Vegetable
Watermelon
Citrullus lanatus · Cucurbitaceae
Also called: Watermelon
Watermelon (Citrullus lanatus) is a moderate-water vegetable well suited to Tucson and the low desert. It thrives in full sun, with a fast growth rate. Expect yellow blooms Yellow flowers ~5-8 weeks after sowing.
Watermelon at a glance
- Water use
- Moderate (established)
- Sun
- Full sun (8+ hours); thrives in Tucson's intense heat and long growing season. Maximum sun yields sweetest fruit.
- Mature size
- Vines 8-15+ ft; fruit ranges from 5-10 lb (icebox types) to 20-40+ lb (large varieties).
- Growth rate
- Fast
- Bloom
- Yellow, Yellow flowers ~5-8 weeks after sowing; harvest ~75-95 days (longer for large varieties). Spring-sown crop ripens mid-to-late summer (July-September).
- Cold hardiness
- Frost sensitive warm-season annual needing a long, hot season; ideal for USDA 9a-9b. Killed by frost.
- Soil
- Well-drained sandy loam with compost; tolerates alkaline desert soils, prefers pH 6.0-7.5. Plant on raised hills/mounds for drainage and warmth.
- Native range
- Northeastern Africa (Sudan/Sahel region). Not native to the Sonoran Desert, but related desert-adapted landraces (e.g., Tohono O'odham/Hopi heirloom melons) are traditionally grown in the Southwest.
- Best used as
- Fresh eating, Home vegetable garden, Heirloom/desert-adapted melon cultivation
- Wildlife
- Flowers attract bees and native pollinators essential for fruit set; ripe fruit attracts javelina, rodents, and birds (protect fruit).
- Toxicity
- Non-toxic; flesh safe for people and, in small seedless amounts, for dogs (avoid rind/seeds for pets). Safe edible crop.
How to grow Watermelon in Tucson & the low desert
Watering
Water deeply and consistently during vine growth and fruit development (2-3x/week, more in June-July heat); ease off watering as fruit approaches ripeness to boost sugar and prevent splitting. Deep, infrequent irrigation encourages deep roots; avoid overhead watering.
Fertilizer & nutrients
Mix compost and balanced fertilizer into hills at planting; side-dress nitrogen (ammonium sulfate) early as vines run, then reduce nitrogen and favor phosphorus/potassium at flowering/fruiting for sweetness. Too much nitrogen gives vines, not melons.
Pruning & care
Not typically pruned; vines sprawl widely. Optionally pinch off late-forming fruit so the plant ripens earlier-set melons before season's end. Set ripening fruit on mulch/cardboard.
Notes
Strong Tucson choice thanks to the long, hot season. Direct sow on mounds after frost danger and soil warming, mid-March through May. Needs lots of space; give vines room or guide them. Determine ripeness by a yellow ground spot, dried/brown tendril nearest the fruit, and dull hollow thump. Watch for powdery mildew, anthracnose, and squash bugs/cucumber beetles. Native/heirloom desert varieties are notably drought- and heat-tolerant.
Sources: University of Arizona Cooperative Extension (Pima County) vegetable planting calendar; Pima County Master Gardeners; Native Seeds/SEARCH desert-adapted melon guidance; Arizona low-desert melon culture