Annual
Trailing Petunia / Wave-type (Million Bells)
Calibrachoa x hybrida · Solanaceae (nightshade family)
Also called: Million Bells, Calibrachoa, Mini Petunia, Trailing Petunia
Trailing Petunia / Wave-type (Million Bells) (Calibrachoa x hybrida) is a moderate-water annual well suited to Tucson and the low desert. It grows to 6-12 in tall, trailing/spreading 12-24 in in full sun in cool months, with a fast growth rate.
Trailing Petunia / Wave-type (Million Bells) at a glance
- Water use
- Moderate (established)
- Sun
- Full sun in cool months; morning sun with afternoon shade as temperatures climb (especially in hanging baskets from April on).
- Mature size
- 6-12 in tall, trailing/spreading 12-24 in.
- Growth rate
- Fast
- Bloom
- Many - purple, magenta, pink, red, yellow, orange, white, and patterned/bicolor., Fall, winter, and spring in the low desert; slows in midsummer heat, can revive as it cools.
- Cold hardiness
- Frost-sensitive (below ~32F); heat-stressed in sustained 95F+. Grown as a cool-season/spring annual in 9a-9b.
- Soil
- Light, fast-draining, slightly acidic potting mix or amended bed; resents heavy, alkaline, waterlogged soil. Best in containers in Tucson.
- Native range
- Hybrid derived from South American Calibrachoa species; not native to Arizona.
- Best used as
- Hanging baskets and window boxes, Container 'spiller' plantings, Cool-season color beds and borders
- Wildlife
- Small tubular flowers attract bees, butterflies, and hummingbirds.
- Toxicity
- Considered non-toxic to dogs, cats, and children (not on ASPCA toxic lists; close relative of petunia).
How to grow Trailing Petunia / Wave-type (Million Bells) in Tucson & the low desert
Watering
Cool-season to spring annual in Tucson, planted from fall through early spring; tolerates heat somewhat better than standard petunias but takes a bloom break in peak summer. Keep evenly moist - it does not like to fully dry out; check hanging baskets DAILY in warm weather and water when the top of the mix feels dry. Prefers slightly acidic conditions and dislikes alkaline-water salt buildup, so flush containers periodically.
Fertilizer & nutrients
Vigorous feeder: apply a bloom-type water-soluble fertilizer every 1-2 weeks; iron chelate helps prevent interveinal yellowing (chlorosis) common with Tucson's alkaline water/soil.
Pruning & care
Self-cleaning (little deadheading needed), but shear back lightly if stems stretch or thin out to renew fullness.
Notes
Performs best in containers and baskets in Tucson where soil/water can be kept acidic and moisture controlled. Outperforms standard petunias in heat but still fades in deep summer - give it morning sun, afternoon shade, and watch for chlorosis from alkaline water.
Sources: Green Things (Tucson) plant database (greenthingsaz.com); University of Arizona Cooperative Extension low-desert annual guidance; Growing In The Garden - Arizona low-desert annuals