Blue Lobelia

Blue Lobelia – Vibrant Blooms for Wet Gardens

The Blue Lobelia flowers in late summer to mid-autumn by producing a raceme of adorable, blueish, two-lipped flowers. The inflorescence rises tall above its finely toothed, wavey-edged foliage that persists along a rigid stalk. They can reach heights of 2-3 ft tall and form clumps that eventually spread throughout the growing area.

Their flowers are long lasting. With their emergence in late summer and early fall, they are not only an important food source for pollinators, but they provide a floral display long after the spring time flowering perennials have died back, rounding out the season for your garden.

Plant Details – Lobelia siphilitica (Blue Lobelia)

Family: Campanulaceae

Hardiness Zones: 4 to 9

Light Requirement: Full sun to partial shade

Water Needs: High

Height: 2 to 4 ft

Spread: 1 to 1.5 ft

Growth Rate: Moderate

Bloom Time: Mid-summer to early fall

Flower Color: Light to dark blue

Wildlife Value: Attractive to pollinators

This delightful perennial is native to Eastern North America and grows in meadows or low wooded areas. They naturally grow in areas with consistently wet soil such as springs, streams and swamps. In the garden, these water loving plants are ideal in moist locations of the yard that receive a little bit of afternoon shade. 

The Blue Lobelia is known for its medicinal properties. Native Americans used this plant to treat nose bleed, cough and headache. It was even used to treat symptoms of syphilis, from which it was given its Latin name of “siphilitica”.

Garden Uses & Growing Tips for Blue Lobelia

These perennials are pest and disease-free, deer resistant, and easy to grow, requiring little to no maintenance. They prefer moist to wet soils with rich humus. To encourage more flower production, deadhead this plant once the flower spike is finished. 

To make the plant more compact, trim back the plant after flowering. This plant also appreciates a light mulch in autumn. Plant these charming perennials in areas of full sun that receive some afternoon shade, however they will grow quite well in part shaded. It loves to have its feet wet and can grow in water as a semi-aquatic plant. Consider planting in a rain garden or boarding a stream or pond.

Why Gardeners Love Blue Lobelia Plants

Late summer – autumn flowering, attractive to pollinators, grows well in wet soil.

With its tall flowering stalk, and clump forming growth habit, this perennial will add unique layers of unique texture and vibrant color to your garden to keep you looking forward to their late summer flowering season. Shop for Blue Lobelia plants online at TN Nursery. For 68 years, we have served the landscaping industry and homeowners with specimen plants.

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How to Grow and Care for Bare Root Perennials, Tubers, and Bulbs

Bare root perennials, tubers, and bulbs are an easy and economical way to jumpstart your garden with lasting beauty. These dormant plants should be planted in early spring or fall while the soil is cool and workable. Before planting, soak bare roots in water for 1–2 hours to rehydrate them. Choose a location based on the plant’s light needs—most flowering types prefer full sun, while others thrive in partial shade.

For bare root perennials, dig a shallow hole and spread the roots out naturally, ensuring the crown is level with the soil surface. For tubers and bulbs, plant with the pointed side facing up at a depth about two to three times their height. Cover with soil, gently press down, and water thoroughly.

Keep soil consistently moist (not soggy) until new growth appears. Add mulch to retain moisture and suppress weeds, but avoid covering the crown or bulb tops. Once established, these plants require little maintenance—just seasonal watering, occasional dividing, and deadheading or pruning as needed. With proper care, they’ll return and thrive year after year.

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