Nasturtium in Zone 9A — Gulf Coast

Nasturtiums are a fantastic addition to any Gulf Coast garden. Their peppery leaves and bright, cheerful flowers add a unique flavor to salads and a pop of color to your plate. Plus, they're incredibly versatile – use the leaves, flowers, and even the seed pods! The satisfaction of growing something so useful and beautiful in our long growing season is hard to beat.

Our high humidity and disease pressure can be a challenge, but with proper timing and a little attention, nasturtiums thrive here. We have that long growing season, stretching nearly year-round, and nasturtiums are happy to take advantage of it.

Starting nasturtiums indoors is possible, but honestly, they prefer to be direct-sown. If you're eager to get a head start, begin in mid-January through early February, about four weeks before you plan to transplant. Use seed trays with good drainage and provide warmth and plenty of light.

Bottom watering is a great way to keep the soil consistently moist without overwatering from above. Our early spring often brings warm spells, so be ready to harden them off as soon as the weather allows.

Transplant your seedlings outdoors from mid-February through mid-March. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind. Space them about 10-12 inches apart.

Keep an eye on the weather – we sometimes get unexpected cool snaps this time of year, so be prepared to cover them if needed. Remember, nasturtiums don't love having their roots disturbed, so handle them gently.

Direct sowing is the way to go with nasturtiums! Sow seeds directly into your garden from mid-February through early October. Ensure the soil is well-draining and has warmed up a bit. Nasturtiums germinate best when the soil temperature is consistently around 65-70°F.

Plant the seeds about ½ inch deep and space them 10-12 inches apart. Water gently after sowing. Because we often get afternoon storms, good drainage is essential to prevent the seeds from rotting before they sprout.

Nasturtiums are surprisingly drought-tolerant and thrive on neglect, which is perfect for the Gulf Coast’s unpredictable weather. In our climate, less is definitely more when it comes to watering.

During the spring and fall, when rainfall is more consistent, you likely won't need to water them at all unless we experience a particularly dry spell. In the heat of summer, check the soil moisture with the "finger test" – stick your finger about 2 inches deep into the soil. If it feels dry, give them about ½ inch of water per week, focusing on watering at the base of the plant to avoid wetting the leaves and encouraging fungal diseases in our humid environment.

Overwatering can lead to lush foliage but fewer flowers, and it can also create conditions that favor fungal problems. Yellowing leaves are a sign of overwatering. Wilting leaves indicate underwatering. A light layer of pine straw mulch can help retain moisture and suppress weeds, but don't overdo it – nasturtiums prefer well-drained soil.

You can expect your first harvest of nasturtium flowers and leaves from mid-April through early December, about 55 days after planting. The flowers are ready to harvest when they are fully open and brightly colored. The leaves can be harvested at any time.

To harvest, simply snip the flowers or leaves with scissors or pinch them off with your fingers. Avoid pulling or tugging, which can damage the plant. Regular harvesting encourages continued production of both flowers and leaves.

As the first frost approaches in early December, harvest any remaining flowers and leaves. You can also collect the seed pods and pickle them for a caper-like treat.

Here are some common problems you might encounter with nasturtiums in the Gulf Coast:

Aphids

• What it looks like: Clusters of tiny green, black, or brown insects on stems and undersides of leaves; sticky "honeydew" on foliage; distorted or yellowing leaves.
• What causes it: Aphids are attracted to stressed plants, and our high humidity can sometimes weaken plants.
• How to fix/prevent it: Nasturtiums can be used as a trap crop to lure aphids away from other plants. If infestations are heavy, spray with a strong stream of water or insecticidal soap.

Cabbage Caterpillars

• What it looks like: Holes in leaves; green caterpillars feeding on foliage; dark droppings on plants.
• What causes it: Cabbage white butterflies lay their eggs on plants, and the caterpillars hatch and start eating.
• How to fix/prevent it: Handpick caterpillars off plants; cover plants with netting to prevent butterflies from laying eggs; use Bacillus thuringiensis (Bt) spray.

Black Fly

• What it looks like: Similar to aphids, but black in color and often found on new growth.
• What causes it: High humidity and warm temperatures create ideal conditions for black fly infestations.
• How to fix/prevent it: Spray with a strong stream of water or insecticidal soap. Ensure good air circulation around plants to discourage infestations.

Gulf Coast Specific Challenges: The combination of high heat, very-high humidity, and our wet-year-round rainfall creates an environment where fungal diseases can thrive. Ensure good air circulation, avoid overhead watering, and choose well-draining soil to minimize these issues.

Nasturtiums are great companion plants in the Gulf Coast garden. They attract beneficial insects and can even deter some pests.

Good companions include tomatoes, cucumbers, squash, broccoli, and cabbage. Nasturtiums deter aphids and cabbage white butterflies, protecting these crops. They also attract pollinators, which is crucial for fruit and vegetable production. Avoid planting nasturtiums near fennel, as they can inhibit each other's growth.