Lobelia in Zone 6A — Pacific Northwest

Lobelia, with its profusion of tiny, vibrant blue flowers, is a fantastic choice for adding a splash of color to your Pacific Northwest garden. The cool nights and mild summers we experience here actually intensify the flower color, making them even more stunning in hanging baskets or spilling over the edges of containers. Plus, they attract beneficial pollinators to your garden.

While we might struggle with heat-loving plants, Lobelia thrives in our climate, especially with a little attention. Our 148-day growing season gives you plenty of time to enjoy these beauties, and by starting seeds at the right time, or buying starts, you can easily overcome any potential challenges with our wet springs.

Starting Lobelia indoors in the PNW is an option, but honestly, it's often easier to buy starts from a local nursery. The seeds are incredibly tiny, and the seedlings grow slowly, which can be a challenge with our overcast spring days. If you're up for it, though, starting seeds indoors in early to late March, about 10 weeks before you plan to transplant, gives them a head start.

Use seed trays with a good seed-starting mix and provide consistent warmth and light. Bottom watering can help prevent damping off, which can be a problem with seedlings in our cool, wet springs. Just set the tray in a shallow container of water and let the soil absorb it from the bottom.

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

Space them about 4-6 inches apart. Keep an eye on the weather forecast – a late cold snap can still happen. Given the small size of Lobelia transplants, you might consider using row covers if a cold night is predicted.

Lobelia needs consistent moisture, which can be a bit tricky in our PNW climate. During the dry summer months, you'll need to water regularly to keep them happy. The "finger test" is a good way to gauge moisture levels: stick your finger about 2 inches deep into the soil, and 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 sometimes humid conditions. Signs of underwatering include wilting leaves and a lack of new growth, while overwatering can lead to yellowing leaves and root rot. Mulching around your plants with compost or bark chips helps retain moisture and suppress weeds.

Lobelia requires minimal pruning, but a little attention will keep them blooming beautifully. 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 down in the fall.

Just use sharp scissors or pruning shears to trim back the stems, leaving some foliage for regrowth. As the first frost approaches in early October, there's no need to prune further. You can simply leave the plants in place until spring, or remove them and compost them.

Lobelia is grown for its ornamental value, not for harvest. You can expect the first blooms in late July through mid-September, about 65 days after planting. The masses of tiny blue flowers are the main attraction, providing a beautiful display in your garden.

Simply enjoy the flowers as they bloom. There's no need to "harvest" them in the traditional sense. Deadheading (removing spent flowers) can encourage more blooms, but it's not essential. As the season winds down and the first frost approaches in early October, you can simply let the plants fade naturally.

Here are a few common problems you might encounter with Lobelia in the Pacific Northwest:

Dies Back in Extreme Heat

• What it looks like: Wilting, browning, and eventual dieback of foliage, especially during hot spells.
• What causes it: Lobelia prefers cooler temperatures and struggles in the rare periods of extreme heat we sometimes get.
• How to fix/prevent it: Provide afternoon shade, especially during the hottest part of the day. Water deeply and regularly. Mulch around the plants to help retain moisture and keep the soil cool.

Damping Off from Overwatering

• What it looks like: Seedlings suddenly collapse and die, often with a fuzzy white or gray mold at the base of the stem.
• What causes it: Overwatering creates a damp environment that encourages fungal growth, especially during our wet springs.
• How to fix/prevent it: Use a well-draining seed-starting mix. Water from the bottom to avoid wetting the foliage. Provide good air circulation.

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 humidity actually benefit Lobelia, but the dry-summer rainfall means you'll need to be diligent about watering during those months. Be especially vigilant about slugs, which thrive in our moist conditions.

Lobelia makes a great companion plant for several vegetables in the Pacific Northwest. Planting them near tomatoes and peppers can attract pollinators, leading to better fruit set. They also work well alongside lettuce, providing a splash of color and attracting beneficial insects that can help control pests.

Avoid planting them near aggressive plants that might shade them out or compete for resources. Lobelia prefers full sun to part shade, so make sure they get enough light.