Great Design Plant: Lobelia Siphilitica Keeps Its Cool
Great blue lobelia, a flowering native that prefers moist soil, adds a calming blue hue to the late-summer garden
Benjamin Vogt
December 9, 2014
Houzz Contributor. I'm a big advocate for bringing the tallgrass prairie into our urban lives -- only 1% remains, making it more threatened than the Amazon rainforest yet also as effective at sequestering CO2. I own Monarch Gardens LLC, a prairie garden design firm based in Nebraska and working with clients across the Midwest. I also speak nationally on native plants, sustainable design, and landscape ethics while hosting online classes. I'm the author of A New Garden Ethic: Cultivating Defiant Compassion for an Uncertain Future. In the coming years we want to restore a 40+ acre prairie and host an artist residency program.
Houzz Contributor. I'm a big advocate for bringing the tallgrass prairie into our... More
You’re probably quite familiar with red cardinal flower (Lobelia cardinalis), but there’s another version you might not know that’s easier to care for and tends to have a longer perennial lifespan. Great blue lobelia (Lobelia siphilitica), or blue cardinal flower, flowers from late summer to early fall — providing calming violets and blues when summer is at its hottest. You’ll see diverse native bees stopping by, even the occasional moth or butterfly. Planted in drifts and masses, it is a real stunner for the front or middle of the border. Seed in fall or winter for flowers the following year.
Botanical name: Lobelia siphilitica
Common names: Great blue lobelia, blue cardinal flower
Origin: Native from Minnesota southwest into Wyoming and Colorado, south to Oklahoma and Louisiana, and all points east
Where it will grow: Hardy to -40 degrees Fahrenheit (USDA zones 3 to 9; find your zone)
Water requirement: Medium to wet soil
Light requirement: Full sun if wet soil; partial shade if medium soil
Mature size: 2 to 3 feet tall and up to 18 inches wide
Benefits and tolerances: Likes wet soil; tolerates some shade; unique color and form
Seasonal interest: Blooms in midsummer to early fall; some winter interest with mature plants that have multiple spires
When to plant: Potted or bare-root plants can be planted from spring to fall; seed in fall or winter.
Photo: rockerBOO
Common names: Great blue lobelia, blue cardinal flower
Origin: Native from Minnesota southwest into Wyoming and Colorado, south to Oklahoma and Louisiana, and all points east
Where it will grow: Hardy to -40 degrees Fahrenheit (USDA zones 3 to 9; find your zone)
Water requirement: Medium to wet soil
Light requirement: Full sun if wet soil; partial shade if medium soil
Mature size: 2 to 3 feet tall and up to 18 inches wide
Benefits and tolerances: Likes wet soil; tolerates some shade; unique color and form
Seasonal interest: Blooms in midsummer to early fall; some winter interest with mature plants that have multiple spires
When to plant: Potted or bare-root plants can be planted from spring to fall; seed in fall or winter.
Photo: rockerBOO
Distinguishing traits. Great blue lobelia turns on when many gardens are in a late-summer transition phase. Sometimes the blooms appear purple, sometimes bluer. You’ll find a host of long-tongued pollinators, from bees to butterflies and moths, enjoying the nectar. Another benefit? Rabbits and deer tend to leave it alone.
Photo: Aaron Carlson
Photo: Aaron Carlson
How to use it. Preferring a slightly loamy and rich soil, great blue lobelia looks great when massed and paired with other late-summer bloomers. Perfect at the water’s edge but not in a mucky location, this midsize plant will provide some vertical interest.
Planting notes. In its southern range, great blue lobelia appreciates consistent moisture or partial shade. It will self-sow only in optimal conditions. The seeds are small and need light to germinate, so a thickly planted garden will keep any unwanted seedlings at bay.
Photo: rockerBOO
More:
See more Houzz guides to beautiful blue flowers
Browse plants native to other regions of the U.S.
Planting notes. In its southern range, great blue lobelia appreciates consistent moisture or partial shade. It will self-sow only in optimal conditions. The seeds are small and need light to germinate, so a thickly planted garden will keep any unwanted seedlings at bay.
Photo: rockerBOO
More:
See more Houzz guides to beautiful blue flowers
Browse plants native to other regions of the U.S.
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Wow what a gorgeous flower. I really would like to grow some. Love the colour.
We live in the Hudson Valley of NY, and these do self-seed easily in our yard. I usually find about a half dozen seedlings each spring. This year after a wet fall and very wet spring, I counted 30 to 40 seedlings! popping up everywhere, even into the grass. But easy to remove or transplant if watered in well after moving.