Rosemary in USDA Zone 13 is a perennial Mediterranean herb grown in a tropical zone, and that mismatch is the whole story. Winter lows stay above 60°F and frost never comes, so cold is not a threat — humidity is. Rosemary comes from dry, rocky hillsides around the Mediterranean, where the soil drains fast and the air is dry. In the tropics, heavy rain and humid air can rot its roots and invite disease, and a rosemary plant drowned in a wet Zone 13 summer will die faster than one chilled in a cold winter anywhere else.
Grown the right way, though, rosemary does well in Zone 13 and becomes a long-lived shrub that gives fragrant leaves all year. The secret is drainage: a raised bed, a pot, or a slope, with gritty, fast-draining soil and no wet feet. Give it that, and full sun, and rosemary will reward you for years. Give it heavy, waterlogged soil, and it will not survive the wet season.
Zone 13 at a glance
USDA Zone 13 is the hottest zone in the system, with average winter lows above 60°F, covering tropical places such as Puerto Rico, Hawaii and Guam. It is frost-free all year, so there is no last spring frost and no first autumn frost to plan around. Zone 13 has no frost dates to work from, so plant by heat and by the wet and dry seasons instead. These are zone averages, not promises for any one garden — check your local extension service.
| Detail | Zone 13 guidance |
|---|---|
| Winter low | Above 60°F |
| Frost | Frost-free year-round (no last or first frost dates) |
| Days to germination | 14–28 days |
| Days to maturity | 90–120 days |
| Sowing | start indoors |
| Planting window | Cooler, drier months to establish; perennial once established |
| Harvest | 90–120 days to first light picking; perennial harvest after that |
| Sun | full sun |
| Soil pH | 6.0–7.0 |
| Spacing | 24–36 inches |
| Water needs | low |
| Cold tolerance | tender |
When to plant rosemary in Zone 13
Plant rosemary in the cooler, drier months, so the young plant can establish its roots before the wettest weather arrives. With 90–120 days to a first light picking, a plant set out in the cool season is established and growing strongly by the time the rains build. Avoid planting rosemary at the start of the wettest months, when a young plant can sit in saturated soil for days. Once established, rosemary is a perennial in Zone 13 and needs no replanting — the calendar becomes a pruning calendar instead of a planting one. The planting calendar hub shows the Zone 13 year, and November in Zone 13 is a good start for a new plant.
Starting rosemary in Zone 13
Start rosemary from a young bought plant or a cutting rather than seed: seed germinates slowly in 14–28 days, grows slowly, and does not always come true to variety, while a cutting or a nursery plant gives you a known variety and a year of growth for free. Take cuttings from a healthy plant, strip the lower leaves, and root them in a gritty, free-draining mix kept just moist. Set the young plant out in its final spot and water it in, then water sparingly while it establishes — rosemary roots rot in wet soil far faster than they suffer from a little dryness. A pot is an excellent home for rosemary in the tropics, because you control the drainage completely and can move the plant under cover in the heaviest rain.
Soil, spacing, sun and water
Rosemary grows best in full sun, in poor, gritty, sharply drained soil with a pH of 6.0–7.0. This is the herb where rich soil is a mistake: rosemary in rich, wet soil grows soft, sappy and disease-prone, while rosemary in lean, gritty soil grows woody, fragrant and tough. Mix coarse sand or fine gravel and compost into the planting hole, and use a raised bed or pot where drainage is doubtful. Space plants 24–36 inches apart — a mature rosemary is a shrub, not a small herb — using the plant spacing calculator to plan. Rosemary needs low water once established: water young plants until their roots take hold, then water only when the soil is dry, and water at the base in the morning so the foliage stays dry.
Companion planting
Good companions for rosemary include tomatoes, peppers, marigolds and cabbage, and rosemary is a classic companion for brassicas and beans, partly because its strong scent is said to confuse pests. Thyme is the natural partner, sharing the same love of sun and sharp drainage, and oregano grows the same way in the same dry, sunny corner.
Pests and problems
The common pests to watch for with rosemary are aphids, spider mites and whiteflies. Inspect the foliage regularly, wash aphids off with a strong jet of water, and keep the plant healthy, since spider mites attack dry, stressed plants. The pest identifier helper can help if you are unsure what you are seeing. In Zone 13, the real threat is root rot and fungal disease from wet soil and humid air: leaves turn brown and drop, and the plant dies from the roots up. Sharp drainage, wide spacing for airflow, morning watering at the base and never overwatering are the defences, and a plant in a pot under cover in the wettest weeks often fares better than one in the open ground.
Harvest and storage
Harvest rosemary by snipping sprigs from the tips, starting with a light picking about 90–120 days after planting and taking more as the shrub grows. Never take more than a third of the plant at once, and do not cut into the old woody stems that have no leaves — rosemary does not regrow well from bare wood. Pick in the morning, when the oils are strongest, and use the sprigs fresh or dried. For storage, rosemary dries beautifully: hang small bundles in a dry, airy place out of direct sun, then strip the needles into a jar. It also freezes well. Prune lightly after flowering to keep the shrub compact, and a well-placed rosemary in Zone 13 can live for years, growing bigger and more fragrant with age. Sage is the other woody Mediterranean herb that shares the same dry corner and the same drying routine.
Frequently asked questions
When should I plant rosemary in Zone 13?
In the cooler, drier months, so the young plant establishes before the wettest weather. Once established, rosemary is a perennial and needs no replanting.
Why did my rosemary die in Zone 13?
Almost always wet feet. Rosemary comes from dry, rocky hillsides and its roots rot in waterlogged soil.
What soil and spacing does rosemary need in Zone 13?
Full sun, lean gritty well-drained soil with a pH of 6.0–7.0, spaced 24–36 inches apart.
Should I grow rosemary from seed in Zone 13?
A bought plant or cutting is better.