Nasturtium in Zone 3A — Great Plains

Nasturtiums are a fantastic addition to any Great Plains garden. Their peppery leaves and bright flowers add a unique flavor to salads, and they're versatile enough to use in everything from pesto to stir-fries. Plus, the sheer joy of watching these cheerful plants thrive, even with our variable weather, is incredibly rewarding.

Our short, 108-day growing season and tendency for extreme weather can be daunting, but nasturtiums are surprisingly resilient. By understanding the best timing for planting and watering, you can easily enjoy a bountiful harvest of these flavorful flowers and leaves.

Starting nasturtiums indoors is possible, but honestly, it's usually not necessary here in the Great Plains. Nasturtiums resent transplanting, so direct sowing is generally the preferred method. However, if you're itching to get a head start, especially in the northern part of our region with its shorter season, you can start seeds indoors from late April through mid May, about four weeks before transplanting.

Use seed trays with good drainage and provide warmth and plenty of light. Bottom watering is key to prevent damping off; just set the tray in a shallow dish of water until the soil surface is moist. Keep in mind that spring weather can be unpredictable, so be prepared to adjust your plans if we have a late cold snap.

If you started your nasturtiums indoors, aim to transplant them outdoors from early to late June, once the risk of frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the stronger sunlight and temperature fluctuations they'll experience in the garden.

Space your plants 10-12 inches apart to allow for their trailing growth habit. Keep an eye on the weather forecast; a late hailstorm or a sudden temperature drop can set back young transplants. Wind protection is also essential, especially in exposed areas of the Plains.

Direct sowing is the easiest and most successful way to grow nasturtiums in the Great Plains. Wait until the soil has warmed up and the danger of frost is gone, typically from early June through early July. Choose a sunny spot with well-drained soil.

Prepare the soil by loosening it and removing any weeds or rocks. Sow seeds 1/2 inch deep and 10-12 inches apart. Keep the soil consistently moist until the seedlings emerge, usually within a week or two. Remember, nasturtiums actually prefer slightly poor soil, so don't over-amend it with compost or fertilizer.

Nasturtiums are surprisingly drought-tolerant and thrive in less-than-ideal soil conditions, which makes them perfect for the Great Plains. In fact, overwatering or over-fertilizing can actually lead to more foliage and fewer flowers. Less is definitely more when it comes to watering these plants.

During our hot summer months (typical highs around 93°F), aim to water deeply but infrequently. A good rule of thumb is to check the soil moisture about two inches below the surface – if it feels dry, it's time to water. Typically, an inch of water per week is sufficient, but adjust based on rainfall and temperature.

Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases, especially during periods of higher humidity. Signs of underwatering include wilting leaves and stunted growth, while overwatering can lead to yellowing leaves and root rot. A light layer of mulch can help retain moisture and suppress weeds, but be careful not to overdo it in our sometimes humid climate.

Your first nasturtium harvest should be in late July through early September, about 55 days after planting. The flowers, leaves, and even the seed pods are all edible, so there's plenty to enjoy! Harvest flowers when they are fully open and at their peak color.

To harvest, simply snip the flowers or leaves from the plant with scissors or your fingers. Avoid pulling or tugging, as this can damage the plant. Regular harvesting encourages continued production, so don't be shy about picking those flowers and leaves!

As our first frost approaches in early September, harvest any remaining flowers and seed pods. You can pickle the seed pods for a caper-like treat or let some of the flowers go to seed to collect for next year's planting.

Here are some common issues to watch out for with Nasturtiums in the Great Plains:

Aphids (intentional trap crop)

• 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 lush, tender growth, which can be exacerbated by over-fertilizing or overwatering. In our region, extreme temperature swings can also stress plants, making them more susceptible.
• How to fix/prevent it: Nasturtiums are often used as trap crops for aphids, drawing them away from other plants. You can spray aphids off with a strong stream of water or use insecticidal soap if the infestation is severe.

Cabbage Caterpillars

• What it looks like: Holes in leaves, often with green or brown caterpillars present.
• What causes it: Cabbage white butterflies lay their eggs on the underside of leaves, and the caterpillars hatch and feed on the foliage.
• How to fix/prevent it: Handpick caterpillars off the plants, especially in the early morning or evening. You can also use row covers to prevent butterflies from laying eggs on the plants. Bacillus thuringiensis (Bt) is an effective organic insecticide for controlling caterpillars.

Black Fly

• What it looks like: Tiny black flies swarming around the plants, especially in warm, humid conditions.
• What causes it: Black flies are attracted to moist soil and decaying organic matter.
• How to fix/prevent it: Improve drainage and avoid overwatering. You can also use sticky traps to catch adult flies.

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. Be sure to provide adequate wind protection and avoid overwatering. Choose a sunny location with well-drained soil to help your plants thrive.

Nasturtiums are great companion plants for many garden vegetables in the Great Plains. They attract beneficial insects and can even act as a trap crop for aphids, protecting other plants from infestation.

Good companions include tomatoes, cucumbers, and squash. Nasturtiums help repel pests that attack these vegetables. They also do well with broccoli and cabbage, as they deter cabbage moths. Avoid planting nasturtiums near fennel, as they can inhibit each other's growth.