A native Wisconsin wildflower, Great Blue Lobelia (Lobelia siphilitica) blooms in late summer with bright blue flowers on tall spikes that attract hummingbirds and butterflies. Sometimes a short-lived perennial, Great Blue Lobelia can self-seed under the right conditions, forming attractive colonies in woodland gardens and rain gardens. Provide moist soil, rich in organic matter, to see this plant thrive. May also be known as Great Lobelia or Blue Cardinal Flower.
Use Great Blue Lobelia in shade perennial beds, in the middle to back of mixed borders, and in naturalized woodland areas. This plant is suitable for rain gardens, wet meadows, and along streams or ponds.
Great Blue Lobelia attracts desirable species, such as hummingbirds and butterflies, to your yard. Most mammals will avoid nibbling on this plant, as it contains unpleasant-tasting compounds, making it deer-resistant.
Site Great Blue Lobelia in a moist area in part-shade. The plant can tolerate full sun but will require mulching and consistent moisture to ensure the roots stay cool. Amend soil with compost when planting and add organic mulch (shredded bark or leaves) periodically to increase organic material content in the soil.
It is a fairly low maintenance. Plants may be divided every 3-5 years but it can be short-lived. Cut back flower stalks in late fall if desired and watch for seedlings in spring if spreading is a concern.
It has no major disease or insect issues. Slugs may periodically eat the leaves but prefer Hostas and other plants over this one. Mammals, including deer and rabbits, will generally avoid eating it as well.
Lobelias contain an alkaloid called lobeline, which discourages animals from feeding on it. Lobeline is toxic to humans, so be mindful when siting it around children and pets.
It can be a short-lived perennial, lasting only a few years. However, proper mulching and moisture can help prolong its lifespan, and the plant can self-seed if conditions are right.
Native Lobelias, including Great Blue Lobelia, were once sometimes called vomitwort due to its use in Native American medicine for its cathartic properties. The specific epithet siphilitica is named for its one-time use as a treatment for syphilis.
Pair Great Blue Lobelia with other shade-tolerant plants, such as Astilbes and Lungworts, or with rain garden plants such as Swamp Milkweed or Wild Bergamot (Bee Balm). Cardinal Flower, another member of the Lobelia genus, also pairs well with this plant and provides a nice contrast with its bright red flowers.