Growing Geraniums Outdoors — What to Know

"Geranium" covers two very different groups of plants with very different cold tolerances. Understanding which you have determines what you can safely grow outdoors year-round and what needs protection as temperatures drop.

Hardy geraniums (cranesbills)

True hardy geraniums — the cranesbills — are fully hardy perennials in most temperate climates and can remain in the garden year-round without any protection. They survive frost, freezing temperatures, and wet winters without issue. Varieties like Geranium 'Rozanne', G. pratense, G. psilostemon, and G. macrorrhizum are tough, reliable border plants. Plant them in any reasonably fertile, well-drained soil in full sun to partial shade and leave them to establish. They come back every spring and spread gradually to fill gaps.

Tender pelargoniums outdoors

Pelargoniums sold as bedding geraniums are frost-tender and will be killed by freezing temperatures. In the UK and similar climates, they can safely go outdoors only after the last frost — typically late May or early June. Before planting out, harden them off by placing them outside during the day and bringing them in at night for 7–10 days. They flower from planting until the first autumn frosts, at which point they must be brought back inside or discarded if not overwintering.

• Plant pelargoniums outside after the last frost date.
• Harden off for 7–10 days before planting out.
• Choose a sheltered, sunny position.
• Bring indoors before autumn frosts.

Best outdoor positions

All geraniums perform best in full sun or light shade outdoors. A south-facing bed or patio is ideal for pelargoniums. Avoid exposed windy spots, which can damage flowers and dry out container-grown plants very quickly. Good drainage is critical — both groups struggle in waterlogged soil. Raised beds and free-draining borders suit pelargoniums particularly well. Hardy geraniums tolerate more shade and heavier soils, though they flower more freely in sun.

Rain and wet weather

Extended wet summers can cause botrytis (grey mould) in both groups, particularly on pelargoniums. Good air circulation reduces the risk significantly — avoid planting too densely. Remove dead or dying foliage promptly to reduce the sources of infection. Container-grown pelargoniums can be moved to a sheltered spot during long wet spells if practical.