Nasturtium in Zone 7A — Texas

Nasturtiums are a fantastic addition to any Texas garden. The peppery flavor of the leaves and flowers adds a unique zing to salads, and they're beautiful trailing out of containers or spilling over garden beds. Plus, they're easy to grow and attract beneficial insects, making them a winner in our unpredictable Texas climate.

We all know gardening in Texas can be a rollercoaster. The extreme heat, occasional droughts, and surprise freezes can be tough on plants. But with a little planning and the right timing, you can enjoy a bountiful harvest of nasturtiums during our long, 245-day growing season.

Starting nasturtiums indoors isn't usually necessary, since they do so well when direct sown. However, if you want a head start, or are trying to get a very early bloom before the Texas heat really kicks in, you can start seeds indoors from mid February through early March. This gives you about a 3-week window, roughly four weeks before you'd transplant them outside.

Use seed trays with a good seed-starting mix. Keep the soil consistently moist (bottom watering works great to prevent damping off) and provide warmth and light. Since spring comes early here, be prepared to harden them off and get them in the ground as soon as the weather allows.

Once the danger of frost has passed, usually from late March through mid April, you can transplant your nasturtiums outdoors. 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, spacing the plants 10-12 inches apart. Keep an eye on the weather forecast, as a late freeze can still happen. Be ready to cover your young plants if temperatures dip unexpectedly.

Direct sowing is the preferred method for nasturtiums, as they don't love having their roots disturbed. Wait until the soil has warmed up a bit, usually from late March through early September. This long window gives you plenty of flexibility.

Prepare the soil by loosening it and removing any large clumps. Sow seeds about ½ inch deep and 10-12 inches apart. Keep the soil consistently moist until the seedlings emerge, which usually takes about a week or two.

Nasturtiums are pretty low-maintenance when it comes to watering, which is good news for Texas gardeners dealing with our unpredictable rainfall and hot summers. They actually thrive in slightly poor, dry soil. Overwatering or over-fertilizing can lead to lots of foliage but fewer flowers.

During the spring and fall, when temperatures are milder, water only when the top 2 inches of soil feel dry to the touch – use the "finger test." In the heat of the summer, you might need to water once or twice a week, giving them about an inch of water each time if we haven't had rain. Water at the base of the plants to avoid fungal diseases, especially with our variable humidity.

If the leaves start to droop and turn yellow, you're likely overwatering. If the leaves are crispy and the plant looks wilted even in the morning, it's probably underwatered. A layer of mulch can help retain moisture in the soil and reduce the need for frequent watering, but be mindful of not keeping the soil too wet.

You can expect your first harvest of nasturtium flowers and leaves around mid May, about 55 days after sowing. The harvest can continue all the way through mid November if the weather cooperates.

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 flower production. Don't forget about the seed pods! They can be pickled and used as a caper substitute. As the first frost approaches in mid- November, harvest any remaining flowers and seed pods to preserve.

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

Aphids

• What it looks like: Tiny green, black, or white bugs clustered on stems and leaves. Leaves may be sticky or distorted.
• What causes it: Aphids are attracted to stressed plants, and our Texas heat can definitely stress them out. They also love lush, new growth.
• How to fix/prevent it: Nasturtiums are often used as a trap crop for aphids, drawing them away from other plants. You can spray them off with a strong stream of water, or introduce beneficial insects like ladybugs.

Cabbage Caterpillars

• What it looks like: Green caterpillars chewing holes in leaves. You might also see their droppings (frass) on the plants.
• What causes it: Cabbage white butterflies lay their eggs on nasturtiums, and the caterpillars hatch and start feeding. They are most prevalent during the warmer months.
• How to fix/prevent it: Handpick the caterpillars off the plants. You can also use row covers to prevent the butterflies from laying eggs in the first place.

Black Fly

• What it looks like: Clusters of small, black flies on new growth, particularly on the undersides of leaves. Leaves may become distorted or yellowed.
• What causes it: Black fly thrive in warm, humid conditions and can quickly multiply.
• How to fix/prevent it: Similar to aphids, a strong blast of water can dislodge them. Insecticidal soap can also be effective, but apply it in the evening to avoid harming beneficial insects.

Texas-Specific Challenges: The extreme heat and variable humidity in Texas can make nasturtiums more susceptible to pests and diseases. Providing adequate shade during the hottest part of the day, ensuring good air circulation, and avoiding overwatering can help keep your plants healthy. Also, watch out for fire ants when you're working in the garden!

Nasturtiums are great companion plants in the Texas garden. They attract pollinators and beneficial insects, and they can also help repel certain pests.

Good companions include:

• Tomatoes: Nasturtiums can help deter tomato hornworms and other pests.
• Cucumbers and Squash: They attract pollinators, which can improve fruit set.
• Broccoli and Cabbage: They can help deter cabbage moths and other cabbage family pests.

Avoid planting nasturtiums near fennel, as it can inhibit their growth.