Borage is a fast-growing annual herb with star-shaped blue flowers that bees adore, and its young leaves and flowers are edible with a mild cucumber flavour. In Zone 13 it behaves as a short-lived annual that you sow in succession rather than a plant that overwinters, because tropical heat and humidity wear it out quickly. It earns its place in a Zone 13 garden twice over: as a bee magnet and as a companion plant that benefits the vegetables growing beside it. Give it the cooler, drier part of the year and it will flower in about two months from seed. 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
Borage 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.
| 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 | 50–60 days |
| Sowing | direct sow |
| Sun | full sun |
| Soil pH | 6.0–7.0 |
| Spacing | 12–18 inches |
| Water needs | moderate |
When to plant borage in Zone 13
Because Zone 13 is frost-free, you can sow borage in any month, but the best results come in the cooler, drier months when daytime heat is less intense and humidity is lower. Sow a small patch every three to four weeks so you always have young plants coming on as older ones fade. Avoid starting a new sowing in the middle of the wettest, hottest stretch, when seedlings can damp off and mildew spreads fast. Seed sown in the cooler months germinates in 7–14 days and flowers in 50–60 days, so a patch sown at the start of the dry season gives you flowers for most of it. The planting calendar hub gives the Zone 13 picture month by month, and for a cooler-climate comparison see Borage in Zone 11.
Starting borage in Zone 13
Borage is direct-sown: it dislikes transplanting, so sow where it is to grow. Scatter seed about a quarter-inch deep in a sunny bed, keep the soil moist until seedlings appear, and thin to the final spacing once plants have a few true leaves. In Zone 13 the soil is warm all year, so germination is usually at the fast end of the 7–14 day range. Let a few plants set seed at the end of the season and volunteers will appear on their own — borage self-seeds freely in tropical gardens. The seed starting calculator helps you plan succession sowings even without a frost date to anchor them to.
Soil, spacing, sun and water
Borage grows best in full sun, in soil with a pH of 6.0–7.0. It tolerates poor soil better than most herbs, but it does best in soil improved with well-rotted compost, which also helps the bed drain during heavy tropical rain. Space plants 12–18 inches apart — a plant can grow large and sprawling in Zone 13 warmth, so do not crowd it. Afternoon shade is a kindness in the hottest months and can keep plants flowering longer. Test your soil through your local extension service before you amend it.
Borage needs moderate water. Water deeply at the base in the morning so the leaves dry before night, and mulch to keep the soil evenly moist. In the dry season water whenever the top inch of soil feels dry; in the wet season, hold back and let the rain do the work, because soggy soil and wet foliage invite mildew. A raised bed or a mound is worth the effort in Zone 13, where a heavy downpour can waterlog flat ground in minutes. The watering calculator can help you judge how much to give a bed in the dry months.
Companion planting
Good companions for borage include tomatoes, peppers, marigolds and cabbage. Bees drawn to its flowers pollinate the whole bed, and its deep roots bring up nutrients other plants can use. Plant it beside your tomatoes and peppers, and alongside marigolds, which you can read about in our guide to marigolds. The companion planting finder can suggest combinations for your whole bed. Rotate crops each year and avoid planting where the same family (Boraginaceae) grew last year.
Pests and problems
The common pests to watch for with borage are aphids, slugs and cutworms. Inspect plants regularly, especially leaf undersides, and act early: wash aphids off with a strong jet of water and hand-pick slugs after rain. In Zone 13, slugs are worst in the wet season, so keep mulch pulled back a little from stems and clear fallen leaves where slugs hide. Healthy plants in the right soil and spacing resist pests better than stressed ones, and mildew — not insects — is often the bigger threat here, so give plants airflow and morning sun.
Harvest and storage
Pick young leaves and flowers as needed through the flowering period. Flowers are used fresh as a garnish or frozen into ice cubes, and leaves are best young, before the plant gets coarse and hairy. With 50–60 days to maturity, a patch sown in the cooler months flowers well before the wet season peaks. Pick in the morning when the flowers are fresh and open. If a plant starts to look mildewed or exhausted in the heat, pull it and let the next succession sowing take over — that is normal in a tropical garden, not a failure.
Frequently asked questions
When should I plant borage in Zone 13?
Sow in the cooler, drier months for the best results, in succession every three to four weeks. Zone 13 is frost-free, so there is no frost date to wait for — plant by the wet and dry seasons instead.
Does borage come back in Zone 13?
Not as the same plant — borage is an annual — but it self-seeds so freely that volunteers usually appear on their own. Let a few flowers set seed and you may never need to sow it again.
How long does borage take to grow in Zone 13?
Seeds germinate in 7–14 days and the crop takes 50–60 days to maturity. Warm Zone 13 soil usually puts germination at the fast end of that range.
What soil and spacing does borage need in Zone 13?
Borage needs full sun and soil pH 6.0–7.0, spaced 12–18 inches apart. Dig in compost, water deeply, mulch, and test your soil through your local extension service.