Nasturtium in Zone 5B — Great Plains

Nasturtiums are a fantastic addition to any Great Plains garden. Their peppery leaves and vibrant flowers add a unique zest to salads and make beautiful garnishes. Plus, they’re incredibly easy to grow, offering a big reward for minimal effort. In our region, where extreme weather can be a challenge, having a resilient and versatile plant like nasturtium is a real win.

While the Great Plains can throw some curveballs with its temperature swings and variable rainfall, nasturtiums are surprisingly adaptable. With a 178-day growing season, you have plenty of time to enjoy these beauties, even if spring gets off to a slow start. The key is understanding their needs and working with our climate.

Starting nasturtiums indoors is possible, but honestly, it's usually not necessary here in the Plains. They resent transplanting, so direct sowing is generally the way to go. However, if you’re itching to get a head start, or if you're in the northern part of our region with a slightly shorter growing season, you can start seeds indoors late March through mid April, about four weeks before the last expected frost.

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. Be sure to water from the bottom to avoid damping off. Keep in mind that our springs can be unpredictable, with temperature swings that can stress young seedlings, so watch the weather closely before transplanting.

If you started your nasturtiums indoors, transplant them outdoors late April through late May, after the danger of frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Plains's often-windy conditions and intense sunshine.

Space the plants 10-12 inches apart. Remember, the Plains can still have some cool snaps during this time, so keep an eye on the forecast and be ready to cover them if a late frost threatens.

Direct sowing is the preferred method for nasturtiums in the Great Plains, as they don't love having their roots disturbed. Sow seeds late April through early August, once the soil has warmed up a bit. Choose a spot with full sun to part shade.

Prepare the soil by loosening it and removing any large clumps. Nasturtiums aren't picky about soil, but good drainage is essential. Plant the seeds about ½ inch deep, spacing them 10-12 inches apart. Keep the soil consistently moist until the seedlings emerge, which should take about a week or two.

Nasturtiums are drought-tolerant and actually thrive on neglect, which is perfect for our variable Plains climate. Overwatering is a far bigger concern than underwatering with these plants. During the hot summer months, especially if rainfall is scarce, check the soil moisture regularly using the "finger test" – stick your finger about 2 inches deep into the soil.

If it feels dry, give them a good soaking, aiming for about ½ inch of water per week, depending on rainfall. Water at the base of the plants to avoid wetting the foliage, as our low-to-moderate humidity can still lead to fungal issues if the leaves stay wet for too long. Yellowing leaves can be a sign of overwatering, while wilting indicates they need a drink. A light layer of mulch can help retain moisture and keep the soil cool during the hottest part of the summer.

You can expect your first nasturtium harvest in late June through mid October, about 55 days after planting. Both the flowers and leaves are edible and add a peppery kick to salads and other dishes. The flowers are at their best when fully open, displaying their vibrant colors.

Harvest the leaves and flowers as needed, snipping them off with scissors or your fingers. Regular harvesting encourages more blooms. Even the seed pods can be harvested and pickled for a caper-like treat. As the first frost approaches in mid- October, harvest any remaining flowers and leaves to preserve their flavor, or let the seed pods dry on the plant to collect seeds for next year.

Nasturtiums are generally low-maintenance, but here are a few common problems you might encounter in the Great Plains:

Aphids *What it looks like:* Clusters of tiny green or black bugs on stems and leaves, often causing distorted or sticky foliage. *What causes it:* Aphids are attracted to stressed plants and can thrive in warm, dry conditions, which we often experience in the Plains. *How to fix/prevent it:* Nasturtiums can actually serve as a trap crop for aphids, drawing them away from other plants. If infestations get heavy, spray with a strong jet of water or use insecticidal soap.

Cabbage Caterpillars *What it looks like:* Holes in leaves, often with green caterpillars present. *What causes it:* Cabbage white butterflies lay their eggs on the underside of leaves, and the caterpillars hatch and start munching. *How to fix/prevent it:* Handpick caterpillars when you see them, or use Bacillus thuringiensis (Bt), a natural bacteria that targets caterpillars.

Black Fly *What it looks like:* Tiny black flies swarming around the plant, often on new growth. Leaves may be sticky or distorted. *What causes it:* Black flies are attracted to moist conditions and can quickly multiply in warm weather. *How to fix/prevent it:* Improve air circulation around the plants and avoid overwatering. Insecticidal soap can also help control infestations.

Great Plains Specific Challenges: The hot heat of our summers can stress nasturtiums, making them more susceptible to pests. Consistent watering during dry spells is crucial, but avoid overwatering, which can lead to fungal diseases. The variable rainfall and temperature swings of the Plains can also impact growth, so monitor your plants closely and adjust your care as needed.

Nasturtiums make excellent companion plants in the Great Plains garden. They deter pests and attract beneficial insects, which can help protect your other crops.

Good companions:

• Tomato: Nasturtiums repel tomato hornworms and whiteflies.
• Cucumber: They deter cucumber beetles.
• Squash: They help control squash bugs.
• Broccoli and Cabbage: They can distract cabbage moths, protecting these brassicas from cabbage worms.

Avoid planting nasturtiums near fennel or other members of the brassica family that attract aphids.