Catnip is a mint-family perennial famous for the effect it has on cats, but it is also a useful garden herb: its leaves make a calming tea, and its strong scent is said to deter some garden pests. In Zone 13 it grows as a true perennial, since winter lows above 60°F never freeze it back, and a single plant can live and spread for years. That vigour is a warning as much as a benefit — catnip spreads by seed and by creeping stems, so give it a contained spot or a pot unless you want it everywhere. It is one of the easiest herbs to grow in a tropical garden. USDA Zone 13 is the hottest hardiness zone in the United States, covering tropical Puerto Rico and similar frost-free places, with average winter lows above 60°F and no frost at all in an average year. That changes how you plan: there is no last or first frost date to work back from, so you plant by heat and by the wet and dry seasons instead. Frost dates are zone averages and vary by microclimate, elevation and year — check your local extension service.
Zone 13 at a glance
Zone 13 is the hottest hardiness zone in the United States, and catnip has to be planned around heat and rain rather than frost. There is no last frost date to count back from and no first frost date to race against, so the wet and dry seasons do the job that frost dates do in colder zones. Work with that rhythm and catnip will do far better than if you plant by a calendar date alone.
| Detail | Zone 13 guidance |
|---|---|
| Winter low | Above 60°F |
| Frost | Frost-free year-round (no last or first frost dates) |
| Days to germination | 7–14 days |
| Days to maturity | 70–90 days |
| Sowing | both |
| Sun | full sun |
| Soil pH | 6.0–7.0 |
| Spacing | 12–18 inches |
| Water needs | low |
When to plant catnip in Zone 13
Plant catnip at the start of the cooler, drier season, when young plants can establish without the stress of peak heat or pounding rain. Zone 13 is frost-free, so you can set plants out in any month, but the cooler months give the strongest start and the best-flavoured leaves. It takes 70–90 days to reach harvest size from seed, and once established it is a perennial that you cut back and regrow again and again. If you are growing it for cats, start a second plant a few weeks after the first — cats are hard on catnip plants. The planting calendar hub gives the Zone 13 picture month by month, and for a cooler-climate comparison see Catnip in Zone 11.
Starting catnip in Zone 13
Catnip can be started indoors or sown directly. Seed germinates in 7–14 days in warm soil; chilling seed in the fridge for a few days before sowing can improve germination. Sow shallowly, keep the soil moist until seedlings appear, and thin to the final spacing. Plants started indoors should be hardened off for a week before going out. The simplest approach in Zone 13 is a nursery plant in a container: it establishes fast, stays contained, and can be moved into afternoon shade in the hottest months. The seed starting calculator helps you plan sowings for the cooler months.
Soil, spacing, sun and water
Catnip grows best in full sun, in soil with a pH of 6.0–7.0. It tolerates poor, sandy soil better than most herbs and actually produces stronger-scented leaves in lean soil, so do not over-feed it. Space plants 12–18 inches apart, and give it sharp drainage — a raised bed or a pot with drainage holes suits Zone 13's heavy rains. A plant in rich, wet soil grows lush and weak and is more likely to rot. Test your soil through your local extension service before you amend it.
Catnip needs low water once established — it is drought-tolerant and dislikes wet feet, which matters in a zone where the wet season can drown a bed. Water young plants regularly until their roots take hold, then water only when the soil is dry a couple of inches down. Water at the base in the morning and keep mulch light and pulled back from the crown, so the plant stays dry around its base. In a container, let the mix dry between waterings. The watering calculator can help you avoid over-watering in the wet season.
Companion planting
Good companions for catnip include tomatoes, peppers, marigolds and cabbage. Its scent is said to deter flea beetles and aphids, which is why gardeners often plant it at the corners of a vegetable bed — but keep it in a pot sunk into the bed if you do, or it will spread into the rows. A related Zone 13 herb guide is stevia, another perennial herb for a frost-free garden. The companion planting finder can suggest combinations for your whole bed. Avoid planting where the same family (Lamiaceae) grew last year.
Pests and problems
The common pests to watch for with catnip are aphids, spider mites and whiteflies. Spider mites are the main Zone 13 problem: they thrive in hot, dry weather and show up as fine webbing and speckled leaves, so hose plants down regularly in the dry season. Aphids can be washed off with water. The biggest pest of all is often the neighbourhood cats, which roll on young plants and flatten them — protect new plants with a wire cage or a ring of sticks until they are bushy enough to take it.
Harvest and storage
Begin harvesting leaves once the plant is well established, about 70–90 days after sowing. Pick in the morning and cut stems just above a leaf joint, which encourages branching. Leaves can be used fresh, or dried in a shady, airy place and stored in a sealed jar — dried leaves keep their scent for months. For cats, offer a small pinch of dried leaf; a little goes a long way. Cut the whole plant back by a third after flowering and it will regrow quickly in Zone 13 warmth.
Frequently asked questions
When should I plant catnip in Zone 13?
Plant at the start of the cooler, drier season for the strongest start. Zone 13 is frost-free, so there is no frost date to wait for — plant by the wet and dry seasons instead.
Is catnip a perennial in Zone 13?
Yes. With winter lows above 60°F and no frost, catnip lives for years outdoors in Zone 13, and it spreads, so a container or a contained spot is wise.
How long does catnip take to grow in Zone 13?
Seeds germinate in 7–14 days and plants take 70–90 days to reach harvest size. A nursery plant is harvestable much sooner.
What soil and spacing does catnip need in Zone 13?
Catnip needs full sun and well-drained soil at pH 6.0–7.0, spaced 12–18 inches apart. It prefers lean soil and low water once established.