August Native Plant Spotlight: Great Blue Lobelia

Happy August! Our native plant spotlight for this month is Great Blue Lobelia, or Lobelia siphilitica, and is one of six species of Lobelia native to Ohio. This perennial belongs to the Bellflower Family, showcasing beautiful blue/purple flowers in August and September. Typically, they grow between 1-5 feet tall, with each flower size around 1 inch long. The flower has a tubelike structure with a 2 lobed upper lip and a 3 lobed bottom lip. Their stems have many simple, alternately arranged leaves which can display both toothed and untoothed leaf margins. The leaves are oval shaped and are often 3-5 inches in length. The stems, sepals, and flowers are slightly hairy. The plant has a raceme structure, meaning there is one main stem with smaller flower stalks clustered off that central stem. This structure type displays indeterminant growth, where it can keep growing given that no environmental limitations are present. The oldest flowers are found at the bottom of the structure, with the newer ones at the top where the new growth is occurring.

Great Blue Lobelia flower raceme structure. Photo courtesy of James L. Reveal, Lady Bird Johnson Wildflower Center.

Great Blue Lobelia’s are found in areas with moist soils such as streams, ponds, floodplains, lakes, or lowland meadows and woodlands. They thrive in full to partial sun but can also tolerate shaded areas. They also do well in a variety of soil types, given that they are moist and well-drained, and can tolerate occasionally wet soil. This species is great for late season blooms and can be planted in a variety of settings, including wetlands, rain gardens, pollinator gardens, riparian areas, etc.

They are great for attracting hummingbirds, butterflies, bees, and other insects. This species is a deterrent to deer and rabbits since it contains a toxic alkaloid compound known as lobeline. If you want to plant this species in your garden, ensure it is not readily accessible to your pets, as the toxic compound can have negative side effects if eaten in large quantities. These hardy perennials also work well as a fast-establishing replacement species for invasive Purple Loosestrife removals. They function very similarly both ecologically and aesthetically. Purple Loosestrife is listed as an aggressive invasive species in Ohio and crowds out natives in wet habitats such as streams, lakes, wetlands, ponds, etc.

Great Blue Lobelia (L) vs invasive Purple Loosestrife (R). Photos Courtesy of gardenia.net (L) and University of Delaware (R).

Fall is a great time to harvest Great Blue Lobelia seeds. Flower heads that are ripe are brown and brittle. The older flowers are lower down the stem and may be riper than the flowers towards the top of the stem. You can cut the seed heads off and let them dry out for easy removal later. Once dried, you can rub or shake the seed head to allow the seeds to fall off. You can either plant them outside in the fall and let them germinate over winter or start them indoors in late winter/early spring, ensuring they receive direct sunlight. They will not successfully germinate without direct sunlight and moist soil. Gently work the seeds into the soil, about 1/8-1/4 inches deep. Great Blue Lobelia’s are great at self-sowing; naturally dropping many seeds on the ground in fall, which makes them a great low maintenance species that’ll spread throughout your garden!

Stay tuned for our September native plant spotlight! For more information on planting natives, visit https://www.butlerswcd.org/pollinators.