Carrots, Beets, Radishes, and Other Root Crops in Wisconsin: A Guide for Fresh-Market Growers (A3686, Delahaut and Newenhouse, PDF)
- Colorado State University Extension — Vegetable Planting Guide (CMG GardenNotes #720, reviewed 2024)
- University of New Hampshire Extension — Growing Vegetables: When to Plant Your Vegetable Garden (fact sheet)
- Washington State University SNAP-Ed — Growing in Washington: Radishes (adapted from WSU Extension EM0575E, PDF)
- Washington State University Extension, HortSense — Radish: Cabbage maggot
- University of Maryland Extension — Types of Containers for Growing Vegetables
- University of Wisconsin–Madison Extension — Growing Vegetables in Containers
- NC State Extension Gardener Handbook — Chapter 18, Plants Grown in Containers (Table 18-1)
- UF/IFAS Gardening Solutions — Square Foot Gardening
- NC State Plants for Human Health Institute — Square Foot Seeds (PDF)
- UC Statewide IPM Program — Flea Beetles (Home and Landscape)
- UC Statewide IPM Program — Cabbage Maggot (Home and Landscape)
- University of Vermont Extension — Flea Beetles (Vern Grubinger, 2003)
- NCAT / ATTRA — Flea Beetle: Organic Control Options (Kuepper 2003, updated by Dufour 2015, PDF)
- Washington State University Extension — Trap Cropping (PDF)
- Washington State University Extension — Organic Management of Flea Beetles (PNW640, Parker, Miles, Murray and Snyder, 2012)
All sources were opened and checked in October 2026. Rules and figures change; confirm with the original before acting.