Lobelia in Zone 6B — Mid-Atlantic

Lobelia is a fantastic addition to any Mid-Atlantic garden, bringing a splash of vibrant blue to borders, containers, and hanging baskets. Its delicate, trailing habit softens edges and adds a touch of elegance, while its continuous blooms provide lasting color throughout our humid summers and into the cooler days of fall.

Don't let our region's challenges deter you. While we deal with humidity, deer, and the occasional Japanese beetle, the 198-day growing season in Zone 6B gives you plenty of time to enjoy thriving Lobelia with a little planning and care.

Starting Lobelia from seed indoors is an option, but it can be tricky due to the tiny size of the seeds and their slow initial growth. If you're up for the challenge, begin in early to late February, about 10 weeks before you plan to transplant outdoors.

Use seed trays with a fine-grained seed starting mix. Bottom watering can help prevent damping off, a common issue when seedlings are overcrowded and the air is humid. Provide consistent warmth and bright light, and be patient – Lobelia seedlings can be slow to get going. Given the potential challenges, many Mid-Atlantic gardeners find it easier to purchase established Lobelia starts from a local nursery.

Transplant your Lobelia seedlings (or starts) outdoors in late April through late May, after the danger of late frost has passed. Before transplanting, be sure to harden them off by gradually exposing them to outdoor conditions for about a week.

Space plants 4-6 inches apart to allow for their spreading growth habit. Keep an eye on the weather forecast during this time, as unexpected cold snaps can still occur in the Mid-Atlantic. If frost threatens, cover your young plants with a frost blanket.

Lobelia needs consistent moisture, especially during our humid summers. The key is to keep the soil evenly moist, but not waterlogged. Lobelia is not drought-tolerant and will suffer if allowed to dry out completely.

During the spring and fall, when temperatures are cooler and rainfall is more frequent, you may only need to water once or twice a week. However, during the heat of summer, increase watering to every other day or even daily, depending on rainfall. Stick your finger about 2 inches deep into the soil. If it feels dry to the touch, it's time to water. Aim for about an inch of water per week, either from rainfall or irrigation. Watering at the base of the plant is preferable, especially in our humid climate, to minimize the risk of fungal diseases.

Signs of underwatering include wilting leaves and dry, crispy edges. Overwatering can lead to yellowing leaves and root rot. Applying a layer of mulch around your Lobelia plants can help retain moisture in the soil and regulate soil temperature, which is especially beneficial during our hot summers.

Lobelia requires minimal pruning, but a little attention can encourage continued blooms. As the summer progresses, you might notice that flowering slows down, particularly during the hottest spells.

When this happens, shear back the plants by about half. Don't worry, they'll bounce back! This encourages fresh growth and a new flush of flowers as the weather cools down in the fall. As the first frost approaches in late October, there's no need to prune further. Simply let the plants die back naturally.

Lobelia isn't a plant you typically "harvest" in the traditional sense. Instead, enjoy its masses of tiny blue flowers as part of your garden display. Since Lobelia blooms continuously, you'll find it flowering from late June through mid-August, and often well beyond with proper care.

There's no need to pick the flowers; simply deadhead any spent blooms to encourage more production. Keep an eye on the plants as the first frost approaches in late October. While the flowers won't continue to develop, you can still enjoy their beauty until the cold weather arrives.

Here are some common problems you might encounter growing Lobelia in the Mid-Atlantic:

Dies back in extreme heat:

• What it looks like: The plant wilts, leaves turn brown and crispy, and overall growth slows down or stops entirely.
• What causes it: Prolonged periods of high temperatures, especially when combined with humidity, can stress Lobelia.
• How to fix/prevent it: Provide afternoon shade, especially during the hottest part of the summer. Ensure consistent watering, and consider moving container plants to a cooler location.

Damping off from overwatering:

• What it looks like: Seedlings suddenly collapse and die, often with a fuzzy, grayish mold on the soil surface.
• What causes it: Overwatering, poor drainage, and high humidity create ideal conditions for fungal diseases that cause damping off.
• How to fix/prevent it: Use a well-draining seed starting mix. Water seedlings from the bottom to avoid wetting the foliage. Ensure good air circulation.

Slugs:

• What it looks like: Irregular holes in leaves, especially on low-growing plants. Silvery slime trails on leaves and soil. Damage is worse at night and in wet weather.
• What causes it: Slugs are gastropods that feed at night in moist conditions. They hide under mulch, boards, and debris during the day.
• How to fix/prevent it: Use beer traps (shallow dish of beer sunk into soil). Apply iron phosphate bait (pet-safe). Remove hiding spots. Water in the morning so the soil surface dries by evening. Consider using copper tape around beds or diatomaceous earth around plants.

Mid-Atlantic Specific Challenges: The moderate-to-hot heat and humid humidity of our summers mean that Lobelia can be susceptible to heat stress and fungal diseases. Even rainfall means that proper watering and drainage are critical.

Lobelia makes a great companion plant in the Mid-Atlantic garden. Its delicate foliage and blooms contrast nicely with larger plants like tomatoes and peppers, attracting pollinators that benefit these crops. Planting Lobelia near lettuce can also help to deter slugs, which can be a problem in our humid climate.

Avoid planting Lobelia near aggressive, sprawling plants that might outcompete it for resources.