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Wisconsin Plant of the Week

Lobelia siphilitica (L.)

Lobeliaceae (Lobelia Family)

Common Name:

great blue Lobelia

09/06/1999

Great blue lobelia is a perennial native herb with fibrous roots, to 1.5 m tall.  It's found on stream banks and lake shores, in wet meadows and swamps.  Like all Lobelias the plants have milky sap, a single stem, and the flowers are 2-lipped -- the "upper" lip has 2 lobes, the "lower" lip has 3.

Leaves are simple and alternate, broadly lance-shaped, wider past the middle, with pointed tips. They decrease in size going up the stem.  The flowers, leaves and stem all have some coarse hairs.

The blue flowers form in the axil of each leaf and are 2 to 3 cm long with white stripes on the "lower" lip.  They bloom through August and September.

Pollination in the lobelias, like in the composites, favors out crossing.  The 5 anthers are attached to form a tube into which the pollen is shed.  The style pushes the pollen out as it grows up through the anther tube. But the receptive surface of the style is only exposed once it's through the anther tube so that any pollen it receives will be from another flower.

  • Origin of the Name: Lobelia, for M. de l'Obel, herbalist to James I (1538-1616); siphilitica, L., of syphilis, used (unsuccessfully) to treat the disease
  • Range:  ME to Man., s. to NC, TX
  • WI Range:  Statewide
  • Common associates:  Marsh milkweed, Joe-pye weed, Swamp goldenrod
  • Wetland Indicator Status: FACW+
  • Coefficient of Conservatism: C = 6 (S&W), C = 4 (MI))
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