great blue lobelia Interesting Notes

The spikes of brilliant true blue flowers on this wetland native attract butterflies, hummingbirds and neighbors to your garden! Lobelia siphilitica provides outstanding color for the border, wet meadow or pond edge. Great blue lobelia naturalizes easily in moist soils, but tolerates periods of drought better than Lobelia cardinalis. Growing 2’-3’ tall and 1’-2’ wide, L. siphilitica blooms at the same time as L. cardinalis and attracts similar insects. The blue coloring is unusual and is especially striking as it comes into season at the same time as yellow asters are in full bloom nearby.

Found in swamps and wet ground from Maine to Manitoba and Colorado, south to North Carolina and Texas, great blue lobelia prefers moist, open spaces in filtered shade. It can tolerate deep shade in drier conditions or full sun and consistently moist conditions. If in a happy situation, plants will self-sow.

Lobelia siphilitica earns its unfortunate specific epithet because it was believed to help with the disease, syphilis. It provides nectar to some species of bumblebees as well as hummingbirds but its seed is believed to be too small to be of much use to most vertebrates, including birds and voles. The great blue lobelia does well in contrast to yellow flowered asters and in moist sites in the perennial border, wildlife garden, restoration area, and in a woodland garden.

Lobelia siphilitica Growing and Maintenance Tips

Lobelia prefers moist, organically rich soil in shady to sunny areas. Tolerates drier locations than L. cardinalis, but insists on some afternoon shade in warmer zones. May self seed if happy. Infrequently, flowers are white. 

Good Substitutions

Lobelia cardinalis 'Black Truffle'

Lobelia cardinalis