Nasturtium in Zone 6A — Southeast

Nasturtiums are a fantastic addition to any Southeast garden. The peppery flavor of the leaves and flowers adds a unique zest to salads, and the vibrant colors brighten up any dish. Plus, they're incredibly easy to grow and attract beneficial insects to your garden, making them a valuable and beautiful addition.

Our long growing season here in the Southeast gives you plenty of time to enjoy nasturtiums, even with the challenges of our hot, humid summers and clay soil. With a growing season that stretches nearly 200 days, you can easily work around potential issues like disease pressure and Japanese beetles.

While nasturtiums thrive when direct sown, starting them indoors can give you a head start, especially if you're eager for early blooms. You'll want to begin around mid-March through early April, giving you about four weeks to get them ready for transplanting after the last frost.

Use seed trays filled with well-draining potting mix. Keep the trays in a warm location with plenty of light – a sunny windowsill or under grow lights works great. Remember to water from the bottom to avoid damping off, which can be a problem with our moderate spring humidity.

Once the danger of frost has passed, usually around mid-April through mid-May, it's time to transplant your nasturtium seedlings outdoors. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Southeast's fluctuating spring temperatures.

Plant your seedlings 10-12 inches apart in well-draining soil. Keep an eye on the weather forecast – a late cold snap can still happen, so be prepared to cover them if necessary.

Direct sowing is the preferred method for nasturtiums, as they don't always love being transplanted. You can direct sow from mid-April through mid-August, giving you a long window to get them in the ground.

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 key. Sow seeds about ½ inch deep and 10-12 inches apart. Keep the soil consistently moist until the seedlings emerge, which usually takes about a week or two.

Nasturtiums are surprisingly drought-tolerant and actually prefer drier conditions, making them a great choice for our sometimes unpredictable Southeast weather. The key is to avoid overwatering, especially with our humid summers and frequent afternoon thunderstorms.

During the spring and fall, when rainfall is less frequent, check the soil moisture by sticking your finger about 2 inches deep. If it feels dry, water deeply, providing about an inch of water per week. In the heat of summer, with our regular rainfall and humidity, you may barely need to water at all.

It's best to water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our humid climate. Signs of underwatering include wilting leaves, while yellowing leaves can indicate overwatering. A light layer of pine straw mulch can help retain moisture without suffocating the roots, which is especially helpful with our clay soil.

You can expect your first harvest of nasturtium flowers and leaves around mid-June, about 55 days after planting. The harvest season extends well into late October, giving you plenty of time to enjoy these versatile plants.

Harvest flowers when they are fully open and at their peak color. For the leaves, snip them off with scissors or pinch them off with your fingers. Regular harvesting encourages more blooms and keeps the plants producing. As the first frost approaches in late October, harvest any remaining flowers and seed pods. The green seed pods can be pickled and used as a caper substitute.

Nasturtiums are generally easy to grow, but here are a few common problems you might encounter in the Southeast:

Aphids

• What it looks like: Clusters of tiny green, black, or brown insects on stems and undersides of leaves. Leaves may be distorted or sticky.
• What causes it: Aphids are attracted to stressed plants, and our hot, humid summers can sometimes weaken plants.
• How to fix/prevent it: Nasturtiums actually attract aphids *away* from other plants, acting as a trap crop. Monitor your plants regularly and hose off aphids with a strong stream of water. Introduce beneficial insects like ladybugs.

Cabbage Caterpillars

• What it looks like: Chewed leaves, often with large holes. You might see small green caterpillars on the plants.
• What causes it: These caterpillars are the larvae of cabbage white butterflies, which are common in the Southeast.
• How to fix/prevent it: Handpick caterpillars off the plants. Cover plants with row covers to prevent butterflies from laying eggs. Use Bacillus thuringiensis (Bt), a natural bacteria, to control caterpillars.

Black Fly

• What it looks like: Similar to aphids, but black. They suck sap and weaken the plants.
• What causes it: Warm weather and humidity can encourage black fly infestations.
• How to fix/prevent it: Spray with insecticidal soap. Encourage beneficial insects like lacewings. Make sure your plants have good air circulation to avoid creating humid microclimates.

Southeast Specific Challenges: The combination of heat and humidity in the Southeast can create an ideal environment for fungal diseases. Ensure good air circulation around your plants and avoid overhead watering to minimize disease pressure. Also, Japanese beetles can be a nuisance, so consider using traps or handpicking them off the plants.

Nasturtiums are great companions for many plants in your Southeast garden. They attract beneficial insects and can even repel some pests.

Tomatoes, cucumbers, and squash benefit from nasturtiums planted nearby because the flowers attract pollinators, increasing fruit production. Broccoli and cabbage also appreciate nasturtiums, as they can help deter cabbage white butterflies and other pests that target these brassicas. Avoid planting nasturtiums near fennel, as they can inhibit each other's growth.