Great Blue Lobelia - Lobelia siphilitica

Phonetic: low-BEE-lee-a sigh-fy-LY-tih-kuh

Great Blue Lobelia provides outstanding, brilliant true-blue flowers for the border, wet meadow, woodland or pond edge. The blue coloring is unusual and is especially striking as it comes into season at the same time as yellow asters. The flower spikes attract butterflies, hummingbirds and neighbors to your garden! If in a happy situation, plants will self-sow.

• Hardiness Zone:  4-9
• Native Region: BONAP Map
• BONAP Map Key Color Guide: Map Color Key
• Sun Exposure:   Full Sun to Part Shade
• Flower Color:  Blue
• Bloom Time:  July, August, September
• Soil Type:  Moist, Wet
• Mature Plant Size:  2-3'H, 1-1.5'W
• Plant Spacing:  1.5-2'
• Host Plant:  
• Attracts:  Bees, Birds, Butterflies, Hummingbirds
• Advantages:  Cut flower, deer resistant, tolerates heavy shade
• Landscape Uses:  Moist perennial border, pond and stream edges, rain garden, woodland garden
• Companion Plants:  Cardinal Flower, Cinnamon Fern, Rose Milkweed, White Turtlehead
• Deer Resistant

Why Great Blue Lobelia is Right for You

Great blue lobelia is good for gardeners working with native perennials who want plants that feel natural and do not need much maintenance. You may be a great match if your garden naturally holds moisture after rain or includes damp, low-lying areas where other plants struggle. This species tends to thrive where the soil stays cool and evenly moist every time.

It’s also a strong fit if you prefer a more naturalistic garden style. Great blue lobelia blends beautifully into rain gardens and pond edges, where plants can self-establish and shift gently over time. Another sign is if you’re trying to support pollinators in a meaningful way. Gardeners who want hummingbirds and other native species to regularly visit their space often find that adding native perennials like this helps create a more active and balanced ecosystem.

What to Expect Throughout the Growing Season

Growing great blue lobelia is a rewarding experience because this native perennial brings something different to the garden in each season.

• Spring: New shoots emerge from the crown once the soil begins to warm. Patience is important as these may grow later than some perennials.
• Summer: Strong stems develop quickly, creating lush foliage before tall flower spikes appear. This is when the plant becomes a busy feeding station for hummingbirds and other native pollinators.
• Fall: As flowering finishes, seed capsules mature and provide food for birds while allowing the plant to naturally reseed in suitable conditions. Leaving the stems in place also adds seasonal interest to the garden.
• Winter: Above-ground growth dies back, but the root system remains alive beneath the soil. Standing stems can offer shelter for beneficial insects until spring cleanup, making your garden more valuable to local ecosystems.

Get high-quality native plants and shrubs from Bagley Pond Perennials today, or contact us for more inquiries.

Frequently Asked Questions

Will great blue lobelia survive in average garden soil?

It can grow in regular garden soil as long as it stays moist, but it does much better in naturally wet, meadow-like conditions.

Does this plant need full sun to grow well?

It grows in full sun to partial shade, but in hotter climates, it often performs better with afternoon shade to prevent stress and maintain consistent blooming.

How fast does great blue lobelia spread in a garden setting?

Great blue lobelia doesn’t spread quickly or take over. Instead, it slowly grows more plants over time by dropping seeds, forming gentle clusters in the garden.

Can I divide great blue lobelia once it is established?

Yes, mature clumps can be divided in early spring, but many gardeners prefer allowing them to self-establish naturally.

What happens if the soil dries out occasionally?

Short dry periods may temporarily lessen flowering and cause drooping, but plants usually recover quickly once moisture levels return to suitable conditions.