Lobelia in Zone 7B — Pacific Northwest

Lobelia is a charming addition to any Pacific Northwest garden, offering a profusion of delicate blue flowers that spill beautifully from containers and borders. Their cool, vibrant color complements our region's lush greenery and provides a delightful contrast to the overcast spring days. The cool nights we often experience even in summer seem to intensify their color, making them a true standout.

While we enjoy mild summers here in Zone 7B, our springs can be slow to warm up, and slugs are always a concern. Fortunately, by starting seeds indoors at the right time and taking precautions against these common pests, you can easily enjoy these blooms throughout our long, mild fall. With our 193-day growing season, there's plenty of time to nurture these beauties.

Starting Lobelia from seed indoors is best reserved for experienced gardeners. Lobelia seeds are incredibly tiny, and the seedlings grow slowly, making them a bit challenging. That said, if you're up for the task, start your seeds indoors from mid-February through early March.

Use seed trays with a fine-grained seed starting mix. Gently press the seeds onto the surface – don't bury them. Bottom watering is key to avoid disturbing the tiny seeds. Keep the trays warm (around 70°F) and provide ample light, either from a sunny window or grow lights. Remember, our spring weather is often cool and overcast, so supplemental lighting is usually needed.

Transplant your Lobelia seedlings outdoors from late April through late May, once the danger of frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the cooler temperatures and stronger sunlight.

Plant them 4-6 inches apart in well-draining soil. Even though we're past the typical frost date, keep an eye on the forecast – those late spring temperature swings can still surprise you! Given the tiny size of the seedlings and their slow growth, many PNW gardeners find it easier to simply purchase Lobelia starts from a local nursery.

Lobelia thrives with consistent moisture, which is especially important during our dry summer months. While we don't usually experience extreme heat here, our summers are still dry, and Lobelia is not drought-tolerant. Aim to keep the soil consistently moist, but not waterlogged.

During the wet springs, you likely won't need to water much at all. Once the dry summer months arrive, check the soil moisture regularly using 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 from rainfall or irrigation. Water at the base of the plants to avoid wetting the foliage excessively, which can encourage fungal diseases.

Signs of underwatering include wilting leaves and dry, crispy edges. Overwatering can lead to yellowing leaves and root rot. A light layer of mulch, like shredded bark, can help retain moisture and regulate soil temperature, which is beneficial in our variable climate.

Lobelia requires minimal pruning, but a little attention can keep them blooming beautifully throughout the season. The key is to shear them back when flowering slows down, which typically occurs in midsummer. This encourages a fresh flush of growth and more blooms in the cooler fall weather we often enjoy.

Simply shear the plants back by about half, removing spent flowers and any leggy growth. Don't be afraid to be a little aggressive – they'll bounce back quickly. As the first frost approaches in late October, you can let the plants go and remove them after they've completely died back.

Lobelia is primarily grown for its ornamental value, so there's no real "harvest" in the traditional sense. You can expect the first masses of tiny blue flowers to appear from early July through late August, about 65 days after transplanting. Enjoy them as a beautiful addition to your garden!

The key is to deadhead spent flowers regularly to encourage continuous blooming. Simply pinch off the faded blooms to keep the plants looking tidy and promote new growth. As the first frost approaches in late October, you can simply enjoy the last of the blooms before the plants naturally fade with the cooler temperatures.

Lobelia can encounter a few common problems in the Pacific Northwest:

Dies Back in Extreme Heat

• What it looks like: The plant wilts, leaves turn brown and crispy, and flowering stops.
• What causes it: While our summers are mild, occasional heat spikes can stress Lobelia. Our dry summer conditions exacerbate the issue.
• How to fix/prevent it: Provide afternoon shade during the hottest part of the day. Water deeply and consistently during heat waves. Consider moving container plants to a cooler location.

Damping Off from Overwatering

• What it looks like: Seedlings suddenly collapse and die, often with a white, fuzzy mold visible on the soil surface.
• What causes it: Overwatering creates a favorable environment for fungal diseases that attack young seedlings. Our wet springs can contribute to this problem.
• How to fix/prevent it: Use a well-draining seed starting mix. Water from the bottom to avoid wetting the foliage. 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 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.

Pacific Northwest Specific Challenges: Our mild heat and dry-summer rainfall can present a unique set of challenges for Lobelia. While they appreciate the consistent moisture, it's crucial to avoid overwatering, especially during our wet springs. The dry summer months require consistent watering to prevent them from drying out, but providing some afternoon shade can help them cope with occasional heat spikes.

Lobelia makes an excellent companion plant for several vegetables in the Pacific Northwest garden. Planting them near tomatoes and peppers can help attract beneficial insects, like hoverflies, which prey on aphids that can plague these warm-season crops. The vibrant blue flowers also attract pollinators, which can improve fruit set.

Lobelia also pairs well with lettuce, providing a bit of shade that can help prevent bolting during warmer spells. Avoid planting them near aggressive, sprawling plants that might compete for resources or block sunlight.