Nasturtium in Zone 10A — Florida

Nasturtiums are a fantastic addition to any Florida garden. Their peppery leaves and vibrant flowers add a unique zest to salads, and they attract beneficial insects. Plus, they thrive in our sandy soil and provide a pop of color even when the summer heat starts to fade.

While Florida gardening presents challenges like humidity and nematodes, nasturtiums are surprisingly resilient. With a little planning and attention to timing within our 355-day growing season, you can enjoy a bountiful harvest of these cheerful and useful plants.

Starting nasturtiums indoors isn't essential in our Zone 10A climate, but it can give you a head start. If you choose to go this route, sow seeds indoors from mid December through early January, about four weeks before you plan to transplant. Use seed trays with good drainage and provide warmth and bright light – a sunny windowsill or grow light works well.

When starting seeds indoors, bottom watering helps prevent damping off, a common fungal issue in our humid environment. Simply place the seed tray in a shallow dish of water and allow the soil to absorb moisture from the bottom. Remember, our spring is reversed here in Florida, so getting a jump start indoors helps capitalize on the cooler, drier months.

Transplanting nasturtiums outdoors should happen between mid January through mid February. Before moving them to their final location, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Florida sun and humidity, preventing transplant shock.

Space your nasturtium plants 10-12 inches apart to allow for good air circulation. Keep an eye on the weather forecast – even though we're past our typical frost window, an unexpected cool snap can still occur. Be ready to cover your young plants if temperatures dip unexpectedly.

Direct sowing is the preferred method for nasturtiums, as they don't always love being transplanted. You can direct sow seeds from mid January through late October here in Florida. This wide window takes advantage of our long growing season.

Choose a spot with full sun to partial shade. Prepare the soil by loosening it and removing any weeds. Nasturtiums aren't picky about soil, but good drainage is essential, especially during our rainy season. Sow seeds 1/2 inch deep and 10-12 inches apart. Keep the soil consistently moist until germination, which usually takes about a week. Remember, nasturtiums thrive in poorer soils, so don't over-amend.

Nasturtiums are drought-tolerant and actually prefer slightly dry conditions, which is a blessing in our humid Florida climate. Overwatering is a common mistake that can lead to more leaves than flowers. Adjust your watering schedule based on the season and rainfall.

During our drier spring and fall months, water deeply but infrequently. Use the "finger test" – stick your finger about two inches into the soil. If it feels dry, it's time to water. Aim for about 1 inch of water per week, either from rainfall or irrigation. In the wet summer, you may not need to water at all, unless we're experiencing a dry spell.

Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our humid environment. Avoid overhead watering. Signs of underwatering include wilting leaves, while overwatering can lead to yellowing leaves and root rot. A light layer of pine straw mulch can help retain moisture in the soil and suppress weeds, but don't overdo it.

You can expect your first nasturtium harvest starting around mid March and continuing through late December in Florida. That's a long harvest window! Both the flowers and leaves are edible and have a peppery flavor. Harvest flowers when they are fully open for the best taste and visual appeal.

To harvest, simply snip the flowers or leaves with scissors or your fingers. Avoid pulling or tugging, as this can damage the plant. Regular harvesting encourages continued production, so don't be shy about picking them. The seed pods are also edible and can be pickled for a caper-like treat.

As our brief "winter" approaches in late December, you can still harvest nasturtiums, but growth may slow down. If a frost is predicted, cover your plants to protect them and extend the harvest season.

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

Aphids

• What it looks like: Small, soft-bodied insects clustered on stems and leaves, often accompanied by sticky honeydew.
• What causes it: Warm weather and lush growth. Aphids love the tender foliage, and our mild winters allow them to persist for much of the year.
• How to fix/prevent it: Nasturtiums are often used as a trap crop for aphids, drawing them away from other more valuable plants. You can also blast them off with a strong stream of water or use insecticidal soap.

Cabbage Caterpillars

• What it looks like: Holes in leaves, chewed edges, and green caterpillars feeding on the plant.
• What causes it: Cabbage white butterflies lay their eggs on the leaves, which hatch into voracious caterpillars.
• How to fix/prevent it: Inspect your plants regularly and handpick caterpillars. Bacillus thuringiensis (Bt) is an effective organic control method.

Black Fly

• What it looks like: Tiny black flies swarming around the plant, causing stunted growth and yellowing leaves.
• What causes it: High humidity and poor air circulation. Black flies thrive in damp conditions and can quickly multiply.
• How to fix/prevent it: Improve air circulation by spacing plants properly and pruning dense foliage. Insecticidal soap can also help control infestations.

Florida Specific Challenges: The combination of hot heat, very-high humidity, and wet-summer rainfall can create a breeding ground for fungal diseases and attract pests to nasturtiums. Good air circulation, proper watering techniques, and regular monitoring are essential for keeping your plants healthy. Nematodes can also be a problem in our sandy soil, but nasturtiums are generally nematode-resistant.

Nasturtiums are excellent companion plants in Florida gardens. They attract beneficial insects and can even repel certain pests.

Good companions include tomatoes, cucumbers, and squash, as nasturtiums can help deter squash bugs and other pests that plague these plants. They also do well with broccoli and cabbage, helping to protect them from cabbage white butterflies.

Avoid planting nasturtiums near fennel, as it can inhibit their growth. Otherwise, nasturtiums are generally easygoing and get along well with most garden vegetables.