When to Plant Rosemary

Spring planting in frost areas

Rosemary is half-hardy: a healthy plant can take a light freeze, Texas A&M notes, but young transplants set out into cold, wet spring soil get off to a poor start. The safe window opens when the danger of frost has passed, which for most gardens means from your average last frost date to about two weeks after it. The dates for your zone above show that window for your area.

In heavy or poorly drained soil, waiting until the soil has dried out from spring rains matters more than the calendar date, because wet roots are what kill rosemary.

Spring is also the time to move overwintered pots back outside. Wait until after the last frost, as Penn State advises.

Fall planting in mild-winter areas

Where winters stay mild, fall is often the better season, because roots establish during cool weather before summer heat arrives.

In the low desert, University of Arizona recommends planting rosemary in October or November in Tucson. Summer planting there is hard on new plants; if you must plant then, watch watering closely, since potted herbs may need water twice a day.

In Florida, UF/IFAS calendars list rosemary for late spring and late summer: April-June and August-September in North Florida, and May-June and August-September in Central and South Florida. The August entries specify using plants rather than seed. Rosemary then grows year-round, though plants in the colder parts of the state may need freeze protection.

In zone 7 and colder, avoid fall planting in the ground. A new plant has not had time to root deeply, and Oregon State notes that older, established plants are the hardiest. Plant in spring and give it a full season before its first winter.

Starting from seed or cuttings

Most gardeners skip seed. Texas A&M reports germination of only about 15 percent, and Penn State notes that named varieties do not come true from seed. If you want to try, Illinois Extension’s general herb schedule is to sow indoors about 10 weeks before transplanting, roughly March sowing for May planting in Illinois. Expect about 15 months from seed to a harvestable plant, versus about 3 months from a nursery plant.

Cuttings can be timed to your planting date. Texas A&M’s method, using 3-inch tips in small pots at 60 to 70°F, gives rooted plants in about 8 weeks. Penn State’s method, using 6-inch tips with rooting hormone and 70 to 75°F bottom heat, roots in 10 to 20 days. Take cuttings in late winter for spring planting, or in summer for fall planting in warm regions.

Timing the move indoors in fall

Where rosemary will not survive winter outdoors, the important fall date is when you bring it in. Penn State recommends 2 to 3 weeks before your first fall frost. Don’t wait for the first cold snap to force the move. Put it in a south- or west-facing window or under grow lights, in a cool room, and water carefully all winter.

Quick guide by region

• Cold north (zones 3-6): plant in spring after the last frost, in a pot you can bring indoors, or grow as an annual. Hardier cultivars such as ‘Arp’ and ‘Madalene Hill’ can survive zone 6b with protection, per Penn State.
• Zone 7 and the mid-South: plant hardy cultivars in spring after frost in a well-drained, sheltered spot.
• Humid Southeast and Florida: late spring or late summer; plant in raised beds.
• Desert Southwest: October-November, with afternoon shade planned for summer.
• Zones 9-10 elsewhere: spring or fall both work; avoid planting into soggy winter soil.