Lobelia siphilitica, Great Blue Lobelia

Great Blue Lobelia has managed to endure in many old pastures in Floyd County and might be spotted as a short purple, blue-purple, or sometimes white flowering spike in late summer, short because it got mowed early in the season. Mostly erect and unbranching, rough lance-shaped leaves ascend the stalk, alternately attached without stems. The smallish purple flowers cluster around the top flower spike, in a spiral pattern around the central stem. By looking up close, one can see that the tubular flowers have three fused petals below and two above which usually curl backward, the opening of the flower pointing outward. They look like a face 🙂


In medium to wet soils in light shade, Lobelia siphilitica can form healthy colonies, but is not overly aggressive. Prairie Nursery says that this plant grows well in damp clay soil. Here in the mountains, it will also survive and flower in dryish shade, as well as in average full sun, though its full glory will not be achieved outside of moist bright shade. Foliage is not overly handsome, but its browning as dormancy sets in after flowering comes late enough that it doesn’t present an eyesore in the garden. This plant tends to survive deer browse due to a compound in the leaves called lobeline. Grows in the same conditions as Lobelia cardinalis (Cardinal Flower). Planted together, the contrasting colors (in this case, red and purple) can be quite stunning and color contrast is said to attract hummingbirds and butterflies. Relatively short-lived, it relies on reseeding to persist in the landscape.


Hummingbirds and butterflies are drawn to the late summer to fall flowers of Lobelias, which will be more attractive when massed with other flowers of contrasting colors. The plant needs pollinators to reproduce and heavier bees such as bumblebees will have the weight needed to press down the bottom petals to enter the flower in search of nectar. Entering and backing out wipes pollen on the bee’s back, which does the job! Some bumblebees chew through the bottom of the flower to short-circuit this process. Despite these shortcircuits to its reproductive strategy, Lobelias continue to survive in Floyd County even under grazing, mowing, and other pressures

Virginia Heritage Communities

Lobelia siphilitica has been found in the following Virginia Heritage Communities (relatively intact ecosystems that have been surveyed and catalogued by the Virginia Department of Conservation and Recreation (DCR): Piedmont / Mountain Small-Stream Alluvial Forests, Calcareous Fens and Spring Marshes, and Rocky Bars and Shores. The following two heritage communities have been surveyed in Floyd County:

  • Central Appalachian Montane Alluvial Forest [USNVC CEGL008405, Liriodendron tulipifera – Pinus strobus – Quercus alba – (Tsuga canadensis) / Carpinus caroliniana Amphicarpaea bracteata Forest (G3/S3)] a type of type of Piedmont / Mountain Small-Stream Alluvial Forest.
  • Central Appalachian Calcareous Shrub Fen / Seep [USNVC: CEGL008408, Alnus serrulata Osmunda spectabilis – Carex tetanica – Carex leptalea Shrubland (G1?/S1)], a type of Calcareous Fens and Spring Marshes at Buffalo Mountain.

**Please do not hike off trail at Buffalo Mountain to try to glimpse these globally rare habitats. They are fragile, protected, and cared for closely by Virginia DCR. Collecting plants or seeds from protected areas is strictly prohibited.**

Human Use

“Native Americans traditionally use this species to treat respiratory and muscle disorders. It was once considered a cure for syphilis by early European settlers, which is where the scientific name for this species originates.” (Wikipedia, 2023) However, all parts of the plant are poisonous when consumed in large quantities. “Symptoms include nausea, vomiting, diarrhea, salivation, exhaustion and weakness, dilation of pupils, convulsions, and coma. Toxic Principle: Alkaloids lobelamine, lobeline, and others, plus a volatile oil.” (Poisonous Plants of N.C. via Wildflower.org)


Scientific Name

Lobelia siphilitica

Other names: Blue Cardinal Flower, Great Lobelia

Family: Campanulaceae (bellflowers).

Native Status

Native to Floyd County

Native Range Map (Virginia Counties) for Lobelia siphilitica

Source: Digital Atlas of the Virginia Flora

Native to eastern and central Canada and the United States.

USDA Lobelia siphlitica range map

Other Floyd County native Lobelia: L. cardinalis, L. inflata, L. spicata, L. spicata var. scaposa.

Culture Notes

Height: 3-5 ft, Spacing guide: 12"-18". Bloom Color: Purple, Blue. Bloom Time: Late Summer/Early Fall (Jul-Sep). Light: Full sun to full shade. Moisture: Semi-dry to moist (submesic to subhydric) conditions. Soils: Well drained sand, loam, clay-loam.


USDA Zones: 4-9. National Wetland Status Indicator: FACW. C-Value: 4. Successional Role: Subclimax, stable.

Virginia Ecology

Virginia Habitat: "Floodplain forests, mesic cove and slope forests, fens, seeps, stream banks and bars, moist clearings, wet meadows, and low roadsides. Common in the mountains; frequent in the Piedmont; infrequent in the Coastal Plain." (The Flora, 2023). Virginia Natural Communities: Rocky Bars and Shores, Calcareous Fens and Spring Marshes, Piedmont / Mountain Small-Stream Alluvial Forests

Ecosystem Services

*Of Special Value to Native Bees, *Of Special Value to Bumblebees, *Of Special Value to Native Butterflies, Supports Conservation Biological Control, Hummingbird Nectar Source

Wildlife Supported: Hummingbirds, butterflies, bees especially bumblebees.


Divide clumps in the spring or scatch cold moist stratified seed lightly onto the soil surface. Seed Germination: C60 - 60 days cold moist stratification required

Where to Buy

Prairie Moon Nursery, Prairie Nursery, locally from Wood Thrush Natives, Mother’s Child Farm, Spikenard Farms Honeybee Sanctuary, other Floyd Farmers Market vendors.