Lobelia adds August color, keeps pollinators happy


Hanging basket lobelia adds vibrant blue to mixed hanging baskets, and it’s photographed primarily in the Northwestern coastal states where the plant blooms from spring until frost.

In the Midwest, however, the hot temperatures and high humidity of summer causes the plant to fall into dormancy and stop flowering. Perennial native lobelia, although unsuited to baskets, gives a better display in area gardens and is good for local wildlife, too.

There are two perennial lobelias that are mainstays of our garden in the August — Great Blue lobelia (Lobelia siphilitica) and Cardinal flower (Lobelia cardinalis). Both are native to the eastern portions of the United States and are found primarily in wetlands and sunny areas adjacent to streams and ponds. But they also do well in garden soil. They carry perennial borders after the flush of early summer blossoms through the arrival of the Japanese anemones and asters announcing autumn is on the way.

Our garden has a lot of Great Blue lobelia because, despite its roots as a wetland plant, it grows almost anywhere. It started out in the bogs of our small ornamental pools. It’s a favorite of the honey bees, small pollinators, butterflies and hummingbirds. It has toothed leaves but a growth habit similar to foxgloves with clumps sending up multiple 2 and 3-foot tall spikes of small light blue flowers.

If I was attentive, I’d cut the spent flowers so the display would go on until frost some years. Of course, I wasn’t always attentive and that’s how I discovered that Great Blue lobelia thrives in part shade and dry soil.

Great Blue lobelia seedlings have shallow root balls so they’re easy to transplant. I weeded out a bucket of them the other day in some disturbed soil. They were easy to pull since the plants were still small. If I had cut the parent plants back in the autumn, I could have saved myself some work.

The little plants take a year to reach blooming size and are short-lived, although they replace themselves with seed. And despite its name, Great Blue lobelia can sometimes produce white flowers.

Cardinal flower has been harder than its cousin to keep in our garden. I used to grow the native in our bog but the tall flower spikes it produced flopped. I needed something shorter, so I looked at hybrids and now plant ‘Ruby Slippers,’ which is about 30 inches tall in bloom.

These are plants that have been produced by cross-breeding Great Blue lobelia, Cardinal flower and a native Mexican lobelia (L. fulgens). Other hybrids come in shades of purple, red and apricot and can be 30 to 40-eight inches tall when flowering. Several like ‘Queen Victoria’ and ‘Black Truffle’ also have dark foliage. The hummingbirds, bees and butterflies have flocked to each one I’ve tried.

There’s another native lobelia, a wildflower with the terrible common name puke weed (L. inflata). This is a biennial with the same type of five-petal flowers as the rest of the lobelias. It was burned by indigenous people to discourage biting insects and as a purgative. Its weedy appearance has limited its use in perennial gardens.


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Wisconsin’s largest paid circulation community weekly newspaper. Serving Port Washington, Saukville, Grafton, Fredonia, Belgium, as well as Ozaukee County government. Locally owned and printed in Port Washington, Wisconsin.

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