Hardiness zones
Sunset All zones as annual, 23-24 as perennial
USDA All zones as annual, 11 as perennial
Landscape Use: Summer annual bedding plant, edging, accent, container plant
Form & Character: Formal and festive, refined
Growth Habit: Cold sensitive herbaceous perennial grown as annual in Phoenix area. Moderate growth rate to 2' maximum in our area.
Foliage/Texture: Ovate to lanceolate leaves with prominent pinnate patterns of venation, medium to dark green, medium texture.
Flowers & Fruits: Umbellate clusters of pink small, white, lilac or red flowers, each cluster to 4" in diameter; fruit inconspicuous.
Seasonal Color: Blooms all summer, but most heavily in May and June.
Temperature: Surprisingly heat loving, but intolerant of temperatures below 40oF.
Light: Full sun to partial shade
Soil: Rich, organic soil (high water and nutrient holding capacity) that is well drained
Watering: Star clusters requires frequent moderate amounts of water to grow in Phoenix during the summer.
Pruning: Remove dead or old flower clusters as they are born terminally and apically in umbellate clusters.
Propagation: Seed
Disease and pests: None, because star clusters is a short lived annual plant in Phoenix landscapes.
Additional comments: Star clusters is a decent summer annual for landscape flower beds and borders in mesic and oasis designs in the Phoenix area. Its also a nice container pot plant and may also be used as a cut flower. Star clusters is not a good choice for arid or desert landscapes themes. There are many named cultivars of different flower colors including 'Butterfly Blush'.
