Nasturtium in Zone 9B — Florida

Nasturtiums are a fantastic addition to any Florida garden. The peppery flavor of the leaves and flowers adds a unique zest to salads, while the seed pods can be pickled for a caper-like treat. Plus, the vibrant blooms attract pollinators and even act as a trap crop for aphids, making them a valuable companion plant in our often pest-prone gardens.

While we face challenges like high humidity and sandy soil here in Florida, the long growing season, approximately 344 days, gives you ample opportunity to enjoy nasturtiums. You can plant in fall, harvest in winter, and even get a spring crop in before the summer heat kicks in.

Starting nasturtium indoors isn't essential in Florida, but it can give you a head start. If you're aiming for an extra-early spring harvest, start seeds indoors from late December through mid January, about four weeks before you plan to transplant. Use seed trays with a good seed starting mix, provide warmth (a heat mat is helpful), and ensure they get plenty of light.

Bottom watering is ideal to prevent damping off. The Florida gardening calendar is different, and starting seeds indoors during this time can help you beat the reversed spring.

Transplant your nasturtium seedlings outdoors from late January through late February. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This prevents shock.

Space the plants 10-12 inches apart to allow for their trailing growth habit. Keep an eye on the weather during this time; we can still get a cold snap, so be prepared to cover them if temperatures dip unexpectedly.

Direct sowing is the preferred method for nasturtiums, as they don't love having their roots disturbed. You can direct sow nasturtium seeds from late January through late October, giving you almost year-round planting opportunities. Choose a sunny spot with well-draining soil.

Prepare the soil by loosening it and removing any weeds. Nasturtiums aren't picky, so don't worry about amending the soil too much. Sow seeds about ½ inch deep and space them 10-12 inches apart. Keep the soil consistently moist until the seedlings emerge.

Nasturtiums thrive in poor, dry soil, so overwatering is a bigger concern than underwatering in Florida. During our typically drier fall and winter months, check the soil moisture about two inches deep using the "finger test." If it feels dry, give them a good watering, aiming for about 1 inch of water per week, depending on rainfall.

In the summer, our wet-summer rainfall pattern often takes care of watering for you. However, during dry spells, monitor the plants and water as needed. Always water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our humid climate.

Yellowing leaves can indicate overwatering, while wilting leaves signal they need a drink. A light layer of pine straw mulch can help retain moisture in the soil and suppress weeds, but don't overdo it – good drainage is key.

You can expect your first nasturtium harvest from late March through late December, about 55 days after planting. The flowers, leaves, and seed pods are all edible. Harvest flowers when they are fully open for the best flavor and visual appeal.

To harvest, gently snip the flowers or leaves with scissors, being careful not to damage the plant. Regularly harvesting encourages continued production, so don't be shy! As our first frost approaches in late December, you can collect any remaining seed pods for pickling and enjoy one last harvest of leaves and flowers before the season ends.

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

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and undersides of leaves. Leaves may be sticky or distorted.
• What causes it: Aphids are attracted to stressed plants and can multiply quickly in warm, humid conditions.
• How to fix/prevent it: Nasturtiums are often used as a trap crop to draw aphids away from other plants. You can also spray them off with a strong stream of water or use insecticidal soap.

Cabbage Caterpillars

• What it looks like: Holes in leaves, often with green droppings nearby. You might see small green caterpillars munching on the foliage.
• What causes it: These caterpillars are the larvae of cabbage white butterflies and can be a nuisance, especially during the cooler months when brassicas are thriving.
• How to fix/prevent it: Handpick caterpillars off the plants or use Bacillus thuringiensis (Bt), a biological insecticide.

Black Fly

• What it looks like: Tiny black flies clustered around new growth, causing stunted growth and distorted leaves.
• What causes it: Black fly thrive in warm, humid conditions and can quickly infest plants.
• How to fix/prevent it: Encourage beneficial insects like ladybugs and lacewings. Insecticidal soap can also be effective, but use it sparingly to avoid harming beneficials.

Florida Specific Challenges: The hot heat, very-high humidity, and wet-summer rainfall in Florida can create ideal conditions for fungal diseases. Ensure good air circulation around your nasturtiums and avoid overhead watering to minimize these issues. Keep a close eye on your plants and address any problems promptly to keep them healthy and productive.

Nasturtiums are great companion plants in Florida gardens. They attract pollinators and beneficial insects while also acting as a trap crop for aphids.

• Tomato: Nasturtiums repel tomato hornworms and whiteflies.
• Cucumber: They help deter cucumber beetles.
• Squash: Nasturtiums help deter squash bugs and vine borers.
• Broccoli & Cabbage: They attract cabbage white butterflies away from your brassicas.

Avoid planting nasturtiums near fennel, as it can inhibit their growth.