Nasturtium in Zone 3B — Midwest

Nasturtiums are fantastic for Midwest gardens. Their peppery flavor brightens salads, the flowers are gorgeous, and they thrive in our fertile soil with adequate summer rain. Plus, they're easy to grow, bringing a lot of satisfaction with minimal effort.

Our Midwest weather can be unpredictable, with late frosts and summer heat spells, but nasturtiums are quick to mature. With a 118-day growing season, you'll have plenty of time to enjoy these beauties if you time your planting right.

Starting nasturtiums indoors is possible, but honestly, it's not usually necessary here in the Midwest. Since they resent transplanting, direct sowing is generally preferred. That said, if you're eager to get a head start, you can sow seeds indoors from late April through mid May – about four weeks before you plan to transplant.

Use seed trays with a good seed-starting mix and keep them warm and well-lit. Bottom watering helps prevent damping off. Keep in mind that our spring can be variable, so watch for late frost even if you start indoors.

If you started your nasturtiums indoors, aim to transplant them outdoors from late May through late June, after the danger of frost has passed. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Midwest weather.

Space the plants 10-12 inches apart. Keep an eye on the weather forecast – a sudden cold snap can still happen, even in late May.

Direct sowing is the way to go for nasturtiums in the Midwest! Wait until late May through early July, after any chance of frost. Prepare the soil by loosening it and removing any weeds. Nasturtiums aren't picky about soil fertility, so don't worry about amending it too much.

Sow seeds 1/2 inch deep and space them 10-12 inches apart. Keep the soil consistently moist until the seedlings emerge.

Nasturtiums are pretty low-maintenance when it comes to watering, which is great for us Midwest gardeners. They actually thrive in slightly poor, dry soil. Overwatering or over-fertilizing encourages leaf growth at the expense of flowers, so less is definitely more.

During the hotter summer months, especially during heat spells, check the soil moisture regularly. Use the "finger test" – stick your finger about 2 inches into the soil. If it feels dry, it's time to water. Aim for about 1 inch of water per week, including rainfall. With our moderate-to-humid summers, it's best to water at the base of the plant to avoid fungal diseases.

Yellowing leaves can be a sign of overwatering, while wilting leaves indicate underwatering. A light layer of mulch can help retain moisture and suppress weeds, which is helpful in our wet-summer climate.

You can expect your first nasturtium harvest from late July through mid September, about 55 days after planting. The flowers, leaves, and seed pods are all edible. Harvest the 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, being careful not to damage the plant. Regular harvesting encourages continued production. As our first frost approaches in mid- September, harvest any remaining flowers and seed pods. The seed pods can be pickled for a caper-like treat.

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

Aphids

• What it looks like: Small, soft-bodied insects clustered on stems and leaves, often accompanied by sticky honeydew.
• What causes it: Aphids are attracted to stressed plants, and our variable spring weather can sometimes weaken them.
• How to fix/prevent it: Nasturtiums can actually be used as a trap crop for aphids, drawing them 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 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 a biological insecticide like Bacillus thuringiensis (Bt).

Black Fly

• What it looks like: Tiny black flies that suck sap from the leaves, causing them to yellow and curl.
• What causes it: Black flies thrive in warm, humid conditions.
• How to fix/prevent it: Introduce beneficial insects like ladybugs, which prey on black flies. Insecticidal soap can also be effective.

Midwest Specific Challenges: Our moderate-to-hot summers with moderate-to-humid humidity and wet-summer rainfall can create ideal conditions for pests and fungal diseases. Regular monitoring and prompt action are key to keeping your nasturtiums healthy.

Nasturtiums are great companions for many plants in the Midwest garden. They attract beneficial insects and can even act as a trap crop for pests.

Good companions include tomatoes, cucumbers, and squash because they deter pests that bother those veggies. They also work well with broccoli and cabbage, drawing cabbage white butterflies away from those crops. Avoid planting nasturtiums near fennel, as they can inhibit each other's growth.