Lobelia in Zone 7A — Pacific Northwest

Lobelia is a fantastic addition to any Pacific Northwest garden. The masses of dainty blue flowers are a welcome sight, and they look particularly lovely cascading from containers or softening the edges of garden beds. Plus, the cool nights we often have here seem to enhance the flower color.

While our springs can be a bit slow to warm up and our summers aren't exactly scorching, Lobelia thrives with a little planning. With our 183-day growing season, you’ll have plenty of time to enjoy these beauties.

Starting Lobelia indoors is an option, but honestly, with their tiny seeds and slow early growth, it can be a bit fussy. If you're up for the challenge, start seeds indoors from mid February through early March, about 10 weeks before you'd like to transplant.

Use seed trays with a good seed-starting mix, and provide warmth and bright light – a grow light is really helpful here, especially with our overcast spring days. Bottom watering is key to prevent damping off; set the tray in a shallow dish of water and let the soil soak it up from the bottom.

Given the tiny seeds and slow growth, I usually recommend buying Lobelia starts from a local nursery. It's just easier! If you do start your own, transplant them outdoors from early May through early June, after hardening them off for about a week.

Hardening off involves gradually exposing your seedlings to outdoor conditions. Start with an hour or two in a sheltered spot and increase the time each day. Space them 4-6 inches apart in a location with full sun to part shade. Keep an eye on the weather; those late spring showers can be a bit much for tender seedlings, so protect them if needed.

Consistent moisture is key for Lobelia, especially during our dry summer months. While our summers are mild, that doesn't mean it doesn't dry out! Lobelia isn't drought-tolerant and will quickly go dormant if allowed to dry out.

During the spring, when we're getting plenty of rain, you might not need to water at all, but once those dry summer months hit, check the soil regularly. Use the finger test: stick your finger about 2 inches into the soil. 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. Signs of underwatering include wilting leaves and dry soil. Overwatering can lead to yellowing leaves and potentially root rot. Adding a layer of mulch, like composted leaves or bark chips, can help retain moisture and keep the soil cool.

Lobelia doesn't require a lot of pruning, but a little attention will keep it looking its best. When the flowering slows down in midsummer, shear the plants back by about half.

This might seem drastic, but it encourages fresh growth and a new flush of flowers as the weather cools down in the fall. Don't worry about being too precise; just give them a good trim. As we approach our first frost around mid- October, let the plants be. There's no need to prune them before winter.

Lobelia is primarily grown for its beautiful flowers, so there isn't a traditional "harvest" involved. Instead, enjoy the masses of tiny blue (or white or pink, depending on the variety) flowers as they bloom from early July through late August.

The plants will continue to produce flowers throughout the summer if you keep them watered and shear them back when needed. To encourage continued production, deadhead any spent flowers. As the first frost approaches in mid- October, you can simply let the plants fade naturally. They aren't frost-hardy, so they won't survive the winter.

Here are a few common problems you might encounter with Lobelia 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 we have mild summers, prolonged periods of temperatures rarely above 90°F can still stress Lobelia.
• 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 cool.

Damping Off from Overwatering

• What it looks like: Seedlings suddenly collapse and die, often with a fuzzy gray mold visible.
• What causes it: Overwatering, especially with poor drainage, creates a breeding ground for fungal diseases. Our wet springs can exacerbate this issue.
• How to fix/prevent it: Use a well-draining seed-starting mix. Bottom water seedlings 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 thrive in our moist climate. They hide under mulch and debris during the day and come out at night to feed.
• How to fix/prevent it: Use beer traps (shallow dish of beer sunk into soil). Apply 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 is another option.

Pacific Northwest Specific Challenges: Our mild heat and dry-summer rainfall pattern can be both a blessing and a curse for Lobelia. The mild temperatures generally suit them well, but the dry summers mean you need to stay on top of watering. And of course, the slugs are always a concern!

Lobelia makes a great companion plant for several vegetables in the Pacific Northwest garden. Plant it near tomatoes and peppers. The Lobelia attracts pollinators, which can improve fruit set for these crops.

It also works well near lettuce, acting as a ground cover to help retain moisture and suppress weeds. I wouldn't recommend planting it near anything that requires very dry soil, as Lobelia needs consistent moisture.