Flowers

How to Plant Pentas: Timing, Spacing, Care & Bloom

Quick answer

Start indoors 8–10 weeks before last frost (NC). Transplant after frost threat (ISU). Perennial only in zones 10–11 (NC).

Pentas at a glance

PlantStart indoors: 10–8 wk before last frost; Transplant: last frost
SunFull sun for best bloom (NC/ISU/UF); well-drained soil; water consistently, allowing some drying between waterings (NC).
WaterFull sun for best bloom (NC/ISU/UF); well-drained soil; water consistently, allowing some drying between waterings (NC).
SpacingNC: available space 12 inches–3 feet.
Days to bloomBloom spring–fall
-11-10-9-8-7-6-5-4-3-2-1LF+1+2+3
■ Start indoors   ■ Plant out   ■ Harvest
Weeks relative to last frost (LF). Colored weeks show when our ZIP planner schedules each step.
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Updated

Annual north of zone 10: NC State — perennial in zones 10–11; elsewhere treat as a bedding annual or houseplant.

Pentas plant
Pentas (Pentas lanceolata). Photo: Md. Siddiq Hasan, Wikimedia Commons, CC BY-SA 4.0 (resized).

Sourced from university extension guides. For dates where you live, use the ZIP planting planner.

Planting timing

NC State: seed started indoors 8 to 10 weeks before last frost date. (NC State Pentas lanceolata) Iowa State: in northern zones set plants out after the threat of frost has past. ISU’s “16 weeks or more” to garden size is lead time to size — not a frost-week start rule. (ISU pentas)

Depth and spacing

NC: available space 12 inches–3 feet. UF: many about 2–3 feet tall; leave room in beds.

Sun, soil and water

Full sun for best bloom (NC/ISU/UF); well-drained soil; water consistently, allowing some drying between waterings (NC).

Care and bloom

Pinch tips; deadhead spent clusters (ISU). Star clusters spring into fall; butterflies and hummingbirds (NC/ISU/UF).

Pests and diseases

NC: spider mites, aphids; caterpillars may chew leaves — water spray or soap as labeled.

Related: ZIP planner · planting calendars

Frequently asked questions

When do I start seed?

8–10 weeks before last frost (NC).

When outside?

After frost threat (ISU).

Perennial?

Zones 10–11 (NC); annual elsewhere.

Sources