Lobelia in Zone 7A — Mountain West

Lobelia is a charming addition to any Mountain West garden, bringing a splash of vibrant blue to your flower beds and containers. The cool nights we experience even in summer enhance the intensity of the blooms, making them a standout feature. Plus, their spreading habit makes them perfect for filling in gaps and softening edges.

Our high altitude and intense sun present some challenges, but with careful timing and attention, you can enjoy a beautiful display of Lobelia. Our 173-day growing season requires starting seeds indoors or buying starts, but the reward is well worth the effort.

Starting Lobelia from seed indoors can be rewarding, though it's often easier to simply buy starts. If you're up for the challenge, begin in mid-February through early March, about 10 weeks before you plan to transplant them outdoors.

Use seed trays with a good seed-starting mix. Keep the soil consistently moist by bottom watering to avoid disturbing the tiny seeds. Provide warmth and plenty of light, especially considering our late spring starts in the Mountain West.

Transplant your Lobelia seedlings outdoors in early May through early June, after the danger of frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This is especially important in the Mountain West, where temperature swings can be dramatic.

Space your Lobelia plants 4-6 inches apart to allow for their spreading growth habit. Given how tiny the seeds are and how slowly they grow, many Mountain gardeners opt to buy established starts from a local nursery.

Lobelia needs consistent moisture, which can be a challenge in our dry Mountain climate. Aim to keep the soil consistently moist, but not waterlogged. They are definitely not drought-tolerant.

During the peak of summer, when temperatures can reach around 85°F, check the soil moisture frequently. Use the "finger test" – stick your finger about 2 inches into the soil. If it feels dry, it's time to water. In general, aim for about 1 inch of water per week, watering at the base of the plants to minimize water loss due to our low humidity and intense sun.

Signs of underwatering include wilting and dry, crispy leaves. Overwatering can lead to yellowing leaves and root rot. A light layer of mulch can help retain moisture and regulate soil temperature, a useful strategy in our climate.

Lobelia requires minimal pruning, which is great for busy Mountain gardeners. The main thing to remember is to shear back the plants by about half when flowering slows down in midsummer. This encourages fresh growth and a new flush of flowers as the weather cools down in the fall.

Use sharp scissors or pruning shears to trim the plants back. Don't be afraid to cut them back quite a bit – they're resilient. As the first frost approaches in early October, you can let the plants fade naturally, as they are unlikely to survive our winters.

Lobelia isn't really a plant you "harvest" in the traditional sense. Instead, you enjoy them as garden flowers, reveling in their masses of tiny blue blossoms from early July through late August. Their peak bloom time coincides with the height of our short but intense Mountain summer.

As the flowers fade, you can deadhead them to encourage continued blooming, but this isn't strictly necessary. Simply enjoy the beauty they bring to your garden. As the first frost approaches in early October, let the plants go to seed, or simply pull them up and add them to your compost pile.

Here are some common problems you might encounter growing Lobelia in the Mountain West:

Dies back in extreme heat

• What it looks like: The plant wilts, leaves turn brown and crispy, and flowering stops.
• What causes it: Lobelia struggles in high heat, especially combined with our intense sun.
• How to fix/prevent it: Provide afternoon shade, especially during the hottest part of the summer. Ensure consistent moisture. If the plant dies back completely, don't give up! It may return when temperatures cool down.

Damping off from overwatering

• What it looks like: Seedlings suddenly collapse and die, often with a fuzzy, moldy growth at the base.
• What causes it: Fungal disease thrives in overly moist conditions, especially when starting seeds indoors.
• How to fix/prevent it: Use a sterile seed-starting mix, ensure good air circulation, and avoid overwatering. Bottom water seedlings to keep the foliage dry.

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.

Mountain West Specific Challenges: Our combination of moderate-at-altitude heat, low humidity, and dry rainfall means Lobelia can be a bit finicky. Consistent watering is key, and providing some afternoon shade can help them thrive.

Lobelia makes a great companion plant in the Mountain West garden. Plant them near tomatoes and peppers, and their delicate flowers attract pollinators that will also benefit your vegetable crops.

They also pair well with lettuce, as their spreading habit can help shade the soil and keep the lettuce roots cool, which is especially helpful during our intense summer sun. Avoid planting them near anything that will aggressively compete for water, as Lobelia prefers consistently moist soil.