Great Blue vs. the weevil

By Alexandra Ratliff

Alexandra Ratliff is a recent graduate of Chatham University with a B.S. in Environmental Science.  She is a Restoration Management Assistant at Kankakee Sands. After conducting research on Lobelia species, Alexandra has found herself madly passionate about the Great Blue Lobelia.

When I first arrived at Kankakee Sands, I was overwhelmed by the diversity of plants that I encountered daily. There were so many different shapes and colors to soak up. Having done previous research on Great Blue Lobelia (Lobelia siphilitica) in college, I was especially excited to see it blooming here.  I spotted my first Great Blue in mid-August. Its beautiful blue hues burst out from the surrounding shades of golden brown and dark green.

Great Blue Lobelia is a perennial native plant that tends to grow in low woodlands and wetlands. It can grow up to three feet tall and has brilliant blue flowers and rounded dark green alternating leaves. It blooms in late July through September, sets seed in early to mid-October and overwinters as rosettes (circular set of leaves located close to the soil).

The Great Blue has more going for it than just its striking blooms. Beneath its vibrant exterior is an intricate system of tubular structures that contain chemical compounds called alkaloids. These alkaloids have a bitter taste and may act as a defensive tool. When a Lobelia leaf or flower is damaged, alkaloids are released at the site of damage.

You may be wondering why the Great Blue needs this defense tool. If you look closely at a Great Blue, sometimes you can see small black critters crawling around on the leaves and flowers. These critters are called weevils. Feeding on the seeds of the Great Blue, the weevils can also damage its leaves and flowers. When the weevils bite into a Great Blue, the plant already has a defense mechanism in place. The bitter alkaloids are released, protecting the plant from further harm.

There are still many mysteries out on the prairie, and we continue to examine the complex relationships in order to better understand our world. Next time you are out in the prairie, look for the blue flowers of the Great Blue Lobelia. You may find yourself becoming a fanatic of the flower, too.

The Nature Conservancy’s Kankakee Sands of Indiana and Illinois is 10,000 acres of prairie and savanna habitat in Northwest Indiana and Northeast Illinois, open every day of the year for public enjoyment.  For more information visit or call the office at 219-285-2184.

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