Lobelia in Zone 3B — Great Plains

Lobelia is worth including in your Great Plains garden for its dazzling blue flowers that provide a vibrant contrast to the greens and yellows of other plants. This compact, spreading plant is perfect for edging beds, filling containers, or cascading from hanging baskets, bringing a touch of elegance to your outdoor spaces. Plus, its long bloom time provides continuous color throughout the summer months, making it a delightful addition to any garden display.

While our region presents challenges like extreme temperature swings and variable rainfall, Lobelia's relatively quick maturity makes it a manageable choice, even with our shorter 118-day growing season. With a little planning and attention, you can enjoy these beautiful blooms from midsummer until the first frosts arrive.

Starting Lobelia indoors can give you a jump on the season, but it's not always necessary, and honestly, these tiny seeds are a pain. If you're up for the challenge, aim to start seeds mid-March through early April, about 10 weeks before you plan to transplant them outdoors. This timing works well with our variable spring weather.

Use seed trays with a fine-grained seed starting mix. Since the seeds are so small, surface sow them and gently mist with water. Keep the trays consistently moist by bottom watering – set the tray in a shallow dish of water and let the soil absorb moisture from the bottom. Provide warmth (around 70°F) and plenty of light, either from a sunny window or grow lights.

Transplant your Lobelia seedlings outdoors in early to late June, once the risk of frost has passed. Given the tiny seeds and slow growth, consider buying starts from a local nursery to save yourself some headache. Before transplanting, harden off the seedlings by gradually exposing them to outdoor conditions for about a week.

Choose a location with full sun to part shade and space the plants 4-6 inches apart. Even in June, we can still get some wild temperature swings, so keep an eye on the forecast and be prepared to cover the seedlings if a late frost threatens.

Lobelia needs consistent moisture to thrive, which can be a challenge in our Great Plains climate with its hot summers and variable rainfall. During the peak of summer, you'll likely need to water deeply several times a week, especially if rainfall is scarce. Use 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, either through rainfall or irrigation. Water at the base of the plants to avoid wetting the foliage, which can help prevent fungal diseases in our low-to-moderate humidity. Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to yellowing leaves and root rot.

Mulching around your Lobelia plants with a layer of shredded bark or compost can help retain moisture in the soil, reduce evaporation, and suppress weeds.

Lobelia requires minimal pruning, but a little attention can keep them looking their best. When flowering slows down in midsummer, shear back the plants by about half. This encourages fresh growth and a new flush of flowers as the weather cools in late summer and early fall.

Simply use a pair of scissors or pruning shears to trim back the entire plant, removing spent flowers and any leggy growth. Don't be afraid to cut them back quite a bit – they'll bounce back quickly. As the first frost approaches around mid- September, you can let the plants go and allow them to die back naturally.

Lobelia is primarily grown for its ornamental value, so there's no real "harvest" in the traditional sense. Instead, you'll be enjoying the masses of tiny blue flowers that adorn the plants from early August through mid-September.

The continuous bloom of Lobelia provides a beautiful display throughout the summer months, adding color and charm to your garden. To encourage continued production, deadhead spent flowers regularly by pinching them off with your fingers. As the first frost approaches in mid- September, the plants will naturally begin to decline, signaling the end of their season.

Here are three common problems you might encounter with Lobelia in the Great Plains:

Dies Back in Extreme Heat

• What it looks like: The plant wilts, leaves turn brown and crispy, and growth stops or the plant appears to die.
• What causes it: Prolonged periods of high heat and low moisture stress the plant.
• How to fix/prevent it: Provide afternoon shade, especially during the hottest part of the summer. Ensure consistent watering and consider using shade cloth during heat waves.

Damping Off From Overwatering

• What it looks like: Seedlings suddenly wilt and collapse at the soil line, often covered in a white, fuzzy mold.
• What causes it: Fungal disease thrives in overly moist conditions, especially with poor air circulation.
• How to fix/prevent it: Use a sterile seed starting mix, ensure good air circulation around seedlings, and avoid overwatering. Bottom watering can help prevent this issue.

Slugs

• What it looks like: Irregular holes in leaves, especially low-growing plants. Silvery slime trails on leaves and soil. Damage worse at night and in wet weather.
• What causes it: Gastropods that feed at night in moist conditions. Hide under mulch, boards, and debris during the day.
• How to fix/prevent it: Beer traps (shallow dish of beer sunk into soil). Iron phosphate bait (pet-safe). Remove hiding spots. Water in morning so soil surface dries by evening. Copper tape around beds. Diatomaceous earth around plants.

Great Plains Specific Challenges: Our combination of intense summer heat, low-to-moderate humidity, and variable rainfall can be tough on Lobelia. Consistent watering is crucial, but be mindful of overwatering, especially during cooler periods. Provide some afternoon shade to protect the plants from the harshest heat.

Lobelia works well with several companions in the Great Plains garden. Plant it near tomatoes and peppers to attract pollinators, which will improve fruit set. The bright blue flowers also contrast beautifully with the red and green foliage of these vegetables.

Lettuce also benefits from being planted near Lobelia. The spreading habit of Lobelia helps to shade the soil, keeping it cooler and more moist, which is ideal for lettuce. Avoid planting Lobelia near aggressive spreaders that will compete for resources.