Vegetable
Radish
Raphanus sativus · Brassicaceae
Radish (Raphanus sativus) is a moderate-water vegetable well suited to Tucson and the low desert. It thrives in full sun, with a fast growth rate.
Radish at a glance
- Water use
- Moderate (established)
- Sun
- Full sun (6+ hours); tolerates light afternoon shade in warmer parts of the cool season.
- Mature size
- Tops 6-10 in tall; roots vary from 1 in (round salad types) to 12+ in (daikon).
- Growth rate
- Fast
- Bloom
- White to pale pink/lavender (flowers only if bolted), Bolts and flowers in spring heat; grown for roots, not bloom. Harvest small types in ~22-30 days, daikon/winter types in 50-60+ days.
- Cold hardiness
- Cool-season; frost-tolerant and grows well through Tucson winters. Quality declines and plants bolt as temperatures climb in late spring.
- Soil
- Loose, well-drained sandy loam free of rocks and clods; amend Tucson's caliche/clay soils with compost and break up hardpan so roots can expand. Near-neutral pH.
- Native range
- Asia (southeast/central Asia); long domesticated, not native to the Sonoran Desert.
- Best used as
- Cool-season vegetable garden, raised beds and containers, fast succession/intercrop, fall and winter salads
- Wildlife
- Flowers (if allowed to bolt) attract bees and other pollinators.
- Toxicity
- Non-toxic to people and pets; edible root and leaves.
How to grow Radish in Tucson & the low desert
Watering
Keep soil consistently and evenly moist; in Tucson water roughly every 2-3 days in the cool season, more often in sandy soil. Even moisture is critical to avoid woody, cracked, or pithy roots.
Fertilizer & nutrients
Light feeder; mix a balanced fertilizer or compost into the bed before planting. Avoid excess nitrogen, which produces lush tops and small roots. A light side-dressing is rarely needed for the short crop.
Pruning & care
No pruning. Thin seedlings to about 1-2 inches apart once they emerge to give roots room to size up.
Notes
In Tucson plant seed in the cool season: late summer/fall (roughly Sept-Nov) and again in late winter/early spring (Jan-Mar). Avoid the hot months (radishes turn pithy, hot, and bolt). Direct-sow; they don't transplant well. Quick harvest makes them ideal for succession planting and for filling gaps between slower crops.
Sources: University of Arizona Cooperative Extension (Pima County) low-desert vegetable planting calendar; Pima County Master Gardeners; Arizona Master Gardener Manual