Lobelia in Zone 4A — Mountain West

Lobelia is a gem for Mountain West gardens, offering a vibrant splash of blue that complements our intense sunlight beautifully. The cool nights we experience even in summer enhance the flower color, making them a standout in any border or container. Plus, they attract beneficial pollinators to your garden.

While high altitude gardening in Zone 4A comes with challenges – intense UV, alkaline soil, and a short 118-day growing season – starting Lobelia at the right time allows you to enjoy their blooms from midsummer well into fall. With a little planning, you can easily overcome these obstacles.

Starting Lobelia from seed indoors is possible, but be warned: the seeds are tiny and the seedlings grow very slowly. Honestly, buying starts from a local nursery is often the best bet. However, if you're up for the challenge, start your seeds indoors from mid-March through early April, about 10 weeks before you plan to transplant.

Use seed trays with a good seed-starting mix. Keep the soil consistently moist by bottom watering. Provide supplemental light, as our late spring weather can be unpredictable and natural light might be insufficient. A heat mat can also help with germination.

Transplant your Lobelia outdoors from early to late June, once the risk of frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the intense sun and cool nights common in our region.

Space plants 4-6 inches apart in a location with full sun to part shade. Be gentle when transplanting, as the seedlings are delicate. Keep an eye out for late frosts, which can still occur even in June at higher elevations.

In our dry Mountain climate, consistent watering is crucial for Lobelia. While they need moderate moisture, they are not drought-tolerant and will quickly suffer without enough water. Aim to keep the soil consistently moist, but not soggy.

During the peak of summer, when temperatures reach around 85°F, check the soil moisture daily. Stick your finger about two inches deep into the soil; if it feels dry, it's time to water. Generally, give them about an inch of water per week, either through rainfall or supplemental watering. Water at the base of the plants to avoid wetting the foliage, which can lead to fungal issues in our low-humidity environment.

Signs of underwatering include wilting leaves and dry, crispy edges. Overwatering can cause yellowing leaves and potential root rot. Adding a layer of mulch around your plants helps retain moisture and regulate soil temperature, which is especially beneficial during hot summer days.

Lobelia requires minimal pruning, but a little maintenance goes a long way. When flowering slows down in midsummer, typically around late July or early August, shear the plants back by about half.

This encourages fresh growth and a new flush of flowers as the weather cools down in late summer and early fall. Don't be afraid to cut them back; they're resilient and will rebound quickly. As the first frost approaches around mid-September, you can leave the plants as they are. They'll likely die back with the cold, but you can collect seeds if you wish.

Lobelia is primarily grown for its beautiful blooms rather than a traditional harvest. Expect the first flush of flowers from early August through mid-September, about 65 days after planting.

Enjoy the masses of tiny blue flowers in your garden. To encourage continuous blooming, deadhead spent flowers regularly. Simply pinch or snip off the faded blooms to prevent the plant from setting seed and redirect its energy into producing more flowers.

As the first frost approaches in mid-September, there's no need to harvest anything specific. The plants will naturally decline with the cold weather. You can collect seeds from dried flower heads if you want to save them for next year, but be aware that they may not come true to type.

Here are the top three problems you might encounter growing Lobelia in our Mountain West gardens:

Dies Back in Extreme Heat

• What it looks like: The plant wilts, leaves turn brown and crispy, and flowering stops.
• What causes it: Intense sun combined with high temperatures stresses the plant, especially at high altitude.
• 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 mold around the base.
• What causes it: Overly wet soil and poor air circulation create ideal conditions for fungal diseases.
• How to fix/prevent it: Use a well-draining seed-starting mix. Water seedlings from the bottom to avoid wetting the foliage. Ensure good air circulation and avoid overcrowding.

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 moderate-at-altitude heat, combined with low humidity and dry rainfall, means that consistent watering and protection from intense afternoon sun are crucial for keeping Lobelia healthy and thriving. The alkaline soil can also be a factor, so consider amending your soil with compost to improve drainage and nutrient availability.

Lobelia thrives alongside companions that appreciate similar conditions. Tomatoes and peppers make excellent companions because they provide some shade, protecting Lobelia from the intense UV radiation common in our Mountain gardens.

Lettuce also benefits from the shade provided by Lobelia, as it helps prevent bolting in the heat. Avoid planting Lobelia near aggressive spreaders that might compete for resources, especially water, which is precious in our dry climate.