Nasturtium in Zone 6B — Southeast

Nasturtiums are a fantastic addition to any Zone 6B Southeast garden. Not only are the leaves and flowers peppery and delicious in salads, but they also attract beneficial insects. Plus, the vibrant colors are a welcome sight in our long summer!

While we do have our share of challenges here in the Southeast – humidity, Japanese beetles, and clay soil, to name a few – nasturtiums are surprisingly easy to grow with the right timing. Our long 208-day growing season gives you plenty of opportunity to enjoy these beauties.

Starting nasturtiums indoors is possible, but honestly, they do best when direct-sown. However, if you want a head start, especially for an earlier bloom, you can start seeds indoors from early to late March.

Use seed trays with a good seed-starting mix, keep them warm, and provide plenty of light. Bottom watering is a great way to keep the soil moist without overwatering. Given our moderate springs here in the Southeast, you'll want to keep an eye on soil moisture levels as things warm up.

If you started your nasturtiums indoors, transplant them outdoors from mid April through early May, after the last frost. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week.

Space them about 10-12 inches apart. Keep an eye on the weather forecast; those late-season cold snaps can still happen here in the Southeast, so be ready to cover them if needed!

Direct sowing is the way to go with nasturtiums! Wait until mid April through late August, once the soil has warmed up. They don't like the cold.

Prepare your soil by loosening it and removing any large clumps. Plant the seeds about half an inch deep, spacing them 10-12 inches apart. Nasturtiums really do resent having their roots disturbed, so direct sowing gives them the best start.

Nasturtiums are pretty low-maintenance when it comes to watering, which is great for our hot and humid Southeast summers. They actually thrive in slightly poor, dry soil, and overwatering can lead to more leaves than flowers. Less is definitely more with these plants.

During our wet-summer months, from June to August, you might not need to water them at all unless we're having a particularly dry spell. Use the finger test: stick your finger about 2 inches into the soil. If it's dry, give them a good watering, about an inch of water per week. With our humidity, it's best to water at the base of the plant to avoid fungal issues.

If the leaves are wilting or turning yellow, you're likely overwatering. If they're crisp and brown, they need more water. A light layer of pine straw mulch can help retain moisture without creating too much dampness, which is a plus in our humid climate.

You can expect your first nasturtium harvest from early June through late October, about 55 days after planting. Both the flowers and leaves are edible, so keep an eye out for fully opened blooms. The seed pods can also be harvested and pickled, like capers.

To harvest, simply snip off the flowers or leaves with scissors, being careful not to damage the rest of the plant. Regular harvesting encourages more blooms and keeps the plant producing throughout our long growing season. As late October approaches and the first frost threatens, harvest any remaining flowers and seed pods to enjoy before the cold arrives.

Here are a few common problems you might encounter with nasturtiums in Zone 6B, Southeast:

Aphids

• What it looks like: Tiny green, black, or brown bugs clustered on stems and leaves, often causing distorted growth.
• What causes it: Aphids are attracted to stressed plants. In the Southeast, they thrive in the warm, humid conditions.
• How to fix/prevent it: Nasturtiums are often used as a trap crop for aphids, drawing them away from other plants. Blast them off with a strong stream of water from your hose. Insecticidal soap can also be effective.

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 the underside of leaves. These caterpillars can be particularly bad in the Southeast due to our long growing season.
• How to fix/prevent it: Handpick the caterpillars off the plants. You can also use Bacillus thuringiensis (Bt), a biological insecticide. Row covers can prevent the butterflies from laying eggs.

Black Fly

• What it looks like: Small black flies around the base of the plant. Leaves may yellow or wilt.
• What causes it: Poor drainage and overly wet soil, common problems with our clay soil in the Southeast, can create a breeding ground for black flies.
• How to fix/prevent it: Improve drainage by amending your soil with compost and other organic matter. Avoid overwatering. Yellow sticky traps can help control the adult flies.

Southeast Specific Challenges: The hot heat and humid humidity of the Southeast can create favorable conditions for fungal diseases on nasturtiums. Good air circulation and avoiding overhead watering can help prevent these issues. Japanese beetles can also be a nuisance, so keep an eye out for them and handpick them off the plants as needed.

Nasturtiums make great companions for several plants in the Southeast garden. They attract pollinators and beneficial insects, while also acting as a trap crop for aphids.

Good companions include tomatoes, cucumbers, and squash because the nasturtiums can help deter pests that commonly attack these crops. Broccoli and cabbage also benefit from nasturtiums, as they can help repel cabbage moths. Avoid planting them near fennel, as it can inhibit their growth.