Nasturtium in Zone 9A — Texas

Nasturtiums are a fantastic addition to any Texas garden. Their peppery leaves and bright flowers add zest to salads and sandwiches, plus they're super easy to grow. In our climate, you can enjoy a long harvest window, adding beauty and flavor to your meals for months.

While Texas weather can be unpredictable, with our long growing season (around 293 days), you've got plenty of time to get nasturtiums established. Just keep an eye on the forecast and adjust your plans accordingly, especially with our occasional late freezes.

Starting nasturtiums indoors isn't usually necessary here in Texas, but it can give you a head start if you're eager for early blooms. If you want to go this route, start your seeds indoors from mid January through early February, about four weeks before you plan to transplant them outside.

Use seed trays with a good seed-starting mix, and keep them in a warm spot with plenty of light – a sunny windowsill or under grow lights works well. Water from the bottom to prevent damping off; just set the tray in a shallow dish of water until the soil surface is moist. With our early springs, getting a jump start indoors can mean even earlier blooms.

Transplant your nasturtium seedlings outdoors from late February through late March, once the danger of frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week.

Choose a spot with full sun to partial shade, and space the plants about 10-12 inches apart. Keep an eye on the weather forecast – those late cold snaps can still happen. If a freeze is predicted, cover your seedlings with frost cloth to protect them.

Direct sowing is the easiest and most recommended method for growing nasturtiums in Texas. You can direct sow from late February through late September, giving you plenty of flexibility.

Choose a spot with well-draining soil, and make sure the soil temperature is at least 65°F. Sow the seeds about ½ inch deep, spacing them 10-12 inches apart. Nasturtiums don’t love having their roots disturbed, so direct sowing avoids any transplant shock.

Nasturtiums are pretty drought-tolerant, which is a huge plus for Texas gardeners dealing with our unpredictable rainfall and summer heat. They actually thrive in slightly poor, dry soil, so don't overdo it with the water or fertilizer. You'll end up with lots of leaves and fewer flowers.

During the spring and fall, when temperatures are milder, water only when the top two inches of soil feel dry to the touch – use the "finger test." Aim for about ½ inch of water per week, depending on rainfall. During the brutal Texas heat of summer, you might need to water a bit more frequently, but still be cautious.

Water at the base of the plants to avoid getting the leaves wet, especially with our variable humidity. Overwatering can lead to root rot, while underwatering will cause the leaves to wilt. A layer of mulch can help retain moisture and keep the soil cool during the hottest months.

You can expect your first harvest of nasturtium flowers and leaves starting in mid April and continuing through early December. Nasturtiums are ready to harvest about 55 days after planting.

Harvest the flowers when they are fully open and the leaves when they are young and tender. Simply snip them off with scissors or pinch them off with your fingers. Regular harvesting encourages more blooms and keeps the plant producing.

As the first frost approaches in early December, harvest any remaining flowers and seed pods. The seed pods can be pickled and used like capers, adding a unique flavor to your winter dishes.

Here are some common problems you might encounter with nasturtiums in Texas:

Aphids

• What it looks like: Clusters of tiny green, black, or brown bugs on the stems and undersides of leaves. Leaves may be sticky or distorted.
• What causes it: Aphids thrive in warm, dry conditions, which we often have in Texas. They're attracted to stressed plants.
• How to fix/prevent it: Nasturtiums are great as a trap crop! They attract aphids away from other plants. You can also spray them off with a strong stream of water or use insecticidal soap.

Cabbage Caterpillars

• What it looks like: Green caterpillars feeding on leaves, leaving behind holes. You might also see their droppings (frass) on the plants.
• What causes it: These caterpillars are the larvae of cabbage white butterflies, which are common in Texas gardens.
• How to fix/prevent it: Handpick the caterpillars off the plants or use Bacillus thuringiensis (Bt), a biological insecticide. Row covers can also help prevent the butterflies from laying eggs on your nasturtiums.

Black Fly

• What it looks like: Tiny black flies swarming around the plants, especially in the early morning or late evening.
• What causes it: Black flies are attracted to moist soil and decaying organic matter, which can be a problem after our unpredictable rainfall.
• How to fix/prevent it: Improve drainage to prevent waterlogged soil. Use yellow sticky traps to catch the flies. Avoid overwatering.

Texas Specific Challenges: The extreme heat and variable humidity in Texas can stress nasturtiums, making them more susceptible to pests and diseases. Make sure to provide adequate shade during the hottest part of the day and water consistently, but not excessively. Keep an eye out for pests and diseases, and take action promptly to prevent them from spreading.

Nasturtiums are great companion plants for many vegetables in the Texas garden. They attract beneficial insects and can even act as a trap crop for aphids.

• Tomato: Nasturtiums deter pests like whiteflies and tomato hornworms.
• Cucumber: They help repel cucumber beetles.
• Squash: They attract pollinators, improving squash yields.
• Broccoli & Cabbage: They can help deter cabbage moths and other pests that attack these crops.

Avoid planting nasturtiums near fennel, as they can inhibit each other's growth.