Nasturtium in Zone 5A — Midwest

Nasturtiums are more than just pretty flowers; they're a triple threat in the Midwest garden. The peppery leaves and vibrant blooms add a unique zing to salads, the entire plant thrives in our fertile soil, and they're incredibly satisfying to grow. Plus, they attract pollinators, which is always a win.

We know Midwest weather can be unpredictable, with variable springs and summer heat spells. But don't worry – Nasturtiums are fast growers. With our 157-day growing season, you'll have plenty of time to enjoy these beauties.

Starting Nasturtiums indoors is possible, but it's generally not the preferred method here in the Midwest. They really resent transplanting. However, if you're eager to get a head start, you can start seeds indoors from early to late April, about four weeks before you plan to move them outside.

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. Make sure to water from the bottom to avoid damping off. Given our moderate-to-late spring, starting indoors can give you a bit of a jump on the season, but direct sowing is usually easier.

If you started your Nasturtiums indoors, aim to transplant them outdoors from early May through early June. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Midwest weather.

Plant them 10-12 inches apart in well-draining soil. Keep an eye on the weather forecast – we sometimes get a late frost in early May, so be prepared to cover your seedlings if needed.

Direct sowing is the way to go with Nasturtiums in the Midwest. Wait until after the last expected frost, usually around early May, and then you can sow seeds directly into the garden from early May through late July.

Choose a spot with full sun to part shade and prepare the soil by loosening it and removing any weeds. Plant the seeds about ½ inch deep and 10-12 inches apart. Nasturtiums germinate best in soil that's around 65-70°F, so be patient if the weather is still cool.

Nasturtiums are pretty low-maintenance when it comes to watering, which is great for Midwest gardeners who have plenty of other things to worry about. They thrive in poor, dry soil, and too much water or fertilizer will encourage leaf growth at the expense of flowers. Remember, less is more with these guys.

During our moderate-to-hot summer heat spells, check the soil moisture by using the "finger test" – 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, especially during dry spells. Given our moderate-to-humid climate, it's best to water at the base of the plant to avoid fungal diseases.

Signs of underwatering include wilting leaves and dry, crispy edges. Overwatering can lead to yellowing leaves and root rot. Mulching around the plants can help retain moisture and keep the soil cool, which is beneficial during our summer heat.

You can expect your first Nasturtium harvest in early July and continue harvesting all the way through early October. The flowers, leaves, and seed pods are all edible, so there's plenty to enjoy! Harvest the flowers when they're fully open for the best flavor and visual appeal.

To harvest without damaging the plant, use scissors or your fingers to gently snip off the flowers or leaves. Regular harvesting encourages more blooms. As the first frost approaches in early October, harvest any remaining flowers and seed pods. You can pickle the seed pods for a caper-like treat to enjoy throughout the winter.

Here are a few common problems you might encounter with Nasturtiums in the Midwest:

Aphids:

• What it looks like: Tiny green, black, or brown insects clustered on stems and leaves, causing distorted growth.
• What causes it: Aphids are attracted to stressed plants, and our variable spring weather can sometimes weaken them.
• How to fix/prevent it: Nasturtiums are often used as a trap crop to draw aphids away from other plants. You can also blast them off with a strong stream of water from the hose.

Cabbage Caterpillars:

• What it looks like: Green caterpillars munching on leaves, leaving behind holes and droppings.
• What causes it: These caterpillars are the larvae of cabbage white butterflies, which are common in the Midwest.
• How to fix/prevent it: Handpick the caterpillars off the plants or use a natural insecticide like Bacillus thuringiensis (Bt).

Black Fly:

• What it looks like: Small black flies clustered around new growth.
• What causes it: These flies are attracted to young, tender plants, especially during periods of high humidity.
• How to fix/prevent it: Improve air circulation around the plants and use insecticidal soap to control infestations.

Midwest Specific Challenges: Our moderate-to-hot heat, moderate-to-humid humidity, and wet-summer rainfall can create ideal conditions for pests and diseases. Monitor your plants regularly and take action quickly to prevent problems from spreading.

Nasturtiums are great companion plants in the Midwest garden. They attract pollinators and can help deter pests from other crops:

• Tomato: Nasturtiums repel whiteflies and other pests that can bother tomatoes.
• Cucumber: They help protect cucumbers from squash bugs and cucumber beetles.
• Squash: Nasturtiums can act as a trap crop for aphids, keeping them away from squash plants.
• Broccoli and Cabbage: They deter cabbage moths, whose larvae can decimate brassica crops.

Avoid planting Nasturtiums near fennel, as it can inhibit their growth. Otherwise, they're pretty easygoing and get along well with most garden vegetables.