Nasturtium in Zone 8A — Gulf Coast

Nasturtiums are worth growing here on the Gulf Coast because they're so versatile. The peppery taste of the leaves and flowers adds a zing to salads, and you can even pickle the seed pods. Plus, they're just plain cheerful to look at, and easy to grow in our long growing season.

Even with our high humidity and occasional hurricane scares, nasturtiums are a fairly low-fuss crop if you time things right. We have a long 269-day growing season, so you have plenty of opportunity to get a few harvests in.

Starting nasturtiums indoors isn't usually necessary here; they actually do better when direct sown. However, if you're wanting an extra-early start, you can start them indoors from early to late February, about four weeks before our typical last frost.

Use seed trays with good drainage and a light potting mix. Keep them warm and provide plenty of light – a sunny windowsill or grow lights work well. Bottom watering helps prevent damping off. Remember, though, our spring weather can be unpredictable, so be prepared to protect those seedlings from a late cold snap.

Transplant your nasturtium seedlings outdoors from early March through early April. Before you put them in the ground, harden them off for about a week. Give them increasing amounts of time outdoors to adjust to the sunlight and temperatures.

Space them about 10-12 inches apart. Keep an eye on the weather forecast – those early spring days can still bring a surprise frost. You want to wait until the soil has warmed up a bit.

Direct sowing is really the way to go with nasturtiums on the Gulf Coast. You can start sowing seeds directly into the garden from early March through mid September. This gives you a long window to get several plantings in.

Choose a spot with full sun to partial shade, and make sure the soil is well-draining. Nasturtiums aren't picky about soil, but they do need it to be warm enough for germination. Sow seeds about half an inch deep and 10-12 inches apart. Keep the soil consistently moist until they sprout, usually in about a week or two.

Nasturtiums are pretty drought-tolerant, which is great for our often-wet climate. They actually thrive in slightly poor, dry soil, so don't overdo it with the watering or fertilizer. Too much of either will give you lots of leaves but fewer flowers.

During the hotter months, especially July and August, give them about an inch of water per week if we're not getting regular rainfall. Use the finger test: stick your finger about two inches into the soil, and if it feels dry, it's time to water. Water at the base of the plant to avoid getting the leaves wet, since our high humidity can lead to fungal problems. 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 in our heavy Gulf Coast soils.

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

To harvest, simply snip the flowers or leaves off with scissors or your fingers. Regular harvesting encourages more blooms and keeps the plant producing. As we approach late November and the chance of frost increases, harvest any remaining flowers and leaves. You can even try pickling any remaining seed pods for a caper-like treat to extend the season.

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

Aphids

• What it looks like: Clusters of small, pear-shaped insects on stems and undersides of leaves. Leaves may be sticky or distorted.
• What causes it: Aphids are attracted to stressed plants, and our humid conditions can sometimes weaken plants.
• How to fix/prevent it: Nasturtiums can actually be used as a trap crop for aphids, drawing them away from other plants. If infestations get too heavy, spray with a strong jet of water or use insecticidal soap.

Cabbage Caterpillars

• What it looks like: Holes in leaves, often with green or brown droppings nearby. You might see small green caterpillars.
• What causes it: Cabbage white butterflies lay their eggs on nasturtiums, and the caterpillars hatch and start munching.
• How to fix/prevent it: Handpick caterpillars when you see them. You can also cover plants with floating row covers to prevent butterflies from laying eggs.

Black Fly

• What it looks like: Similar to aphids, black fly are small black insects that cluster on new growth and suck plant juices. Leaves may curl or become distorted.
• What causes it: Like aphids, black fly thrive in warm, humid conditions and can quickly multiply.
• How to fix/prevent it: A strong blast of water from the hose can dislodge them. Insecticidal soap can also be effective.

Gulf Coast Specific Challenges: Our hot heat, very-high humidity, and wet-year-round rainfall can create ideal conditions for pests and diseases. Be vigilant about monitoring your plants, and take action quickly when you spot a problem. Good air circulation and well-draining soil are key to keeping your nasturtiums healthy in our challenging climate.

Nasturtiums are great companion plants for several vegetables here on the Gulf Coast. Plant them near tomatoes to help deter tomato hornworms. They also do well near cucumbers and squash, attracting pollinators and helping to keep squash bugs away. Broccoli and cabbage benefit from nasturtiums as well, since they can help repel cabbage moths and other pests. Avoid planting nasturtiums near fennel, as they can inhibit each other's growth.