Geraniums — properly, pelargoniums — are the most popular summer flower in pots, window boxes and hanging baskets, and it is easy to see why: they flower non-stop from late spring until frost, they cope with heat and drought, and they come in red, pink, white, salmon and purple, with scented-leaf types that smell of rose, lemon and mint.
Geraniums are tender perennials, usually grown as annuals in cold zones and overwintered indoors in mild ones. They are started indoors from seed or bought as young plants, and they need sun, free-draining soil and regular deadheading to flower their best. The most common mistake is overwatering: geraniums would rather be a little dry than wet, and wet soil is the fastest way to kill them.
Geraniums at a glance
| Growing factor | What geraniums need |
|---|---|
| Sun | full sun |
| Soil pH | 6.0–7.0 |
| Days to germination | 7–14 |
| Days to maturity | 70–90 |
| Spacing | 12–18 inches apart |
| Water needs | moderate |
| Cold tolerance | tender |
| Family | Geraniaceae |
Starting seeds
Geraniums need a head start indoors — sow under cover and transplant out only after the last frost. Start seeds indoors a few weeks before your last frost date: in Zones 3–5 that means sowing in late winter, in Zones 6–8 early spring, and in Zones 9–10 late winter to very early spring. Zones 11–13 are frost-free, so indoor sowing can happen almost any time, with the cooler months giving the strongest plants; confirm exact timing with your local extension service. Seeds germinate in 7–14 days in warm, moist seed mix. Use clean trays or modules, a fine seed mix, and a bright windowsill or grow lights — leggy seedlings are almost always a light problem, not a seed problem. Harden seedlings off for a week before planting out, moving them outside for lengthening spells each day. Our seed starting calculator works out your indoor sowing date, and the grow light calculator checks whether your setup is bright enough.
Transplanting and planting out
Transplant seedlings out after the last frost, on a cloudy day or in the evening so they do not wilt in the sun. Space plants 12–18 inches apart — that spacing is what keeps air moving and disease down — and water each plant in well. Our plant spacing calculator works out exactly how many plants fit your bed, and the square foot garden planner helps lay them out.
Soil and feeding
Geraniums grow best in fertile, well-drained soil with a pH of 6.0–7.0. Dig in compost before planting — it feeds the soil and helps it hold moisture without getting soggy — and mulch after planting to keep the roots cool and the weeds down. Feed during the growing season with a balanced fertiliser at the label rate, roughly once a month while plants are actively growing, and stop feeding as the season ends. Our fertiliser calculator works out the right amount for your bed, and the compost ratio calculator helps you make good compost to dig in.
Watering
Geraniums have moderate water needs: keep the soil evenly moist while plants are establishing and flowering, and water deeply rather than little and often so the roots grow down. Water at the base in the morning so the foliage dries during the day, mulch to hold moisture in, and watch for wilting in hot, dry spells. Our watering calculator gives a starting point for your bed size, and the watering schedule generator can build a routine around it.
Sunlight and temperature
Geraniums need full sun — at least six hours of direct sun a day. Geraniums are tender — frost kills them or damages them badly, so they are grown as warm-season plants in most zones and planted out only once frosts are over. In frost-free Zones 11–13 they can grow for much of the year. Use the frost date calculator to find your last frost date. Our sunlight calculator can check whether your spot gets enough sun.
Pests and diseases
The pests and diseases to watch for on geraniums are aphids, slugs, cutworms. Aphids can cluster on young growth, slugs may eat young plants, and whiteflies can appear on plants grown under cover. The main disease is grey mould in damp, crowded conditions. Check plants weekly, looking under leaves as well as on top, and act early. Hand-pick larger pests, knock aphids off with a strong spray of water, and remove badly affected leaves. Keep the area weed-free and avoid wetting the foliage when you water, since damp leaves invite fungal disease. Our pest identifier helper can help identify what you are seeing, and the plant disease checker helps narrow down leaf and stem problems.
Companion plants
Good companions for geraniums are lavender, marigolds, garlic, chives. Lavender, marigolds, garlic and chives are good companions, and geraniums pair well with trailing plants in pots and baskets, where they provide the upright colour. Our companion planting finder can suggest more pairings for your bed plan.
Harvesting
Geraniums are grown for flowers, so harvesting means deadheading. Snap off faded flower heads, including the stalk, at least once a week, and the plants will keep producing new blooms until frost. If plants get leggy in midsummer, cut them back by a third and feed them: they regrow and flower again. In autumn, before the first frost, either lift plants and pot them up to overwinter indoors, or take cuttings to root over winter. Our harvest date calculator can estimate your picking date from your sowing date, and the vegetable yield estimator helps you work out how much a bed will produce.
Common problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| Yellow leaves | overwatering | Let the soil dry between waterings and improve drainage. |
| Grey mould on flowers and leaves | damp, crowded conditions | Improve air flow, deadhead regularly, and avoid wetting the foliage. |
| Leggy plants with few flowers | too little light or too much nitrogen | Give full sun and stop feeding. |
Yellow leaves
Yellow leaves on a geranium almost always mean too much water. Geraniums like their soil to dry out a little between waterings, so water only when the top inch is dry, make sure pots drain freely, and never let plants sit in a saucer of water.
Grey mould on flowers and leaves
Grey mould shows as fuzzy grey patches on flowers and leaves, worst in damp, still air. Space plants well, deadhead often, water at the base in the morning, and remove affected flowers and leaves promptly.
Leggy plants with few flowers
A geranium in shade stretches and flowers poorly, and a geranium fed heavily grows leaves instead of flowers. Give them at least six hours of sun, feed only lightly, and pinch young plants to make them branch.
Frequently asked questions
How long does it take to grow geraniums?
From planting to maturity takes 70–90 days. Seed germination takes 7–14 days, and the total time depends on whether you start from seed, a nursery plant, or a bulb or cutting.
How far apart should I plant geraniums?
Space geraniums 12–18 inches apart. That spacing gives each plant room for air movement, which keeps disease down, and room to reach its full size without crowding its neighbours.
What soil pH do geraniums need?
Geraniums prefer a soil pH of 6.0–7.0. Test your soil before amending it — most garden soils are close enough, and guessing with lime or sulphur can do more harm than good.
Can geraniums survive winter?
They are tender, so frost kills them outdoors in most zones. In autumn, lift plants and keep them in a bright, frost-free place over winter, watering only occasionally, or take cuttings in late summer to root indoors.
How often should I water geraniums?
Water when the top inch of soil is dry, and water thoroughly so it runs out of the drainage holes. Geraniums have moderate water needs, but they would rather be slightly dry than wet — overwatering is the most common killer.