• Lobelia siphilitica - Great Lobelia


    "Great Blue Lobelia is a herbaceous perennial that may grow 3 to 4 feet tall. The leaves are alternate with a toothed margin. Blue flowers first mature in mid-summer and continue into early fall. The flowers are larger than other Lobelias and have stripes on the tube portion.

    "This plant provides late summer bloom to the perennial border, wild garden, native plant garden, woodland garden, or naturalized planting. It is also effective near ponds or streams." (North Carolina Extension) 

    Lobelia Siphilitica Botany by Dr. John Hilty

    Bellflower family (Campanulaceae)


    "The preference is wet to moist soil and partial sun. Full sun is tolerated if the soil is consistently moist, and light shade is also acceptable. The soil should be fertile and loamy. This plant withstands occasional flooding, but it will become muddy and ragged-looking if it receives too much abuse. The small seeds require light to germinate. Great Blue Lobelia can be highly variable in height, depending on environmental conditions and its stage of development." (Hilty)

    Faunal Associations: 

    "The nectar and pollen of the flowers attract primarily bumblebees and other long-tongued bees (Anthophora spp., Melissodes spp., Svastra spp.). Less common visitors include the Ruby-Throated Hummingbird, large butterflies, and Halictid bees. The Halictid bees collect pollen only and they are non-pollinating. The caterpillars of a moth, Enigmogramma basigera (Pink-washed Looper Moth), feed on the foliage of Great Blue Lobelia (Schweitzer & Roberts, 2007). Most mammalian herbivores don't eat this plant because the foliage contains several toxic alkaloids, chief among them being lobeline and lobelanine. These toxic substances produce symptoms that resemble nicotine poisoning. However, it has been reported that deer occasionally eat this plant, perhaps enjoying greater immunity to these toxic substances than other animals. The seeds are too small to be of much value to birds." (Hilty)


    1. "Great Blue Lobelia (Lobelia siphilitica)" by acryptozoo is licensed under CC BY-SA 2.0
    2. "Lobelia siphilitica, flower. C & O Canal Park, Montgomery co., MD. (8/15/12)" by FritzFlohrReynolds is licensed under CC PDM 1.0
    North Carolina Extension plant description: Lobelia Siphilitica (Blue Cardinal Flower, Great Blue Lobelia, Great Lobelia) | North Carolina Extension Gardener Plant Toolbox. https://plants.ces.ncsu.edu/plants/lobelia-siphilitica/. Accessed 3 Feb. 2022.

    John Hilty botany, cultivation, and faunal associations:  John Hilty, "Great Blue Lobelia", Illinois Wildflowers, the publisher, Copyright 2004-2019. Accessed 3 February 2022

    Close-up of Lobelia flower image: "Lobelia siphilitica, Great Blue Lobelia, Howard County, MD_2017-09-13-16.57" by Sam Droege is licensed under CC PDM 1.0

    Bee pollinating Lobelia siphilitica: "Bee visiting blue cardinal flower Lobelia siphilitica" by karen_hine is licensed under CC BY 2.0

    Type: Herbaceous perennial
    Family: Campanulaceae
    Native Range: Eastern North America
    Zone: 4 to 9
    Height: 2.00 to 3.00 feet
    Spread: 1.00 to 1.50 feet
    Bloom Time: July to September
    Bloom Description: Blue
    Sun: Full sun to part shade
    Water: Medium to wet
    Maintenance: Low
    Suggested Use: Naturalize, Rain Garden
    Flower: Showy
    Tolerate: Deer, Heavy Shade, Wet Soil

    Information and images compiled by Erik N. Vegeto

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