Annual
Geranium
Pelargonium x hortorum · Geraniaceae
Also called: Zonal Geranium, Garden Geranium, Bedding Geranium
Geranium (Pelargonium x hortorum) is a moderate-water annual well suited to Tucson and the low desert. It grows to 12-24 in tall and 12-18 in wide, with a moderate growth rate.
Geranium at a glance
- Water use
- Moderate (established)
- Sun
- Full sun in the cool season; in spring shift to morning sun with afternoon shade. Full afternoon sun scorches foliage once temperatures climb above the mid-90s.
- Mature size
- 12-24 in tall and 12-18 in wide
- Growth rate
- Moderate
- Bloom
- Red, pink, salmon, white, lavender, and bicolors, Late fall through spring in Tucson (peak Feb-May); declines as summer heat arrives.
- Cold hardiness
- Frost-tender; damaged below about 32 F. Protect or treat as a winter annual that is replaced before intense summer heat.
- Soil
- Well-drained, loose soil amended with compost; tolerates Tucson's alkaline soils but resents standing water. Excellent in containers with a quality potting mix.
- Native range
- Garden hybrid; parent species native to South Africa. Grown as a cool-season annual in Tucson.
- Best used as
- Containers and pots, Cool-season color beds, Window boxes and patio displays, Borders and entryway accents
- Wildlife
- Minor pollinator value; not a significant Sonoran Desert wildlife plant. Often considered somewhat deer- and rabbit-resistant due to scented foliage.
- Toxicity
- Toxic to dogs, cats, and horses (Pelargonium oils, including geraniol/linalool, cause vomiting, depression, and dermatitis). Generally only mildly irritating to humans.
How to grow Geranium in Tucson & the low desert
Watering
Plant in fall (Oct-Nov) or late winter for a cool-season display; treat as a frost-tender annual that fades in summer heat. Keep soil evenly moist but not soggy, watering when the top inch dries; container plants dry fast and may need watering every 1-2 days in spring.
Fertilizer & nutrients
Feed every 2-4 weeks during active growth with a balanced or bloom-type (higher-phosphorus) water-soluble fertilizer; light, frequent feeding gives the best flowering in our fast-draining soils.
Pruning & care
Deadhead spent flower clusters by snapping the stalk at the base to keep blooms coming; pinch leggy stems to encourage bushiness.
Notes
In Tucson, true Pelargonium 'geraniums' are grown as a cool-season annual or short-lived container plant, not a summer bedding plant as in cooler climates. They bloom beautifully fall through spring, then decline in the intense low-desert summer; give afternoon shade as temperatures rise and overwinter in a protected spot or against a warm south wall during frosts. Do not confuse with true hardy Geranium (cranesbill).
Sources: University of Arizona Cooperative Extension / Pima County Master Gardeners; AMWUA (wateruseitwisely.com); ASPCA Toxic and Non-Toxic Plant List