Rosemary in Zone 9A — Florida

Rosemary is a fantastic herb to grow here in Florida. Its distinctive flavor enhances so many dishes, plus you can enjoy its fragrance in your garden year-round. The satisfaction of snipping fresh rosemary for your kitchen, especially when you know you grew it yourself despite the Florida heat, is unbeatable.

Our Florida gardening calendar is different, and rosemary can handle it if you give it a good start. We do face challenges like humidity and sandy soil, but with our long growing season (327 days!), you'll find that rosemary thrives if you time things right and give it the conditions it loves.

Starting rosemary from seed indoors is possible, but honestly, it's a bit of a challenge. Rosemary germination can be erratic, and the seedlings grow very slowly. You might want to skip this and just buy a small plant from a local nursery—it'll save you a lot of time and frustration.

If you're determined to try, start your seeds indoors from mid-November through early December. That gives them about 12 weeks to get a head start before transplanting. Use seed trays with a good seed-starting mix and keep them warm and consistently moist. Bottom watering is a good idea to prevent damping off. Remember our spring character is reversed: you're starting these seeds when other gardeners are winding down.

The best time to transplant your rosemary outdoors is from mid-February through early March. Before you move them permanently, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Space your rosemary plants about 24-36 inches apart. This gives them plenty of room to grow. Keep an eye on the weather during this time. We can sometimes get unexpected cold snaps in late winter, so be ready to cover your young plants if a frost is predicted. Honestly, though, buying established plants is the way to go.

Rosemary is drought-tolerant once it's established, which is great for Florida's sandy soil. Overwatering is the biggest mistake people make with rosemary here, especially with our high humidity and wet summers. It prefers dry conditions, so err on the side of underwatering.

During the cooler months (late fall through early spring), water only when the top two inches of soil feel dry to the touch. That's the "finger test." Usually, that translates to about once a week, maybe less. In the hot, humid summer, you might need to water a bit more often, but be careful not to overdo it. Aim for about an inch of water per week, including rainfall. Water at the base of the plant to avoid wetting the foliage too much, which can encourage fungal diseases in our humid climate.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can cause yellowing leaves, root rot, and a generally unhappy plant. Mulch around your rosemary with pine straw or wood chips to help retain moisture in the soil and suppress weeds, but keep the mulch a few inches away from the stem to prevent rot.

Rosemary needs minimal pruning. The main thing is to prune it lightly after it flowers to maintain its shape and encourage bushier growth. Don't cut back into the old, woody stems, as they may not regrow.

Shape your rosemary in the spring after the heaviest flowering is done. Remove any dead or damaged branches at any time. As the first frost approaches around late December, you don't need to do anything special. Just let the plant be and it will continue to grow through the winter.

You can start harvesting rosemary from mid-May through late June, about 90 days after transplanting. Look for 4-6 inch stem tips to harvest. These are the most tender and flavorful parts of the plant.

To harvest, simply snip off the stem tips with a clean pair of scissors or pruning shears. Never take more than about 1/3 of the plant at any one time. This will keep it healthy and productive. Avoid harvesting the woody stems, as they are too tough to eat. Rosemary will continue to produce new growth throughout the growing season, so you can harvest it continuously.

As late December approaches and our first frost is on the horizon, you can still harvest rosemary. The flavor will actually be more intense in the cooler weather. You can dry or freeze any excess rosemary to use throughout the winter.

Here are some common problems you might encounter with rosemary in Florida:

Root Rot from Overwatering

• What it looks like: Yellowing leaves, wilting even when the soil is moist, and a general decline in the plant's health. The roots may be brown and mushy.
• What causes it: Overwatering and poor drainage. Our heavy summer rains combined with Florida's sandy soil that doesn't always drain well can create perfect conditions for root rot.
• How to fix/prevent it: Make sure your rosemary is planted in well-draining soil. Water only when the top two inches of soil are dry. Consider growing rosemary in a raised bed or container to improve drainage.

Powdery Mildew

• What it looks like: A white or grayish powdery coating on the leaves and stems. The leaves may curl, yellow, and eventually die.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity. Surprisingly, dry leaf surfaces actually favor it. Our humid Florida climate can make rosemary susceptible, especially during temperature swings.
• How to fix/prevent it: Improve air circulation around your plants by spacing them properly and pruning them to remove crowded growth. Remove any affected leaves. Neem oil or potassium bicarbonate sprays can help. A milk spray (1 part milk to 9 parts water) is also surprisingly effective.

Spider Mites

• What it looks like: Fine stippling on the leaves (tiny white dots), fine webbing on the undersides of leaves and between stems. Leaves turn bronze or yellow.
• What causes it: Tiny arachnids that thrive in hot, dry conditions. Populations can explode quickly, especially during periods of drought stress.
• How to fix/prevent it: A strong spray of water (daily for a week) is often the best treatment. Increase humidity around your plants. Neem oil or insecticidal soap can also be effective.

Florida Specific Challenges: Rosemary is generally well-suited to Florida, but our hot, humid summers can be a challenge. The very-high humidity makes it prone to fungal diseases like powdery mildew, and our wet-summer rainfall can lead to overwatering and root rot. Be sure to provide good drainage and air circulation to keep your rosemary healthy and thriving. Also, nematodes can be a problem in Florida's sandy soil. Using nematode-resistant varieties can help.

Rosemary has some great companion plants that can help it thrive in Florida. Sage, thyme, and lavender are all excellent choices because they prefer similar growing conditions (full sun and well-drained soil) and can help deter pests. Green beans and carrots are also good companions. Beans fix nitrogen in the soil, which benefits rosemary, and carrots help to break up compacted soil.

Avoid planting rosemary near mint. Mint is very aggressive and can quickly take over a garden bed, outcompeting rosemary for nutrients and water. Plus, mint prefers moist soil, which is the opposite of what rosemary needs.