Annual
Zinnia (common garden zinnia)
Zinnia elegans · Asteraceae
Also called: Common zinnia, Youth-and-old-age, Elegant zinnia
Zinnia (common garden zinnia) (Zinnia elegans) is a moderate-water annual well suited to Tucson and the low desert. It thrives in full sun.
Zinnia (common garden zinnia) at a glance
- Water use
- Moderate (established)
- Sun
- Full sun (6+ hours). In peak summer some light afternoon shade reduces heat stress, but full sun gives the best bloom.
- Mature size
- 1-4 ft tall depending on variety; 6-18 in wide
- Growth rate
- Fast (blooms ~6-8 weeks from seed)
- Bloom
- Nearly every color except true blue - red, orange, yellow, pink, white, purple, green, and bicolors, Late spring through fall (May into October); a reliable monsoon-season bloomer if mildew is managed.
- Cold hardiness
- Frost-tender; killed by frost. Heat-loving but susceptible to powdery mildew when humidity rises during monsoon.
- Soil
- Fertile, well-drained soil amended with compost; tolerates alkaline desert soil.
- Native range
- Mexico; grown as a warm-season annual in Tucson
- Best used as
- Cut flowers, Color beds and borders, Pollinator gardens, Containers
- Wildlife
- Excellent nectar source - strongly attracts butterflies and bees; seed heads feed finches and other birds.
- Toxicity
- Non-toxic to dogs, cats, horses, and humans (ASPCA) - pet- and child-safe.
How to grow Zinnia (common garden zinnia) in Tucson & the low desert
Watering
Direct-sow or transplant after frost danger passes, mid-March through May (a second sowing can go in with monsoon rains in July). Water deeply and consistently 2-3 times weekly; water at the base early in the day and keep foliage dry to prevent powdery mildew, which is the main summer problem here.
Fertilizer & nutrients
Moderate feeder. Amend beds with compost; apply a balanced fertilizer at planting and feed every 3-4 weeks with a bloom-type fertilizer (higher P-K) during the growing season for continuous flowering.
Pruning & care
Deadhead spent blooms regularly to prolong flowering, and pinch young plants at 4-6 in to promote bushy, branching growth and more cut flowers.
Notes
Prone to powdery mildew in Tucson's monsoon humidity; choose resistant series (e.g., 'Profusion', 'Zahara' interspecific hybrids) or provide air circulation and avoid overhead watering. Tougher than it looks in heat if mildew is controlled.
Sources: University of Arizona Cooperative Extension - Pima County Monthly Gardening Guides (March-May); ASPCA Toxic and Non-Toxic Plants; Arizona Master Gardener / Growing in the Garden Arizona Annual Flowers Guide