Nasturtium in Zone 7A — Midwest

Nasturtiums are a fantastic addition to any Midwest garden. Their peppery leaves and vibrant flowers add a unique flavor to salads and a pop of color to your garden. Plus, they're incredibly easy to grow, making them a rewarding choice for gardeners of all levels in our fertile soil.

While Midwest weather can be unpredictable, with our variable springs and occasional summer heat spells, Nasturtiums are quite adaptable. With our long 193-day growing season, you have plenty of time to get them established and enjoy their bounty.

Starting Nasturtiums indoors isn't usually necessary in the Midwest, as they prefer direct sowing. However, if you're eager to get a head start, you can start seeds indoors from mid-March through early April. This gives you about four weeks to nurture them before transplanting.

Use seed trays with a good quality potting mix and ensure they have warmth and plenty of light. Bottom watering is especially helpful to keep the soil consistently moist without overwatering. Keep in mind that our springs can be moderate-to-late, so don't rush the process.

Transplanting Nasturtiums outdoors should be done from mid-April through mid-May, after the danger of frost has passed. Before transplanting, be sure to harden off your seedlings. This means gradually exposing them to outdoor conditions for about a week.

When transplanting, space the plants about 10-12 inches apart. Keep an eye on the Midwest weather forecast during this time; a late frost can still happen, so be prepared to cover your young plants if needed.

Direct sowing is the recommended method for growing Nasturtiums in the Midwest, as they don't always love being transplanted. You can sow seeds directly into your garden from mid-April through mid-August. This gives you a nice long window to get them started.

Choose a spot with full sun to partial shade and prepare the soil by loosening it and removing any large clumps. Plant seeds about half an inch deep, spacing them 10-12 inches apart. Nasturtiums germinate best when the soil temperature is consistently warm, so aim for sowing after any late spring cold snaps.

Nasturtiums are wonderfully low-maintenance when it comes to watering, thriving in conditions that would make other plants wilt. Given our wet-summer climate in the Midwest, overwatering is a bigger concern than underwatering. Less is definitely more with these plants.

During the spring, when rainfall is more frequent, you might not need to water them at all unless we have a particularly dry spell. In the summer, especially during those moderate-to-hot heat spells, check the soil moisture by using the "finger test"—stick your finger about two inches deep into the soil. If it feels dry, give them about an inch of water per week, watering at the base of the plants to avoid wetting the leaves and encouraging fungal diseases in our moderate-to-humid conditions.

Signs of underwatering include wilting leaves and stunted growth, while overwatering can lead to yellowing leaves and root rot. Mulching around the base of the plants can help retain moisture and regulate soil temperature, but use a light touch; too much mulch can trap excess moisture and cause problems.

You can expect your first Nasturtium harvest starting around mid-June and continuing through mid-October in the Midwest. These plants mature quickly, usually around 55 days from planting. Both the flowers and leaves are edible, so you have a lot of options.

Harvest the flowers when they are fully open for the best flavor and visual appeal. To keep the plant producing, harvest regularly, which encourages more blooms. As the season winds down and we approach our first frost around mid-October, harvest any remaining flowers and leaves. Don't forget the seed pods – they can be pickled for a caper-like treat!

Nasturtiums are generally easy to grow, but here are a few common problems you might encounter in the Midwest:

Aphids

• What it looks like: Clusters of tiny green, black, or brown insects on stems and undersides of leaves, often causing distorted or yellowing foliage.
• What causes it: Aphids thrive in moderate temperatures and can multiply rapidly. Our Midwest summers, with moderate-to-humid conditions, can be ideal for them.
• How to fix/prevent it: Nasturtiums are often used as a trap crop for aphids, drawing them away from other plants. If infestations are heavy, spray plants with a strong blast of water or use insecticidal soap.

Cabbage Caterpillars

• What it looks like: Green caterpillars that chew holes in leaves, leaving behind droppings.
• What causes it: These caterpillars are the larvae of cabbage white butterflies, which are common in the Midwest. They love to feed on plants in the cabbage family, but will also munch on nasturtiums.
• How to fix/prevent it: Handpick caterpillars off plants. You can also use Bacillus thuringiensis (Bt), a biological insecticide, to control them.

Black Fly

• What it looks like: Small black flies clustered on new growth, causing stunted or distorted leaves.
• What causes it: Black flies, like aphids, are attracted to stressed plants and can multiply quickly in warm, humid conditions.
• How to fix/prevent it: Improve air circulation around plants and avoid overwatering. Insecticidal soap can also be effective.

Midwest Specific Challenges: The combination of moderate-to-hot heat, moderate-to-humid humidity, and wet-summer rainfall in the Midwest can create ideal conditions for pests and diseases. Regularly inspect your plants, provide good air circulation, and avoid overwatering to keep your Nasturtiums healthy.

Nasturtiums make excellent companion plants in the Midwest garden. They can help protect other vegetables and attract beneficial insects.

Good companions include tomatoes, cucumbers, and squash. Nasturtiums deter pests like aphids and squash bugs, protecting these crops. They also benefit broccoli and cabbage by attracting cabbage white butterflies away from them. Avoid planting nasturtiums near fennel, as they can inhibit each other's growth.