Three lobelias . . . three different colors . . . three similar flower shapes . . . and three similar leaves and stems. Here’s a closer view of the top flowering portion of each plant:
Do you recognize any of these wildflowers? The one on the left is commonly referred to as Indian tobacco. Its scientific name is Lobelia inflata. The middle wildflower is Cardinal flower with the scientific name of Lobelia cardinalis. And the right-most plant is Great lobelia whose scientific name is Lobelia siphilitica.
Not only do these plants have a raceme of flowers at the top of each plant, they also develop flowers from their leaf axils.
Let’s look more closely at each lobelia’s flower. See what you notice about how similar they are.
Indian tobacco (Lobelia inflata)
Cardinal flower (Lobelia cardinalis)
Great lobelia (Lobelia siphilitica)
What I notice is that each bilaterally symmetrical flower is “two-lipped” with two lobes in the upper lip and three lobes in the lower lip. They also have a long pistil which curves downward so that the tip is over the opening into the deeper parts of the flower where the nectar resides. The stamens are actually fused to the pistil.
You can see this most clearly in the Indian tobacco image above. Here are two more photos which provide closer views of the flower so you can see the unique pistil these lobelias have.
Cardinal flower (Lobelia cardinalis)
Great lobelia (Lobelia siphilitica)
Now, let’s compare the three plants’ leaves and stems. Look carefully . . .
Each lobelia’s leaf has finely toothed margins. They also have what appear to be small white dots along the margin. As for the stems, they have fine hairs. (I realize you may not be able to see this very well with the Great lobelia photo. Click on the third composite image–up above–to see the downy hairs on the Cardinal flower’s stem.)
This last image provides a good view of the white dots along the leaf margin for Indian tobacco. You can also see its hairy stem.
Indian tobacco (Lobelia inflata)
Thanks for the very interesting and informative information.
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are there look alikes to lobelia. I found a few plants that had a more violet color to the flower, had a similar shaped flower, with long stamen, 5 green spikes surrunding flowers, flower heads were hairy, but stem was mostly smooth. flowers with the 3 lower lobes, and two pointy top petals, but thefowers have whitish strips leading into them. I could have sworn it was lobelia, but now I am completely unsure. The leaves do have white dots on margin which is finely serrated. leaves are alternate and come straight from the stem. it is too wilted now to picture it, but i was hoping you could shed light on this mystery. Is it a variant strain of some sort of lobelia, or is it some type of loo alie, while the flowering tops were hairy the leaves have only a VERY fine hair along leif veins. the stem is very smooth with very few fine tiny hairs. stem is angular, with ridges, instead of a perfect roundness. Please help me with this id. thanks a lot.
You may want to check out this blog post for a comparison with a similar plant: http://identifythatplant.com/two-blooming-blue-or-purple-wildflowers/
And your description of the plant you have does sound like it may be Great lobelia (Lobelia siphilitica). Is it growing in the region where Great lobelia could typically be found? Look for Lobelia siphilitica on the plants.usda.gov website to check on its region.
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