Nasturtium in Zone 8A — Southeast

Nasturtiums are a fantastic addition to any Southeast garden. The peppery leaves and bright flowers add a unique flavor to salads, and they're incredibly versatile in the kitchen. Plus, their cheerful blooms bring a splash of color to our gardens during our long summer.

While we definitely have our share of gardening challenges here in the Southeast – think humidity, fungal diseases, and the occasional unwelcome visit from Japanese beetles – nasturtiums are surprisingly resilient. With a little attention to timing, you can enjoy a long season of beautiful blooms and delicious leaves, thanks to our 245-day growing season.

Starting nasturtiums indoors isn't essential, since they actually prefer to be direct-sown, but it can give you a head start. If you're eager to see those first blooms, start seeds indoors from mid February through early March, about four weeks before you plan to transplant.

Use seed trays filled with a well-draining potting mix. Keep them warm and provide plenty of light – a sunny windowsill or grow lights work well. Bottom watering helps prevent damping off, which can be a problem with our moderate Southeast springs.

Transplant your nasturtium seedlings outdoors from late March through mid April, once the danger 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 to allow for their trailing growth habit. Keep an eye on the weather forecast – those late-season temperature swings can still happen, so be ready to cover your young plants if needed.

Direct sowing is the preferred method for nasturtiums, as they don't always love having their roots disturbed. Wait until late March through early September to sow your seeds directly into the garden.

Choose a spot with full sun to part shade and prepare the soil by loosening it and removing any weeds. Nasturtiums aren't picky about soil – in fact, they thrive in slightly poor soil. Sow seeds about ½ inch deep and space them 10-12 inches apart.

Nasturtiums are wonderfully low-maintenance when it comes to watering, which is great for our busy summers. They actually prefer drier conditions, and too much water can lead to more foliage than flowers.

During our wet-summer months, you might not need to water them at all, unless we're experiencing a particularly dry spell. Otherwise, aim to water deeply but infrequently – about once a week, or when the top two inches of soil feel dry to the touch (the "finger test"). An inch of water per week is usually sufficient. Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our humid climate.

If the leaves start to wilt or turn yellow, you're likely overwatering. If they're dry and crispy, you need to water more. A light layer of pine straw mulch can help retain moisture without making the soil too soggy, and also help keep weeds down.

You can expect your first harvest of nasturtium flowers and leaves from mid May through mid November, about 55 days after sowing. The flowers are ready to harvest when they're fully open and brightly colored.

Snip the flowers or leaves off with scissors or your fingers, being careful not to damage the plant. Regular harvesting encourages more blooms, so don't be shy! As the first frost approaches in mid- November, harvest any remaining flowers and seed pods – the seed pods can be pickled for a unique, caper-like treat.

Here are a few common problems you might encounter with nasturtiums in the Southeast:

Aphids

• What it looks like: Clusters of tiny, soft-bodied insects on stems and leaves, often accompanied by sticky honeydew.
• What causes it: Aphids are attracted to stressed plants, and our humid summers can sometimes create conditions that favor their development.
• How to fix/prevent it: Nasturtiums can actually be used as a trap crop to lure aphids away from other 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 the leaves, often with green droppings nearby. You might also spot small green caterpillars munching away.
• What causes it: These caterpillars are the larvae of cabbage white butterflies, which are common in our region.
• How to fix/prevent it: Handpick the caterpillars off the plants or use Bacillus thuringiensis (Bt), a natural insecticide.

Black Fly

• What it looks like: Similar to aphids, you'll see clusters of small, black flies on the plant, usually around new growth.
• What causes it: Like aphids, they thrive in humid conditions and target weak plants.
• How to fix/prevent it: Regular monitoring and strong blasts of water can help keep them at bay. Insecticidal soap can be effective for heavier infestations.

Southeast Specific Challenges: Our hot heat and humid humidity can create ideal conditions for fungal diseases on nasturtiums. Ensure good air circulation by spacing plants appropriately, and avoid overhead watering, especially in the evenings.

Nasturtiums are great companions for many plants in the Southeast garden. They attract beneficial insects and can even act as a trap crop for aphids, protecting your other veggies.

Good companions include tomatoes, cucumbers, and squash – nasturtiums can help deter pests that commonly attack these plants. They're also beneficial near broccoli and cabbage, as they can help repel cabbage white butterflies. Avoid planting nasturtiums near fennel, as they can inhibit each other's growth.