Nasturtium in Zone 6B — Midwest

Nasturtiums are a fantastic addition to any Midwest garden, offering peppery-flavored leaves and vibrant flowers that brighten up salads and garden beds alike. They're also incredibly versatile, thriving in our fertile soil and providing a satisfying harvest from mid-summer right up until those first frosts threaten.

While we know Midwest weather can be unpredictable – with temperature swings in spring and occasional summer heat spells – Nasturtiums are surprisingly resilient. Our 183-day growing season gives you plenty of time to enjoy these beauties, especially if you time your planting right.

Starting Nasturtium indoors isn't essential here in the Midwest, given our reliable summer heat, but it can give you a head start, especially if you're aiming for an early bloom. Begin your indoor sowing from mid-March through early April, about four weeks before you plan to transplant.

Use seed trays with good drainage and a quality seed-starting mix. Keep the trays warm and provide plenty of light – a sunny windowsill or grow lights work well. Don't forget to water from the bottom to encourage strong root growth. This helps avoid damping off, a common issue in our moderate-to-late spring.

Transplanting Nasturtiums in the Midwest should happen after the danger of frost has passed, generally from late April through mid-May. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

When transplanting, space them about 10-12 inches apart to allow for their trailing growth habit. Keep an eye on the weather forecast – a late frost can still occur in our region, so be prepared to cover your young plants if needed.

Direct sowing is the preferred method for Nasturtiums, as they don't always love being transplanted. Wait until after the last frost, typically late April, but you can sow seeds all the way through early August for a continuous supply of flowers and leaves.

Prepare your soil by loosening it and removing any large clumps. Plant seeds about half an inch deep, spacing them 10-12 inches apart. Nasturtiums aren't picky about soil, but good drainage is key. They'll germinate best when the soil temperature is consistently warm, so keep an eye on those Midwest weather patterns.

Nasturtiums are wonderfully low-maintenance when it comes to watering, which is a blessing during our busy Midwest summers. They actually thrive in slightly poor, dry soil. Too much water or fertilizer will encourage leaf growth at the expense of those beautiful, edible flowers.

During our typically wet summers, you might not need to water them much at all, especially if you get regular rainfall. Use the "finger test" – stick your finger about two inches deep into the soil. If it feels dry, it's time to water. Aim for about an inch of water per week, either from rainfall or irrigation. Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our moderate-to-humid conditions.

Signs of underwatering include wilting leaves and stunted growth. Overwatering, on the other hand, can lead to yellowing leaves and root rot. A light layer of mulch around the base of the plants can help retain moisture and suppress weeds, but don't overdo it – you want the soil to dry out between waterings.

You can expect your first harvest of Nasturtium leaves and flowers starting in mid-June, about 55 days after planting. Keep harvesting right through mid-October, until the first frost. The flowers are ready to pick when they are fully open and vibrant in color.

To harvest, simply snip the stems of the flowers or leaves with scissors or your fingers. Regular harvesting encourages continued production of both flowers and leaves. Don't forget to harvest the seed pods as well – they can be pickled and used like capers.

As the end of the season approaches and you anticipate that first frost, harvest as many flowers and leaves as you can. You can even try to overwinter some seeds for next year's planting.

Here are three common problems you might encounter with Nasturtiums in your Midwest garden:

Aphids (intentional trap crop)

• What it looks like: Clusters of tiny green, black, or white insects on stems and undersides of leaves. Leaves may be sticky or distorted.
• What causes it: Aphids are attracted to Nasturtiums, which can be used as a trap crop to draw them away from other plants. Warm, humid conditions can exacerbate infestations.
• How to fix/prevent it: Regularly inspect your plants. A strong blast of water from the hose can dislodge aphids. Introduce beneficial insects like ladybugs. Since Nasturtiums are a trap crop, you can tolerate some aphids – they're doing their job!

Cabbage Caterpillars

• What it looks like: Holes in leaves, often with green or brown droppings nearby. You may see small green caterpillars on the plant.
• What causes it: Cabbage white butterflies lay their eggs on Nasturtiums, and the caterpillars hatch and feed on the leaves. These are more common during our moderate-to-hot Midwest summers.
• How to fix/prevent it: Handpick caterpillars off the plants. Cover plants with netting to prevent butterflies from laying eggs. Bacillus thuringiensis (Bt) is an effective organic control.

Black Fly

• What it looks like: Small, black, fly-like insects clustered on new growth and flower buds. Stunted growth and distorted leaves.
• What causes it: Black flies are attracted to stressed plants. They thrive in humid conditions, which we often experience in the Midwest.
• How to fix/prevent it: Ensure good air circulation around your plants. Water regularly but avoid overwatering. Insecticidal soap can be used to control infestations.

Midwest Specific Challenges: The moderate-to-hot heat and moderate-to-humid humidity of a Midwest summer can create ideal conditions for pests and diseases. Regular monitoring and proactive measures are key to keeping your Nasturtiums healthy and productive. Also, our wet-summer rainfall means you must be vigilant about drainage.

Nasturtiums are great companions for several plants in your Midwest garden:

• Tomato: Nasturtiums repel tomato hornworms and whiteflies, protecting your tomato plants from these common pests.
• Cucumber: Nasturtiums deter cucumber beetles, which can damage cucumber vines and spread disease.
• Squash: Similar to cucumbers, Nasturtiums help keep squash bugs and squash vine borers away from your squash plants.
• Broccoli and Cabbage: Nasturtiums attract cabbage white butterflies, acting as a trap crop and drawing them away from your broccoli and cabbage.

Avoid planting Nasturtiums near fennel, as they can inhibit each other's growth.