Nasturtium in Zone 6A — Midwest

Nasturtiums are a fantastic addition to any Midwest garden. The peppery flavor of the leaves and flowers adds a unique zest to salads, and they're beautiful trailing from containers or spilling over garden beds. Plus, they attract beneficial insects while potentially acting as a trap crop for pests, making them a valuable ally in our fertile soil.

While Midwest weather can be unpredictable, with late frosts in spring and the occasional summer heat spell, nasturtiums are surprisingly resilient. With a little attention to timing within our 178-day growing season, you can enjoy a bountiful harvest of these vibrant, edible flowers.

Starting nasturtiums indoors is possible, but honestly, direct sowing is usually the way to go here in the Midwest. Nasturtiums don't love having their roots disturbed, so transplanting can be a bit tricky. However, if you're eager to get a head start, or if you want to ensure blooms as early as possible, starting indoors is a viable option.

If you choose to start indoors, begin in late March through mid April, about four weeks before you plan to transplant. Use seed trays with good drainage and a well-draining potting mix. Keep the soil consistently moist (bottom watering helps prevent damping off) and provide plenty of light, either from a sunny window or a grow light. Given our moderate-to-late springs, starting indoors can give you a jump on the season.

Transplanting nasturtiums outdoors should happen in late April through late May, once the danger of frost has passed. Before transplanting, be sure to harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind, preventing transplant shock.

When transplanting, space your nasturtiums 10-12 inches apart. Our Midwest springs can be variable, so keep an eye on the weather forecast and be prepared to cover your seedlings if a late frost is predicted.

Direct sowing is the preferred method for nasturtiums in the Midwest, as they really don't like having their roots disturbed. Wait until late April through early August, after any chance of frost, to sow your seeds directly into the garden. The soil temperature should be at least 55°F for best germination.

Prepare your soil by loosening it and removing any weeds. Nasturtiums aren't fussy and actually thrive in slightly poor soil, so no need to add too much fertilizer. Sow the seeds about ½ inch deep and 10-12 inches apart. Keep the soil consistently moist until the seedlings emerge.

Nasturtiums are surprisingly drought-tolerant and thrive on neglect, which is perfect for busy Midwest gardeners. The key is to avoid overwatering, as this can lead to more foliage and fewer flowers. Remember our summers can bring moderate-to-hot heat with moderate-to-humid humidity, plus wet-summer rainfall.

During the spring, when rainfall is usually plentiful, you might not need to water your nasturtiums at all, unless we're experiencing an unusually dry spell. Once summer heat spells arrive, check the soil moisture by sticking your finger about 2 inches deep. If the soil feels dry, it's time to water. Generally, an inch of water per week, whether from rain or irrigation, is sufficient. Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our moderately humid climate.

Signs of underwatering include wilting leaves and stunted growth. Overwatering, on the other hand, can cause yellowing leaves and root rot. A light layer of mulch, like shredded bark, can help retain moisture in the soil and suppress weeds, but don't overdo it, as nasturtiums prefer well-drained conditions.

You can expect your first harvest of nasturtium flowers and leaves in late June through mid October, about 55 days after planting. The flowers are ready to harvest when they are fully open and brightly colored. The leaves can be harvested at any time. Even the seed pods can be harvested and pickled for a caper-like treat.

To harvest, simply snip off the flowers or leaves with scissors or your fingers. Be gentle to avoid damaging the plant. Regular harvesting encourages continued production, so don't be shy about picking those blooms! As our first frost approaches in mid- October, harvest any remaining flowers and leaves to enjoy before the cold weather sets in. You can even let some of the seed pods mature and dry on the plant to collect seeds for next year's garden.

Here in the Midwest, we can face a few common problems with nasturtiums, but they're generally easy to manage. The top culprits are aphids, cabbage caterpillars, and black fly.

Aphids *What it looks like:* Small, pear-shaped insects clustered on stems and leaves, often accompanied by sticky honeydew and sooty mold. *What causes it:* Aphids thrive in warm, dry conditions, but can also be attracted to plants that are stressed or over-fertilized. Our variable spring weather can sometimes weaken plants, making them more susceptible. *How to fix/prevent it:* Nasturtiums can actually be used as a trap crop for aphids, drawing them away from other plants. If infestations are heavy, spray with a strong jet 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. *How to fix/prevent it:* Handpick the caterpillars off the plants or use Bacillus thuringiensis (Bt), a biological insecticide. Row covers can also prevent the butterflies from laying eggs on the plants.

Black Fly *What it looks like:* Tiny black flies clustered around new growth. *What causes it:* Similar to aphids, they like stressed plants. *How to fix/prevent it:* Treat like aphids, and make sure you're not overwatering.

Midwest Specific Challenges: Our moderate-to-hot heat, moderate-to-humid humidity, and wet-summer rainfall can create conditions that favor both pests and diseases. Good air circulation and avoiding overwatering are key to keeping your nasturtiums healthy and productive.

Nasturtiums are great companions for many plants in your Midwest garden. They attract beneficial insects and can even repel some pests.

Good companions include:

• Tomatoes: Nasturtiums can help deter tomato hornworms and other pests.
• Cucumbers: They can help repel cucumber beetles.
• Squash: Nasturtiums can attract pollinators, which are essential for squash production.
• Broccoli and Cabbage: They can act as a trap crop for cabbage white butterflies, protecting these brassicas from cabbage caterpillars.

There aren't really any bad companions for nasturtiums, but be mindful of their trailing growth habit. Avoid planting them too close to smaller, more delicate plants that they might smother.