Marigolds are the workhorse flower of a Zone 13 garden: they grow fast, flower for months, and thrive in tropical heat that defeats many other flowers. They are also the most useful flower you can plant, because their roots and scent help keep soil pests down, which is why they appear as a companion in almost every vegetable guide. In a frost-free zone you can grow them all year, sowing a new round every few weeks for continuous colour. They ask for little — sun, drainage and a little water — and give back far more than they take. 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 marigolds 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 marigolds 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 | 5–10 days |
| Days to maturity | 45–60 days |
| Sowing | both |
| Sun | full sun |
| Soil pH | 6.0–7.0 |
| Spacing | 8–12 inches |
| Water needs | moderate |
When to plant marigolds in Zone 13
Sow marigolds in any month in Zone 13, since the zone is frost-free and the soil is always warm. The best results come in the cooler, drier months, when flowers last longest and mildew is least likely, but marigolds will grow in the wet season too if the bed drains well. Seed germinates in 5–10 days and plants flower in 45–60 days, so a sowing today gives you colour in about seven weeks. Sow a small patch every three to four weeks for continuous flowers, and let a few plants set seed for volunteers. The planting calendar hub gives the Zone 13 picture month by month, and for a cooler-climate comparison see Marigolds in Zone 10.
Starting marigolds in Zone 13
Marigolds can be started indoors or sown directly; direct sowing is simplest in Zone 13, where the soil is warm all year. Sow seed a quarter-inch deep, keep the soil moist until seedlings appear, and thin to the final spacing once plants have a few true leaves. Plants started indoors should be hardened off for a few days before going out. For the quickest colour, buy nursery plants in flower — they establish fast and fill a gap in a bed at once. The seed starting calculator helps you plan succession sowings through the year.
Soil, spacing, sun and water
Marigolds grow best in full sun, in soil with a pH of 6.0–7.0. They tolerate poor soil better than most flowers, but they flower best in soil improved with compost, and they need sharp drainage — a waterlogged bed in the wet season will rot them. Space plants 8–12 inches apart; French marigolds stay compact, while African marigolds grow taller and need more room. Deadhead spent flowers regularly to keep plants blooming. Test your soil through your local extension service before you amend it.
Marigolds need moderate water. Water at the base in the morning so the leaves dry before night, and mulch lightly 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 and rot. A raised bed helps in Zone 13, where a heavy downpour can waterlog flat ground in minutes. The watering calculator can help you judge amounts in the dry months.
Companion planting
Good companions for marigolds include tomatoes, peppers, cucumbers, squash and beans — marigolds are the classic companion flower, planted at the edges of vegetable beds to help with soil pests and to draw pollinators. They are especially useful beside tomatoes and peppers, and they look good with zinnias, another Zone 13 flower that thrives in the heat. The companion planting finder can suggest combinations for your whole bed. Rotate crops each year and avoid planting where the same family (Asteraceae) grew last year.
Pests and problems
The common pests to watch for with marigolds are aphids, whiteflies and slugs. Aphids cluster on new growth and can be washed off with water, and whiteflies rise in a cloud when plants are disturbed in hot, dry weather — hose plants down and keep them watered. Slugs are worst in the wet season, so keep mulch pulled back a little from stems. In Zone 13, mildew in humid weather is often a bigger problem than insects: give plants airflow, water at the base, and remove badly affected leaves.
Harvest and storage
Marigolds are not harvested for the kitchen in the usual sense, but their flowers are the harvest: pick them for the vase, deadhead spent blooms to keep plants flowering, and cut whole plants at the end of their run. With 45–60 days to maturity, a sowing flowers for months in Zone 13 if you deadhead it. Pick flowers in the morning when they are fresh and open. At the end of the season, dig spent plants into the bed — marigold roots are said to help the soil — and save seed from a few flowers for the next sowing.
Frequently asked questions
When should I plant marigolds in Zone 13?
Sow in any month — Zone 13 is frost-free with warm soil all year. The cooler, drier months give the longest-lasting flowers, and succession sowings every few weeks keep colour going.
Do marigolds grow well in Zone 13?
Yes — they are heat lovers that thrive in tropical warmth and flower for months. They also help with soil pests, which makes them the most useful flower in a Zone 13 garden.
How long do marigolds take to flower in Zone 13?
Seeds germinate in 5–10 days and plants flower in 45–60 days. Deadheading keeps them blooming for months.
What soil and spacing do marigolds need in Zone 13?
Marigolds need full sun and well-drained soil at pH 6.0–7.0, spaced 8–12 inches apart. Test your soil through your local extension service.