Starting geraniums from seed indoors is a project that rewards a little patience, and this guide walks you through it from the first seed to a plant that is ready for the garden. Geranium seeds — the seed-raised bedding geraniums, not the zonal types grown from cuttings — are slow to start and need warmth. They germinate in 7–14 days in warm mix, sown about an eighth of an inch deep. The seedlings are small and slow for the first month, which is why geraniums need one of the longest indoor starts of any flower: 10–12 weeks before your last frost. Do not be discouraged by slow early growth — once geraniums size up they are tough, drought-tolerant plants that flower all summer. Use fresh seed, since geranium seed loses viability faster than most flower seed.
Geraniums belong to the Geraniaceae family, need full sun, and grow best in soil with a pH of 6.0–7.0. Seeds take 7–14 days to germinate, plants take 70–90 days to reach maturity, they are tender — frost will damage or kill it, and they are usually spaced 12–18 inches apart.
Geraniums at a glance
| Growing factor | What geraniums need |
|---|---|
| Days to germination | 7–14 |
| Sowing method | start indoors |
| Days to maturity | 70–90 |
| Soil pH | 6.0–7.0 |
| Spacing | 12–18 inches apart |
| Sun | full sun |
| Cold tolerance | tender |
When to start geraniums seeds indoors
The short answer: start geraniums seeds indoors 10–12 weeks before your last frost.
Geraniums are tender and slow, so start early. In Zones 3–5, sow indoors in mid- to late winter; in Zones 6–8, sow in late winter; in Zones 9–10, sow in late winter so plants are ready for spring. In frost-free Zones 11–13, you can start geraniums for much of the year; check your local extension service for the best local window. Because geraniums need 10–12 weeks indoors, this is a crop where the calendar really matters — sow too late and you lose a month of flowers. Use our seed starting calculator to work out your sowing date, and the frost date calculator to find your last frost.
Frost dates vary by microclimate, so confirm your dates with your local extension service, and use the last first frost lookup to check your own frost dates before you sow.
What you need
- Fresh geraniums seed — check the packet date; test old seed with the seed viability checker.
- Seed starting mix — fine, sterile and free-draining. Do not use garden soil.
- Containers — cell trays, small pots or soil blocks, cleaned before use.
- A tray and a clear lid — to hold humidity until germination.
- Labels and a marker — you will not remember what you sowed in three weeks.
- A spray bottle — for gentle watering that does not wash small seeds away.
- A grow light — a sunny windowsill is rarely enough. Our grow light calculator helps you set it up.
- Potting mix for potting on — seedlings outgrow seed mix once they have true leaves.
Step by step: starting geraniums seeds indoors
- Fill containers with damp seed mix. Moisten the mix first — it should feel like a wrung-out sponge. Fill to just below the rim.
- Sow the seed. Sow one seed per cell, about an eighth of an inch deep, and cover lightly with mix. Use fresh seed — geranium seed loses viability fast — and keep the pots warm.
- Label everything. Write the crop and the sowing date on the label now, not later.
- Cover to hold humidity. Put a clear lid or cling film over the tray so the surface stays moist.
- Keep warm and wait. Geraniums seeds take 7–14 days to germinate — do not throw the tray away after a week. The germination time calculator gives you a realistic window.
- Remove the cover as soon as seedlings appear. A closed, humid tray is where damping off starts.
- Give light immediately. Move the tray under a grow light or to your brightest window, with the light 2–3 inches above the leaves.
- Water from below. Stand the tray in a shallow dish of water, let the mix soak it up, then drain.
- Thin to one seedling per cell. Snip the weaker seedling off at soil level — do not pull it out, or you will disturb the roots of the one you keep.
- Pot on when the roots fill the cell. Once seedlings have two sets of true leaves, move each one into a larger pot of potting mix. Handle seedlings by their leaves, never by the stem.
Light for seedlings
Light is the single biggest difference between sturdy seedlings and leggy ones. A windowsill that looks bright is often far too dim for a seedling, because glass cuts light and late-winter days are short. Give geraniums seedlings 14–16 hours of light a day from a grow light hung 2–3 inches above the leaves, raising it as the plants grow. Our grow light calculator helps you set it up. Seedlings that stretch tall, pale and thin need more light — move the light closer at once.
Watering seedlings
Geraniums have moderate water needs. Keep the mix evenly moist, never soggy and never bone dry: check daily by touching the surface, and water if it feels dry. Water from below when you can, by standing the tray in a shallow dish for ten minutes and then draining it, so the surface stays dry and the roots grow down. Our watering calculator gives a starting point for amounts. Use room-temperature water and water in the morning. The two mistakes that cause most seedling losses are overwatering, which rots roots and invites damping off, and letting trays dry out completely, which kills fine roots in hours.
Hardening off
Hardening off is the week of gradual exposure that turns a soft indoor seedling into a plant that can survive outdoors. Start 7–10 days before planting out: put seedlings outside in a sheltered, shady spot for an hour or two on day one, then leave them out a little longer each day, with more sun and wind, until they spend full days outside. Do not leave them out overnight until the last couple of days, and bring them in if frost is forecast — geraniums are tender, so a frosty night can undo weeks of work.
Transplanting outdoors
Geranium seedlings are small for a long time, so do not rush them out. Wait until all frost danger has passed and the seedlings are sturdy, then harden off and plant out in full sun, spacing plants 12–18 inches apart in soil with a pH of 6.0–7.0. Water in gently and do not overwater afterwards — geraniums prefer to dry out a little between waterings. They flower in 70–90 days from seed, so a plant started 10–12 weeks indoors will be close to flowering when it goes out. Our plant spacing calculator works out your layout, and the companion planting finder suggests neighbours — lavender, marigolds, garlic and chives all grow well with geraniums.
Transplant on a cloudy day or in the evening, water each plant in well, and mulch lightly around the base. Check daily for the first week — a seedling's roots are still shallow.
Common problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| Seeds never sprout | Old seed, or pots too cool | Use fresh seed and keep pots warm — check viability with the seed viability checker |
| Seedlings grow very slowly | Normal for geraniums — they are slow for the first month | Be patient, keep them warm and bright, and do not overfeed |
| Damping off | Soggy mix, still air | Water from below, ventilate, and use fresh sterile mix |
| Leggy seedlings | Too little light | Grow light 2–3 inches above the leaves from the day they sprout |
Watch for pests once plants are outdoors: the common pests of geraniums are aphids, slugs, cutworms. Check plants weekly, looking under leaves as well as on top, and act early. Our pest identifier helper can help identify what you are seeing, and the plant disease checker helps narrow down leaf and stem problems.
Seeds that never germinate
Geranium seed loses viability faster than most flower seed, so old seed is the usual culprit.
Painfully slow seedlings
Geranium seedlings look like they are doing nothing for the first few weeks — a pair of small leaves that barely grow.
Damping off
Geranium seedlings are soft and slow, which makes them easy victims for damping-off fungi in wet, still air.
Frequently asked questions
How long do geranium seeds take to germinate?
Geranium seeds take 7–14 days to germinate in warm, moist mix. Use fresh seed and keep the pots warm.
When should I start geranium seeds indoors?
Start geranium seeds indoors 10–12 weeks before your last frost. They are slow growers and need the long head start.
Can I direct sow geraniums?
It is not recommended. Geranium seeds are slow and need warmth and a long season, so direct-sown plants flower very late. Indoor starting is the normal method.
Are seed geraniums the same as zonal geraniums?
Not exactly. Seed-raised geraniums are bedding types grown from seed; zonal geraniums are usually grown from cuttings to keep the variety exact. Both flower well, but seed types are cheaper and easier to start in bulk.