Annual
Pentas
Pentas lanceolata · Rubiaceae
Also called: Egyptian Star Flower, Egyptian Star Cluster, Star Flower
Pentas (Pentas lanceolata) is a moderate-water annual well suited to Tucson and the low desert. It thrives in full sun to part shade, with a moderate growth rate.
Pentas at a glance
- Water use
- Moderate (established)
- Sun
- Full sun to part shade; in Tucson, afternoon/filtered shade improves performance and reduces heat stress in peak summer. Tolerates more sun with adequate water.
- Mature size
- 1-2 ft tall and wide (dwarf bedding series); larger heirloom types to 3 ft
- Growth rate
- Moderate
- Bloom
- Star-shaped clusters in red, pink, lavender, purple, or white, Spring through fall; near-continuous in warm weather (peaks late spring and through monsoon)
- Cold hardiness
- Frost-tender; damaged below ~40 F and killed by freeze. A tender perennial grown as a summer annual in Tucson (occasionally overwinters in protected microclimates).
- Soil
- Prefers rich, well-drained soil; amend Tucson's lean alkaline soil with compost. Does best with good drainage and organic matter.
- Native range
- Tropical East Africa and Arabian Peninsula (Yemen)
- Best used as
- Butterfly and hummingbird gardens, Mass bedding and borders, Container and patio plantings, Pollinator habitat
- Wildlife
- Outstanding nectar source; strongly attracts butterflies, hummingbirds, and bees. One of the top butterfly-garden annuals for the low desert.
- Toxicity
- Non-toxic to dogs, cats, and humans; not listed by ASPCA as toxic. Safe choice for pet- and child-friendly gardens.
How to grow Pentas in Tucson & the low desert
Watering
Warm-season annual: plant after frost danger (late March-April). Keep soil consistently moist but not soggy; water 2-3x/week in summer heat, more during dry pre-monsoon stretches. Mulch to conserve moisture.
Fertilizer & nutrients
Moderate to heavy bloomer that benefits from regular feeding; apply balanced slow-release fertilizer at planting and supplement with a bloom-boosting (higher-phosphorus) liquid feed every 2-4 weeks during the growing season.
Pruning & care
Deadhead and lightly shear spent flower clusters to promote continuous bloom and bushy growth. Pinch tips of young plants for fullness.
Notes
Reliable warm-season color for Tucson; pair with afternoon shade and steady moisture for best results. Heat-loving and blooms hardest during the monsoon. Often treated as an annual but can persist as a short-lived perennial in frost-free spots.
Sources: University of Arizona Cooperative Extension; Pima County Master Gardeners; Arizona-Sonora Desert Museum