Nasturtium in Zone 9A — Florida

Nasturtiums are a fantastic addition to any Florida garden. Their peppery flavor adds a zing to salads, the bright flowers are edible and beautiful, and they’re surprisingly easy to grow here. Plus, they can act as a trap crop for certain pests, drawing them away from your more vulnerable veggies.

Our Florida gardening calendar is different, and summer is definitely the slow season. But with a 327-day growing season, you have plenty of time to enjoy nasturtiums. Timing is key to avoid the worst of the heat and humidity that can lead to fungal issues.

Starting nasturtiums indoors isn't usually necessary in our Zone 9A Florida climate, as they prefer direct sowing. However, if you're eager to get a head start, you can start seeds indoors early to late January, about four weeks before our typical last frost.

Use seed trays with a good seed-starting mix, and keep them in a warm spot with plenty of light. Bottom watering is a great technique to keep the soil consistently moist without overwatering, which is especially important in our humid climate. Remember, our spring is reversed; starting too early can lead to leggy seedlings that struggle once transplanted.

Transplanting nasturtiums outdoors should be done early February through early March, after any threat of frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Space them about 10-12 inches apart in well-draining soil. Keep an eye on the weather forecast; a sudden cold snap could set them back.

Direct sowing is the preferred method for nasturtiums, as they don’t love having their roots disturbed. You can direct sow seeds early February through mid October in Florida.

Choose a spot with full sun to partial shade, and prepare the soil by loosening it and removing any weeds. Nasturtiums aren't picky about soil, but good drainage is essential. Sow seeds about ½ inch deep, spacing them 10-12 inches apart. Keep the soil consistently moist until germination, which usually takes about a week.

Nasturtiums are drought-tolerant and actually thrive on neglect, which is perfect for Florida's sometimes-unpredictable weather. In general, less is more when it comes to watering.

During our drier spring and fall months, check the soil moisture with the finger test – stick your finger about 2 inches deep into the soil. If it feels dry, give them a good watering, aiming for about 1 inch of water per week, including rainfall. Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our humid environment. During our wet summer months, you likely won't need to water at all unless we're experiencing a dry spell. Overwatering can lead to yellowing leaves and root rot, while underwatering will cause the leaves to wilt and the plant to stop flowering. Mulching around the base of the plants with pine straw or wood chips can help retain moisture in the soil and suppress weeds.

You can expect your first harvest of nasturtium flowers and leaves early April through late December, about 55 days after planting. Both the flowers and leaves are edible and have a peppery taste.

Harvest flowers when they are fully open, ideally in the morning when their flavor is most intense. Simply snip them off the stem with scissors or your fingers. For the leaves, harvest them as needed, taking care not to remove too many from one plant at a time. To encourage continued production, regularly harvest the flowers and leaves, as this will prevent the plant from going to seed too quickly. As our first frost approaches in late December, you can collect the seed pods to pickle them or save them for planting next 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 and sooty mold.
• What causes it: Aphids thrive in warm, humid conditions, making them a common pest in Florida gardens. They are attracted to stressed plants.
• 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: Green caterpillars that chew holes in leaves, leaving behind droppings.
• What causes it: Cabbage white butterflies lay their eggs on nasturtium leaves, and the caterpillars hatch and feed on the foliage.
• How to fix/prevent it: Handpick the caterpillars off the plants, or use Bacillus thuringiensis (Bt), a natural insecticide that is effective against caterpillars.

Black Fly

• What it looks like: Tiny black flies that cluster around new growth.
• What causes it: Black fly are attracted to new growth.
• How to fix/prevent it: Spray with insecticidal soap.

Florida Specific Challenges: The combination of hot heat, very-high humidity, and wet-summer rainfall can create conditions favorable for fungal diseases on nasturtiums. Ensure good air circulation around the plants, avoid overhead watering, and consider using a fungicide if necessary.

Nasturtiums make great companions for many vegetables in Florida gardens. They attract pollinators and beneficial insects, and can also act as a trap crop for aphids, protecting other plants.

Good companions include tomatoes, cucumbers, squash, broccoli, and cabbage. They help tomatoes by repelling certain pests that commonly attack them. Cucumbers and squash benefit from the added pollination provided by the nasturtiums. Broccoli and cabbage are less likely to be targeted by cabbage white butterflies when nasturtiums are nearby. Avoid planting nasturtiums near fennel, as they can inhibit each other's growth.