Pelargonium × domesticum
Pelargonium × domesticum, sold as Regal or Martha Washington geranium, is a cool‑season container type noted for very showy flowers. Plants form upright, somewhat woody stems with medium green leaves. Buds set best with cool nights and bright light. Bloom is concentrated in late spring and early summer in regions with mild weather. Outdoors in hot summers the display is brief. Regals are tender to frost and are grown as annuals or houseplants across most of North America.
At‑a‑glance
- Group/Class: Regal geranium
- Height × spread: 18 to 36 in × 12 to 24 in (45 to 90 cm × 30 to 60 cm)
- Bloom window: Late spring in cool weather; shorter in summer heat
- Color & flower form: Large, ruffled clusters in white, pink, red, purple, burgundy, and bicolors
- Fragrance: 1 trace
- USDA hardiness: Zones 10 to 11; grown as annual or indoor plant elsewhere
- Breeder / Year / Origin: Hybrid group from Pelargonium grandiflorum × P. cucullatum; unknown; Europe
- Pet safety: avoid
How it differs
- Larger, more dramatic flowers but a shorter bloom season than zonal geraniums.
• Requires cool 50 to 60 °F nights to initiate bloom.
• Less tolerant of sustained heat and humidity.
• Best in containers and bright indoor displays.
Strengths
- Striking color range and markings.
• Performs well in bright, cool spring conditions.
• Compact habit suits patios and entries.
• Responds to pinching for a tidy shape.
Care in one minute
- Provide morning sun and bright light; protect from afternoon scorch.
• Use a well‑drained, fertile potting mix and keep evenly moist, not wet.
• Maintain night temperatures near 50 to 60 °F to set buds.
• Feed lightly during active growth.
• Deadhead and pinch after bloom to keep plants compact.
• Overwinter indoors in a bright window; reduce watering in winter.
Watch‑outs
- Flowering stalls in hot, humid summers.
• Frost tender.
• Budworm and botrytis can be problems in crowded, wet conditions.
Best uses (tags)
containers; patio pots; entry displays; seasonal color
Provenance note
Regal geraniums are historic hybrids involving Pelargonium grandiflorum and P. cucullatum that were refined by European breeders for cool‑season display.
References
- Missouri Botanical Garden – Pelargonium × domesticum
- Iowa State University Extension – Martha Washington geraniums and cool‑night requirement
- PlantTalk Colorado – Geranium types and cool‑night note for Regals
- ASPCA – Geranium (Pelargonium species) toxicity to pets
Written by: Your Flowers Guide editorial team
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