The genus Penta, species lanceolata, belongs to the Rubiaceae family.
Star flower, Egyptian star flower, star cluster
Grow pentas anywhere as an annual; in growing zones 9 and warmer the plants may perennialize.
Average height is 24-36 inches, but plants that perennialize in frost free zones may reach four feet tall or greater.
Full sun is preferred, although some afternoon shade is tolerated. Plants that receive at least three hours of direct sun will have the best blooms. Pentas that don’t receive enough sunlight will stretch and become leggy.
Penta plants may stay in bloom continuously under ideal growing conditions.
Pentas appreciate a mildly acidic soil pH, in the range of 6.0. Amending the soil with compost or leaf mold can increase the acidity of your soil if it’s on the alkaline side. Many gardeners choose penta transplants to start in the garden, but you can try planting fresh penta seed saved from last year’s flowers, or start softwood cuttings taken early in the growing season. Penta seeds require light to germinate, so don’t cover them with soil.
Pentas need regular irrigation to stay healthy; keep the soil moisture about the same as a wrung out sponge. Pentas tolerate dry conditions, but drought stressed plants are susceptible to spider mite infestations. Avoid regular overhead watering to prevent unsightly brown spots on the foliage.
In frost free growing zones, pentas will exhibit their shrubby nature and begin to grow leggy after one growing season. Prune the plants to six inches in January, when bloom production is at its lowest. After several seasons, the stems of the pentas may become so woody that it’s worth replacing them altogether. When growing as an annual for one season, no pruning is necessary, but regular deadheading will keep the plants blooming productively.
Fertilize pentas once a month with a balanced flower fertilizer during periods of active growth.
- ‘Butterfly’ series: Easy to grow from seed
- ‘Graffiti’ series: Compact mounding plants
- ‘Kaleidoscope Appleblossom’: Pale pink and rose on the same flower; an early bloomer
- ‘New Look’ series: Upright plants that don’t flop
- ‘Northern Lights’: Continues to produce pale lavender flowers in cool temperatures