Nasturtium in Zone 6A — Great Plains

Nasturtiums are worth growing in the Great Plains for their peppery flavor, versatility in the kitchen, and cheerful blooms that attract pollinators. Every part of the plant is edible, adding a unique zest to salads, sandwiches, and even desserts. Plus, they thrive in our prairie soil and tolerate the intense sunshine that can be a challenge for other plants.

Our region's extreme weather, from spring temperature swings to summer heat and potential hail, can be daunting. But with a well-timed planting schedule within our 188-day growing season, you can enjoy a bountiful harvest of Nasturtiums from mid-June through mid-October.

Starting Nasturtiums indoors is possible but not always necessary. These plants resent transplanting, so direct sowing is generally preferred. However, if you're eager to get a head start, especially in the northern Plains where the growing season is shorter, starting seeds indoors can be beneficial.

If you choose to start indoors, sow seeds mid-March through early April, about 4 weeks before you plan to transplant them. Use seed trays with well-draining potting mix, provide warmth, and ensure they receive plenty of light. Bottom watering is a great way to keep the soil moist without overwatering. Be mindful of our region's variable spring weather; an unexpected cold snap could delay your transplanting plans.

Transplant your Nasturtium seedlings outdoors late April through mid May, after the last expected frost. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the intense Plains sunshine and wind.

Space the plants 10-12 inches apart to allow for their trailing growth habit. Keep an eye on the weather forecast; a late-season frost or hailstorm could damage young transplants, so be prepared to cover them if necessary.

Direct sowing is the recommended method for growing Nasturtiums in the Great Plains. Since they don't love being transplanted, sowing directly into the garden avoids unnecessary stress on the plants. Sow seeds late April through mid August, after the danger of frost has passed.

Choose a sunny spot with well-draining soil. While Nasturtiums aren't picky about soil, they do need warmth to germinate. Simply press the seeds into the soil about half an inch deep and water gently. Space the seeds 10-12 inches apart. With consistent moisture and warm temperatures, you should see seedlings emerge within a week or two.

Nasturtiums are surprisingly drought-tolerant and thrive in the dry conditions we often experience in the Great Plains. In fact, too much water can lead to lush foliage at the expense of flowers, so less is definitely more.

During the spring, when rainfall is more frequent, you may not need to water your Nasturtiums at all. Once the summer heat arrives, check the soil moisture regularly. Stick your finger about 2 inches deep into the soil; if it feels dry, it's time to water. Aim for about 1 inch of water per week, either from rainfall or irrigation.

Water at the base of the plants to avoid wetting the leaves, which can increase the risk of fungal diseases in our low-to-moderate humidity. Signs of underwatering include wilting leaves and stunted growth, while overwatering can cause yellowing leaves and root rot. Mulching around the plants with straw or wood chips can help retain moisture and regulate soil temperature during our extreme temperature swings.

You can expect your first Nasturtium harvest from mid-June through mid-October, about 55 days after planting. The flowers, leaves, and seed pods are all edible, offering a peppery kick to your culinary creations. Harvest flowers when they are fully open for the best flavor and visual appeal.

To harvest, simply snip off the flowers or leaves with scissors or your fingers. Be gentle to avoid damaging the plant, and try to harvest regularly to encourage continued production. As the first frost approaches in mid-October, harvest any remaining flowers and seed pods to preserve their flavor and use them in pickles or other recipes.

Here are three common problems you might encounter growing Nasturtiums in the Great Plains:

Aphids

• What it looks like: Clusters of small, pear-shaped insects on stems and leaves, often accompanied by sticky honeydew and sooty mold.
• What causes it: Aphids are attracted to stressed plants. Our region's temperature swings and occasional drought can weaken plants, making them more susceptible.
• How to fix/prevent it: Nasturtiums can actually be used as a trap crop to lure aphids away from other plants. If the infestation is heavy, spray with insecticidal soap or blast them off with a strong stream of water.

Cabbage Caterpillars

• What it looks like: Holes in leaves, often with green or brown caterpillars present.
• What causes it: Cabbage white butterflies lay eggs on Nasturtium leaves, which hatch into hungry caterpillars.
• How to fix/prevent it: Handpick the caterpillars off the plants or cover them with netting to prevent butterflies from laying eggs. Bacillus thuringiensis (Bt) is an effective organic control option.

Black Fly

• What it looks like: Small, black flies swarming around the plants, often accompanied by yellowing leaves.
• What causes it: Black flies thrive in moist conditions and are attracted to decaying organic matter.
• How to fix/prevent it: Improve drainage around the plants and remove any fallen leaves or debris. Insecticidal soap can help control infestations.

Great Plains Specific Challenges: The hot heat and variable rainfall of the Great Plains can stress Nasturtiums, making them more susceptible to pests and diseases. Consistent monitoring and proper watering are key to keeping your plants healthy and productive.

Nasturtiums are great companions for many garden plants in the Great Plains, and help some of our most-grown backyard favorites. They act as a trap crop for aphids, drawing them away from your tomatoes, cucumbers, and squash. They also deter cabbage white butterflies, protecting your broccoli and cabbage from cabbage caterpillars. The flowers attract pollinators, which benefit all your fruiting vegetables.

Avoid planting Nasturtiums near fennel or other members of the brassica family (like kale or Brussels sprouts) as they can attract the same pests. Otherwise, Nasturtiums are generally easygoing companions that can enhance your Great Plains garden.