How to Grow Rosemary From Seed

Rosemary is a tender Mediterranean perennial, and it is famously slow and unpredictable from seed, so give yourself plenty of lead time. Start seeds indoors 10 to 12 weeks before your last spring frost, since they can take several weeks just to sprout. Wait to move seedlings outside until all danger of frost has passed and the soil has warmed. In warm zones 8 and above, rosemary can stay outdoors year-round; in colder areas, grow it in a pot you can bring inside for winter.

Set your expectations first: rosemary seed is slow to sprout and often has a low germination rate, so sow more seeds than you think you need and be patient. Press the small seeds lightly onto the surface of a fine, well-drained seed-starting mix and barely cover them, no more than an eighth of an inch, since they need light and warmth. Keep the mix at a steady 70 to 75F, ideally on a heat mat under a dome, and lightly moist but never soggy. Germination usually takes 2 to 4 weeks and can stretch to 6. Once seedlings are a few inches tall, pot them up, then plant out 24 to 36 inches apart in full sun and sharply drained soil.

Rosemary is tough and drought-tolerant once it is established. Give it full sun, gritty well-drained soil, and only water when the top inch dries out, as it hates soggy roots far more than dry ones. It needs little to no feeding. Prune lightly through the season to keep it bushy and to harvest, but avoid cutting hard into old bare wood. Climate is the deciding factor with rosemary: it is reliably perennial outdoors only in about USDA zone 8 and warmer, so gardeners in California, Texas, Florida, and the coastal Southeast can grow it into a large woody shrub in the ground. North of that, in the Midwest, Northeast, and mountain states, hard winters kill it outdoors, so grow it in a pot and move it to a cool, bright indoor room before the first hard frost.

Rosemary is a classic garden helper: its strong aroma confuses and deters cabbage moths, carrot flies, and bean beetles, while its flowers feed bees. It grows best beside other sun-loving, dry-soil plants. These four make especially good companions, and you can add any of them in one click:

You can begin snipping sprigs once the plant is established and growing well, usually in its second season from seed. Cut 4 to 6 inch tips as you need them, taking no more than a third of the plant at once so it keeps its shape and vigor. Harvest is best in the morning, and regular light cutting actually encourages fuller, bushier growth. Strip the needle-like leaves from the woody stems for the kitchen, or dry whole sprigs by hanging them in a warm, airy spot.

Use rosemary's piney, resinous flavor where it can stand up to strong food: tuck whole sprigs under roast chicken, lamb, and potatoes, strip and chop the leaves finely into bread and focaccia dough, or steep a sprig in warm olive oil for a finishing drizzle. Because the leaves stay tough, chop them small or pull the sprig before serving. The bare woody stems make aromatic skewers for the grill. In the garden the small blue flowers draw bees, and a pot by the door stays green and fragrant year-round.

• Poor, slow germination: this is normal for rosemary. Sow extra seed, provide steady warmth of 70 to 75F and light, and wait up to 6 weeks.
• Root rot: caused by heavy, wet soil. Grow rosemary in gritty, sharply drained ground or pots and let it dry between waterings.
• Powdery mildew indoors: give potted rosemary bright light and good airflow, and avoid crowding and overwatering.
• Winter loss in cold zones: rosemary is not reliably hardy below zone 8, so pot it up and overwinter it in a cool, bright room.