Rosemary can be grown from seed, but it rewards patience and a little technique. The seeds are slow and erratic, often taking two to four weeks to sprout, and a good share of them may never germinate at all. To give them the best chance, sow plenty of fresh seed 10 to 12 weeks before your last frost, press it onto the surface of a fine seed-starting mix with only a dusting of cover, keep the mix at about 70 to 80°F with bottom heat, and keep it evenly moist but never soggy. Once seedlings appear, give them strong light, airflow and lean, fast-draining soil, then pot them on until they are sturdy enough to plant out. Here is the full process, step by step.
In this guide
Key Takeaways
- Start indoors 10 to 12 weeks before the last spring frost; rosemary seedlings grow slowly.
- Sow more seed than you think you need; germination is low and uneven.
- Surface-sow or cover with no more than about 1/8 inch of fine mix or vermiculite.
- Keep soil at 70 to 80°F with a heat mat; expect sprouts in 14 to 28 days, sometimes longer.
- Seed-grown plants vary in flavor and habit; buy a named variety or take cuttings to clone a favorite.
Why Rosemary Seed Is So Tricky
Rosemary (Salvia rosmarinus, formerly Rosmarinus officinalis) is a Mediterranean shrub, and its seed reflects that origin: small, with a hard coat, and designed to wait for the right moment rather than sprout all at once. That staggered germination works in the wild but frustrates gardeners. Commercial seed is also often older than ideal, and viability falls off with age. Most growers find that only part of a packet comes up, which is why sowing generously is the first rule.
Another quirk: rosemary does not come true from seed. Seed-grown plants can vary in flavor intensity, leaf size, growth habit and cold hardiness. That is why nurseries propagate named varieties such as ‘Arp’, ‘Tuscan Blue’ or ‘Barbecue’ by cuttings. Growing from seed is cheap and fun, and many seedlings turn out excellent, but if you want a specific variety, our guide on how to propagate rosemary from cuttings is the faster route.
What You Need
- Fresh rosemary seed, ideally packed for the current year
- A fine, sterile seed-starting mix (not garden soil or heavy potting soil)
- Cell trays or small pots with drainage, and a humidity dome or clear plastic cover
- A seedling heat mat, ideally with a thermostat
- Grow lights or a very bright south window
- A spray bottle or bottom-watering tray
- Fine vermiculite (optional, for covering seed)
If you have not started seeds indoors before, our guide to seed starting indoors covers lights, trays and timing in detail.
When to Start Rosemary Seeds
Count back 10 to 12 weeks from your average last frost date. Rosemary seedlings take a long time to reach transplant size, so starting late usually means tiny plants going out in early summer.
| Region / zone | Typical last frost | Start seeds indoors |
|---|---|---|
| Zones 3–4 (northern Plains, northern New England) | Mid to late May | Late February to early March |
| Zones 5–6 (Midwest, Northeast, mountain West) | Late April to mid-May | Early to mid-February |
| Zone 7 (transition zone, Mid-Atlantic) | Early to mid-April | Mid to late January |
| Zones 8–9 (South, Pacific Northwest, California) | February to March | November to January, or sow in fall |
| Zone 10 (South Florida, coastal Southern California) | Rare or none | Fall or winter, for planting in the cool season |
Step-by-Step: Sowing Rosemary Seeds
1. Prepare the mix
Moisten seed-starting mix before filling trays; it should feel like a wrung-out sponge. Fill cells or pots and firm lightly so the surface is level. For extra drainage, mix in about one part perlite to four parts seed-starting mix.
2. Optional: soak the seeds
Some growers soak rosemary seed in lukewarm water for a few hours to overnight before sowing to soften the coat. Results are mixed, but it does no harm with fresh seed. Sow soon after soaking; do not let soaked seeds dry out.
3. Sow generously and shallowly
Sow 3 to 5 seeds per cell, or scatter thinly over a small pot. Press them gently onto the surface. Rosemary seed is often described as benefiting from light during germination, so cover very lightly, no more than about 1/8 inch, with fine vermiculite or sifted mix, or leave them just pressed in. Mist the surface to settle the seeds.
4. Add warmth and humidity
Place the tray on a heat mat set so the mix stays around 70 to 80°F, and cover with a humidity dome or plastic wrap. Set the tray under lights or in bright, indirect light. Check daily: the surface should never dry out, but it also should not stay waterlogged. Bottom watering, setting the tray in water for 10 to 15 minutes, keeps the surface undisturbed.
5. Wait, and keep waiting
Expect the first sprouts in about 14 days, with more trickling up over the following two to three weeks. Some seeds may take longer. Do not give up on a tray at three weeks if conditions have been right. If nothing at all has appeared after five or six weeks, the seed was likely not viable; see why seeds don’t germinate for a checklist.
Caring for Rosemary Seedlings
- Light: as soon as most seedlings in a cell are up, remove the dome and move them under grow lights 2 to 4 inches above the leaves for 14 to 16 hours a day. Weak light causes leggy, floppy seedlings.
- Heat: take the tray off the heat mat once seedlings are up; room temperatures of 60 to 70°F give sturdier growth.
- Water: let the surface dry slightly between waterings. Damping-off, a fungal disease that topples seedlings at the soil line, thrives in wet, stagnant conditions.
- Airflow: run a small fan on low nearby to strengthen stems and reduce disease.
- Thinning: when seedlings have their first true leaves (needle-like, unlike the round seed leaves), snip extras at the soil line, leaving the strongest one per cell.
- Feeding: after three to four weeks, feed every two weeks with a quarter-strength balanced liquid fertilizer. Rosemary does not need rich feeding.
Potting Up
When seedlings are 2 to 3 inches tall with several sets of true leaves, move them into 3- to 4-inch pots filled with a fast-draining mix, for example potting mix with about a third perlite or coarse sand. Handle them by the leaves, not the delicate stems. Rosemary grows slowly at first; it is normal for seedlings to be only 3 to 4 inches tall at eight to ten weeks old. Pinching the tip once plants have about six sets of leaves encourages bushier growth.
Hardening Off and Transplanting
Start hardening off about one to two weeks after your last frost, once nights stay above about 45 to 50°F. Set plants outdoors in a sheltered spot for an hour or two the first day, gradually increasing sun and time over 7 to 10 days. Then plant out:
- Full sun, at least 6 to 8 hours a day.
- Sharply drained soil; rosemary rots in heavy, wet clay. Plant on a mound, a slope, a raised bed or in a container.
- Space 2 to 3 feet apart; mature plants can reach 2 to 4 feet tall and wide in mild climates.
- Water regularly the first few weeks, then let soil dry between waterings. Established rosemary is drought tolerant.
Winter Hardiness and Containers
Rosemary is reliably perennial outdoors in roughly zones 8 to 10, and selected cold-hardy varieties survive in zone 7 and sometimes 6 with shelter. Because seed-grown plants vary, assume a seedling has average hardiness. In colder zones, grow it in a pot and bring it indoors before nights drop into the 20s°F, keeping it in a cool, very bright window and watering sparingly through winter. Overwatering and low light, not cold, kill most indoor rosemary; see why rosemary dies for warning signs.
Troubleshooting Rosemary from Seed
| Problem | Likely cause | Fix |
|---|---|---|
| Nothing sprouts after 4 weeks | Old seed, too cold, too deep | Use fresh seed, add bottom heat, surface-sow; wait up to 6 weeks |
| Seedlings collapse at soil line | Damping-off | Water less, add airflow, use sterile mix and clean trays |
| Tall, thin, pale seedlings | Not enough light | Lower grow lights to 2 to 4 inches above leaves |
| Mold on the soil surface | Too wet, no air movement | Remove dome, run a fan, let surface dry slightly |
| Very slow growth after potting up | Normal, or cold, wet roots | Keep warm and bright, let mix dry between waterings |
Harvesting Your First Rosemary
Seed-grown rosemary is usually ready for light harvesting by late summer of its first year. Snip sprig tips a few inches long, never removing more than about a fifth of the plant at once, and cut just above a pair of leaves so it branches. Harvests get much bigger in the second year. For year-round care, pruning and harvesting, see our full guide on how to grow rosemary, browse other long-lived kitchen herbs in our batch guide to perennial herbs, and find more edible-garden projects in the vegetable gardening hub.
Frequently Asked Questions
How long does rosemary take to germinate?
Usually 14 to 28 days at 70 to 80°F, with seeds sprouting unevenly over several weeks. Some may take longer, so keep conditions steady for up to six weeks before giving up.
Should rosemary seeds be covered?
Only very lightly, with no more than about 1/8 inch of fine mix or vermiculite, or simply pressed onto the surface. Burying them deeper reduces germination.
Why is rosemary so hard to grow from seed?
The seed has naturally low and staggered germination, and viability declines with age. Seedlings also grow slowly and are prone to damping-off if kept too wet.
Can I direct sow rosemary outdoors?
It is possible in mild climates once soil is warm, but results are poor because seeds need steady warmth and moisture for weeks. Starting indoors is far more reliable.
Is it better to grow rosemary from seed or cuttings?
Cuttings are faster and produce plants identical to the parent. Seed is cheaper for many plants and fun to try, but plants vary and take longer to reach harvest size.