Annual
Petunia
Petunia x hybrida · Solanaceae (nightshade family)
Also called: Garden Petunia, Grandiflora/Multiflora Petunia
Petunia (Petunia x hybrida) is a moderate-water annual well suited to Tucson and the low desert. It thrives in full sun in cool months, with a fast growth rate.
Petunia at a glance
- Water use
- Moderate (established)
- Sun
- Full sun in cool months; provide morning sun with afternoon shade as spring heats up. At least 5-6 hours of sun for good bloom.
- Mature size
- Mounding types 6-12 in tall; spreading types trail 18-36 in. Width 12-36 in depending on type.
- Growth rate
- Fast
- Bloom
- Wide range - white, pink, red, purple, blue, yellow, bicolors and patterns., Fall through spring in the low desert; peak bloom in mild weather, fading by late spring/early summer heat.
- Cold hardiness
- Frost-sensitive (damaged below ~32F but tolerates light frost better than many annuals); heat-limited above ~90F. Grown as a cool-season annual in 9a-9b.
- Soil
- Light, fertile, well-drained soil enriched with compost; slightly acidic to neutral pH preferred.
- Native range
- Hybrid of South American species (Petunia axillaris x P. integrifolia); not native to Arizona.
- Best used as
- Cool-season color beds, Borders and mass plantings, Hanging baskets and containers, Window boxes
- Wildlife
- Flowers attract bees, butterflies, and hummingbirds; can be nibbled by rabbits.
- Toxicity
- Non-toxic to dogs, cats, and children (ASPCA lists petunia as non-toxic).
How to grow Petunia in Tucson & the low desert
Watering
Classic COOL-SEASON annual in Tucson: plant transplants from October through February (or start in pots in late January) for fall, winter, and spring color; it declines and goes leggy once daytime temps regularly exceed ~90F. Water to keep soil evenly moist - beds 2-3x/week, hanging baskets often daily in warm weather. Avoid wetting foliage to limit disease.
Fertilizer & nutrients
Heavy bloomer that needs regular feeding: apply a bloom-boosting (higher-phosphorus/potassium) water-soluble fertilizer every 1-2 weeks; spreading/Wave types are especially hungry.
Pruning & care
Pinch young plants and deadhead/shear leggy stems by about one-third mid-season to renew flowering and keep plants full.
Notes
In Tucson, treat petunias as a fall-to-spring crop, not a summer plant. Starting them in containers in late January gives a strong spring show before the heat arrives. Replant fresh each cool season.
Sources: University of Arizona Cooperative Extension - Pima County Monthly Gardening Guides; Pima County Master Gardeners; ASPCA non-toxic plant list