Lobelia in Zone 6B — Southeast

Lobelia's masses of vibrant blue flowers make it a fantastic addition to any Southeast garden. It adds a lovely pop of color to borders and containers, and its spreading habit makes it ideal for filling in gaps. It’s a great way to add visual interest during our long summer.

While the hot and humid summers here can be a challenge, starting Lobelia at the right time allows you to enjoy its beauty before the worst of the heat sets in. Our long 208-day growing season gives you plenty of opportunity for success.

Starting Lobelia indoors can be a bit tricky due to its tiny seeds and slow initial growth. Honestly, you might have better luck buying starts from a local nursery, but if you're up for the challenge, go for it!

If you decide to start from seed, aim for early to late February, about 10 weeks before you plan to transplant. Use seed trays with a good seed-starting mix, and keep them consistently moist using bottom watering to avoid disturbing the tiny seeds. Provide warmth and plenty of light; a grow light is really helpful here in our moderate Southeast spring.

Transplant your Lobelia seedlings outdoors from mid April through mid May, after the danger of frost has passed. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This will help them adjust to the sun and wind.

Space your plants 4-6 inches apart. Keep an eye on the weather forecast during this time; those late-season cool snaps can still happen. Given our clay soil, amending the planting area with compost will improve drainage and give your Lobelia a good start.

Lobelia needs consistent moisture, especially during our hot and humid summers. Aim to keep the soil consistently moist but not waterlogged. Lobelia really doesn't tolerate drought, and it might even go dormant if it gets too dry, although it usually bounces back when the weather cools.

During the hotter months, you’ll likely need to water deeply several times a week. Stick your finger about 2 inches into the soil; if it feels dry, it’s time to water. Depending on rainfall, that could mean giving them around an inch of water per week. Water at the base of the plants to avoid getting the foliage wet, which can increase the risk of fungal diseases in our humid climate. Signs of underwatering include wilting leaves, while overwatering can lead to yellowing leaves and root rot.

Mulching around your Lobelia plants with pine straw or shredded bark will help retain moisture and keep the soil cooler, which is especially helpful during our long summers.

Lobelia benefits from minimal pruning to keep it looking its best. When flowering slows down in midsummer, shear the plants back by about half. This encourages fresh growth and a new flush of flowers as the weather cools down in the fall.

Use sharp, clean shears to make your cuts. As the first frost approaches in late October, you can let the plants fade naturally, or you can cut them back to tidy up the garden.

With Lobelia, you won't be harvesting fruits or vegetables; you're harvesting beauty! Expect the first masses of tiny blue flowers in late June through mid August, about 65 days after planting.

Enjoy the flowers in your garden and appreciate the continuous blooms throughout the season. Deadheading spent flowers can encourage more blooms, but it's not strictly necessary. As the first frost approaches in late October, simply enjoy the last blooms before the plants fade.

Here are some common problems you might encounter with Lobelia in the Southeast:

Dies back in extreme heat

• What it looks like: The plant wilts, leaves turn brown and crispy, and overall growth slows or stops entirely.
• What causes it: Our intense summer heat can be too much for Lobelia, especially if it's not getting enough water.
• How to fix/prevent it: Provide afternoon shade, especially during the hottest part of the day. Ensure consistent watering, and consider mulching to keep the soil cooler.

Damping off from overwatering

• What it looks like: Seedlings suddenly collapse and die, often with a fuzzy white or gray mold on the soil surface.
• What causes it: Overwatering, especially in poorly drained soil, creates ideal conditions for fungal diseases to attack young seedlings.
• How to fix/prevent it: Use a well-draining seed-starting mix, water only when the soil surface is dry to the touch, and ensure good air circulation around seedlings.

Slugs

• What it looks like: Irregular holes in leaves, especially low-growing plants. Silvery slime trails on leaves and soil. Damage is worse at night and in wet weather.
• What causes it: Slugs thrive in moist conditions, which we certainly have here in the Southeast. They feed at night and hide during the day.
• How to fix/prevent it: Set out beer traps (shallow dishes of beer sunk into the soil). Use iron phosphate bait (pet-safe). Remove hiding spots like mulch and debris. Water in the morning so the soil surface dries by evening. Copper tape around beds can also deter slugs. Diatomaceous earth around plants works too.

Southeast Specific Challenges: Our hot and humid summers, combined with our wet-summer rainfall, can create a challenging environment for Lobelia. The humidity increases the risk of fungal diseases, and the heat can stress the plants. Proper watering, good air circulation, and afternoon shade are crucial for success.

Lobelia makes a great companion plant for several vegetables in the Southeast garden. It attracts pollinators, which can benefit your tomatoes and peppers. Plus, its low-growing habit can help suppress weeds around taller plants.

Lobelia also works well with lettuce. The lettuce can provide some shade for the Lobelia, while the Lobelia helps keep the soil moist for the lettuce. Avoid planting Lobelia near plants that require very dry soil, as its need for consistent moisture could create unfavorable conditions for those companions.