The Case of the Mistakenly Labeled Lobelias

I love Cardinal Flowers (Lobelia cardinalis), but they don’t love me. Which is to say, they always die on me after a couple of years. They’re fairly finicky. They like lots of sun, lots of moisture, and bed sheets with a thread count of at least 1,800.




But that color! Plus hummingbirds love them – in fact, they are one of few North American plants actually pollinated by hummingbirds – and you can never do enough for hummingbirds.

And Judy missed them, too.

DSC_0139So finally I said to myself, what the heck. I’ll just buy some, and if they die, I’ll replace them. They don’t cost much more than annuals bought as plants.

So I bought a bunch. I planted them in front of our south-facing back porch, near a drainpipe. I also put some in containers.

DSC_0133However, when my Lobelias started to bloom, it became apparent that only one of them was actually a Cardinal Flower. All the rest of them were Great Blue Lobelias (Lobelia syphillitica).

Great Blue Lobelias are very nice plants. They’re not as finicky Cardinal Flowers. But I wanted Cardinal Flowers.

DSC_0134I considered returning them to the garden center where I had bought them. However, I couldn’t remember where I’d bought them – it was one of the two garden centers where I make almost all my (offline) plant purchases, but which one? And of course I hadn’t remembered to keep the receipt.

So I guess I have decided to make the best of having a bunch of Great Blue Lobelias, with occasional outbursts of pointless grumbling.

On a sort of related point: both L. cardinalis and L. siphilitica are native to the American Midwest. However, I think most of the Lobelias sold in garden centers are hybrid cultivars. It turns out this is one instance where the straight species really are a much better choice for pollinators.

7-22 Cardinal Flowers 2
Cardinal flower

As I mentioned before, L. cardinalis is pollinated by hummingbirds. It has evolved to provide a large quantity of nectar to meet the high energy needs of its pollinator.

L. siphilitica is pollinated by bumblebees. They need a lot less nectar, and so L. siphilitica provides a great deal less than Cardinal Flower.

Lobelia cultivars are often L. x intermedia hybrids. They attract hummingbirds with a shape and color that is similar to Cardinal Flower. However, because of their L. siphilitica parentage, they do not offer the same reward in food energy, which is kind of a dirty trick on the hummingbirds, who consume calories by the boatload every minute that they’re in the air.

Ruby-Throated Hummingbird with Cigar Plant.

So be kind to hummingbirds: if you can’t plant Cardinal Flower, don’t plant the hybrid Lobelia cultivars.

FUN FACT: Lobelia siphilitica got its specific name because, yes, for some misguided reason it was used to treat syphilis.

That’s all for now.

39 Comments on “The Case of the Mistakenly Labeled Lobelias”

  1. I had to smile when I read your post. On Friday, I bought one L. cardinalis and one L. siphilitica because I loved both colors. After years of frustration with annuals and overrun day lilies and irises, I’m converting to native plants and trying to determine where they grow best in our gardens. I’m trying not to over-purchase until I learn more. It’s been fun so far, the work is rewarding, and I enjoy pulling up a chair and watching the busy bees. We have hummingbirds at our feeder, so I’m hoping they will like the Cardinal flower as well.

  2. The Lobelia cardinalis is a stunning plant and I would love to grow one here. They are however very tasty for litttle slimy creatures! Interesting that they are rich in nectar for hummingbirds. I bet our little hummingbird hawk moths would like them too.

  3. It it so irritating to get a mislabeled plant. Like you I don’t have the right spot for Cardinal flower. I have tried it two or three places here but it is just too dry. Yet I have seen them in very dry places in the wild. They weren’t thick but a few stalwarts. I might have to try them again. The local Native flower people are offering them for $2 each so it would be worth the try.

  4. We are having a great cardinal flower year! Lobelia does wonderfully well in sites that suit it (moist dappled shade), and happily this year, all of our transplants (from a fortuitous self-sowed patch in a vacant “nursery” bed) are in full flower. As Marion wrote, they’re definitely finicky and short-lived in nature, too. We’re hoping that they’ll continue to self-sow…

  5. I don’t have them survive winters here in SE Nebraska. I don’t plant them every year, but did plant one in a tub with a blue lobelia. I don’t remember whether either is a cultivar. They are just now starting to bloom.

    By the way, my 85 year old mom started singing the song about the lonely petunia in the onion patch when I asked if she knew that song. Ever since, it creeps into my mind, especially when I am gardening, and come across one of my wild petunias. 😉

  6. Very interesting. I have two different types of cardinal flowers in the back and front. The variety in the front yard is a wilder variety. The ones in the back – when the plants started to grow this year, I didn’t recognize them because I could swear they had disappeared for a year or two and now are back blooming in full force, in spite of my lack of attention to them. Now all I need are some hummingbird visitors!

  7. I purchased the native variety of cardinal flower last year from the Native Plant Society. Both did well last year, but this year, one is 3 feet tall, and the other is about 8″. What gives? I’m clueless. I do think they’re lovely. My big one hasn’t bloomed yet either. Have watered the shorter one like crazy. I was unaware a Great Blue Lobelia existed. Sorry for your mishap in this regard.

  8. I have never planted Cardinal Flower, although it’s awesome and does indeed attract the hummingbirds. When it’s blooming at the Arboretum, they are a’buzzin’ around it! I did, however, intentionally plant Blue Lobelia, and the rabbits promptly chewed it to the ground. Ack!

  9. My cardinal flower has returned for a second year, bigger and better than last year so of course I’m worried it will promptly die after it flowers. I think they like doing disappointing things.
    I’ve heard the blue lobelia can be a bit of a spreader.

    • I’ve had great success with Lobelia cardinalis. Here’s what I learned. The flowering stalk always dies but at its base you will find rosettes of new plants. Make sure they are not buried under leaves in the winter but instead are exposed to sunlight; you can put a little straw or chopped leaves around the rosettes but they must be exposed. Snowcover seems to be tolerated, however. And bunnies – I’m not sure is they are guilty. In spring, carefully divide the rosettes. In a few years you will have many plants. L. siphilitica will grow between bricks in a patio – they are tougher! Tolerate drier soil and less care altogether.

  10. Gosh, who would have thought they treated syphilis…I do like your blue ones, even if they weren’t the ones you wanted. The red ones are such a vivid colour though, I can see why you wanted those. Mine are a purple colour, very

  11. Always annoying when what you thought you’d bought turns out to be something else, worse when you were being a good gardener and providing for nature. BTW, I love seeing your humming birds, as you know we don’t have them in Europe so they are very special!

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