Perennial lobelia is our September plant of the month for 2024. These native perennials are some of my favorite flowering plants for the wetland or bog garden. They also make great rain garden plants. Here in the Central Great Plains, there are 4 native species of lobelia, 2 of which can be successfully grown in a garden setting. The other 2 are more wild, but could be planted into a prairie restoration, meadow garden, or glade. And actually, Indian tobacco, Lobelia inflata, is an annual in a glade.
There are around 26 species of Lobelia native to North America, some are short lived perennials and some are annuals. Every state in the lower 48 has at least one species native to it. And many have more. Of the 4 native species in the Central Great Plains, 1 is red flowering, 1 blue, and 2 are white or pale pink. The two that make the best garden plants bloom primarily in August and September.
Lobelias are members of the Bellflower Family along with garden and wild bellflowers, looking-glasses (Triodanis species), and American bellflower (Campanulastrum). The lobelias have a latex compound in their foliage and stems making them poisonous to various mammals. This makes them a good choice for rabbit or deer prone areas.
Cardinal Flower – Lobelia cardinalis
This is one of the best red flowers you can add to the garden. I like to put it in rain garden, bog gardens, or along a dry streambed that fills when it rains. Cardinal flower is a short lived perennial, at least in a place where dryness occurs frequently. I have seen many beautiful specimens however. And there are some great new cultivars with different colors. Cardinal flower grows 1 to 2 feet tall and 1 foot wide.
Red is the primary color, but the Starship Series from Kieft Seed have a variety of colors. The varieties include ‘Rose’, ‘Blue’, ‘Scarlet’, ‘Deep Rose’, and ‘Scarlet Bronze Leaf’. Actually, they are not all cardinal flower species, but hybrids and selections. They can mostly be propagated by seed however. Cardinal flower likes it wet though. I have observed it growing in Kansas alongside ferns in a canyon and under the steady flow of a windmill pump.
Great Blue Lobelia – Lobelia silphilitica
When I first found this growing in a ditch in Northeast Kansas 10 years ago I was so surprised! At the time, I had no idea of the plant at all. But now, I have been using it in my own gardens as well as others. Great blue lobelia is longer lived than cardinal flower, though I would not call either long lived. It grows 1 to 3 feet tall and 2 feet wide. It will grow in standing water as well as in the garden. But it prefers a wet spot. One of my clients has a wet spot in her garden where water pools after a rain or after the irrigation runs. I planted great blue lobelia, cardinal flower, Culver’s root, and Siberian iris in that spot.
Pale Spike Lobelia – Lobelia spicata
This is the one that would be better off in the meadow or prairie garden. In a true prairie remnant, you might find some very large specimens, growing 1 to 3 feet tall. What is a prairie remnant? A prairie remnant is a piece of land with native prairie that has never been plowed or tilled. Near me in Northeast Kansas, there are several small prairie remnants where you can find things like pale spike lobelia, downy gentian, and yellow star grass. Pale spike is a very pale blue or pink, almost white in color. It is rather pretty, but it blooms in spring, opposite of the above 2 flowers.
Pollinators and Pests
The only moth I could find that feeds on lobelias was the pink washed looper moth. But there may be others. I would not be surprised to find 5 to 10 different moths that utilize the latex in the leaves as a defense against predatory insects. Who knows? Lobelias in nature have few problems, but in the garden they may be susceptible to a variety of diseases including Septoria and crown rot. In fact, crown rot may be why they do not live very long in the garden.
Pollinators of lobelias include hummingbirds, long-tongued bees, skippers, and large butterflies like the eastern tiger swallowtail, black swallowtail, and pipevine swallowtail.
Companion Plants
In the garden, specifically the rain garden or bog garden, there are many plants which make good companions of lobelia. Of course, you want plants which can also handle similar conditions. I am planning a bog garden for my front yard, in an area where water collect after a rain. Since I live on a hill, anytime it rains more than .5 inches, I get some standing water.
- Culver’s Root
- Siberian Iris
- Louisiana iris
- Copper iris
- Obedient plant
- Swamp milkweed
- Rose turtlehead
- Joe pye weed
- Rose Mallow
- Side-flower skullcap
- Helen’s flower
- Cup plant
- Giant goldenrod
Conclusion
Lobelias are great plants for the bog garden, rain garden, or wet meadow. With striking colors, they are a great addition for those seeking to attract hummingbirds to the garden. I love having both cardinal flower and great blue lobelia in my garden and seeing what butterflies and hummingbirds come to call. And I hope you will add these flowers to your garden too.
Happy planting!
