Nasturtium in Zone 8B — Texas

Nasturtiums are a fantastic addition to any Texas garden. Their peppery leaves and vibrant flowers add a unique flavor to salads, plus they attract beneficial insects while deterring some pests. And let's be honest, in the Texas heat, a plant that thrives with minimal watering is a winner.

Our unpredictable weather can be a challenge, with everything from late freezes to intense heat waves. But with our long growing season, typically around 273 days, you have plenty of time to get your nasturtiums established and enjoy their beauty and flavor.

Starting nasturtiums indoors is possible, but generally not necessary here in Texas. Because our spring starts early, you're better off direct-sowing after the last threat of frost. However, if you want a head start, you can start seeds indoors from late January through mid February, about four weeks before you plan to transplant.

Use seed trays or small pots filled with a well-draining potting mix. Keep the soil consistently moist by bottom watering. Place the trays in a warm location with plenty of light, either from a sunny window or a grow light.

Transplant your nasturtium seedlings outdoors from early March through early April, after the danger of frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Choose a location with full sun to part shade and space the plants 10-12 inches apart. Keep an eye on the weather forecast – a sudden cold snap can still happen, so be ready to cover your seedlings if needed.

Direct sowing is the preferred method for nasturtiums, as they don't always love being transplanted. Wait until early March through mid September to sow your seeds directly into the garden.

Prepare the soil by loosening it and removing any weeds. Nasturtiums aren't picky and will thrive in poor soil, so don't worry about adding too much fertilizer. Sow the seeds about ½ inch deep and 10-12 inches apart. Keep the soil consistently moist until the seedlings emerge, which should take about a week.

Nasturtiums are drought-tolerant and actually prefer drier conditions, making them perfect for Texas gardens. Overwatering and over-fertilizing lead to more foliage than flowers, so less is more.

During the spring and fall, when temperatures are milder, water only when the soil feels dry about two inches below the surface. You can use the "finger test" for this. In the peak of summer's hot-to-extreme heat, you might need to water once a week, giving them about an inch of water. Water at the base of the plants to avoid fungal diseases, especially with our variable humidity.

Yellowing leaves can indicate overwatering, while wilting leaves signal underwatering. A light layer of mulch can help retain moisture in the soil during the hottest months, but don't overdo it, as nasturtiums like well-drained soil.

You can expect your first harvest of nasturtium flowers and leaves in late April, about 55 days after sowing. The harvest window extends through late November, or until the first frost.

Harvest flowers when they are fully open and leaves when they are young and tender. Snip them off with scissors or your fingers, being careful not to damage the plant. Regular harvesting encourages continued production. As the first frost approaches in late November, harvest any remaining flowers and leaves. You can even pickle the green seed pods for a caper-like treat!

Here are the top 3 problems you might encounter growing nasturtiums in Texas:

Aphids

• What it looks like: Tiny green, black, or brown insects clustered on stems and leaves. Leaves may be sticky or distorted.
• What causes it: Aphids are attracted to stressed plants, and our unpredictable swings in temperature and rainfall can sometimes weaken them.
• How to fix/prevent it: Nasturtiums actually attract aphids away from other plants, acting as a trap crop. If the infestation is heavy, you can spray the plants with a strong stream of water or use insecticidal soap.

Cabbage Caterpillars

• What it looks like: Green caterpillars munching on leaves, leaving holes. You might also see small white butterflies fluttering around.
• 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 natural insecticide.

Black Fly

• What it looks like: Small, black, fly-like insects clustered on new growth. Leaves may be stunted or distorted.
• What causes it: Black fly thrive in warm, humid conditions, which we definitely get in Texas.
• How to fix/prevent it: Similar to aphids, a strong spray of water can dislodge them. You can also use insecticidal soap.

Texas Specific Challenges: The extreme heat, variable humidity, and unpredictable rainfall in Texas can stress nasturtiums, making them more susceptible to pests and diseases. Consistent monitoring and appropriate watering are key to keeping your plants healthy.

Nasturtiums are great companions for many plants in the Texas garden! They attract beneficial insects and can even deter some pests.

• Tomato: Nasturtiums help repel tomato hornworms and whiteflies.
• Cucumber & Squash: They deter squash bugs and cucumber beetles, which can be a real problem here.
• Broccoli & Cabbage: Nasturtiums help deter cabbage moths, whose caterpillars can decimate these crops.

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