Cardinal Flower: Keeping it in Your Garden

—This article by Dorothy Swift first appeared in our publication WildfloraRI, Fall 2021

Cardinal flower (Lobelia cardinalis) is a favorite wildflower. But, in order to have it flourish on your own land, you must do some planning before you plant and care for it.

Here are some tips for maintaining cardinal flower in the Rhode Island region, based on my own trial and errors. Some of this experience was acquired since my earlier article about cardinal flower and its ability to attract hummingbirds (Wildflora, Spring 2015).

photo GGardner

Most reference materials state that cardinal flower prefers wet areas in partial shade. This is true for the southern United States. The part about moisture is true for plants that self-seed in the wild, and must compete with other species in order to proliferate. You will commonly find wild cardinal flower in ditches and other moist places. However, in cultivation, I have found that sunny areas with normal good soil and drainage are just fine for plant growth and flowering.

Aim for some clear sky above to provide good light, though there can be some shade from distant trees or dwellings. Plants placed in a shaded area, where bottle gentian thrives, bloomed little and have died off. If it is dry in summer, plants should be watered, along with the other garden plants. They do not need a swamp, bog, ditch or shade to grow well on your own small property.

Another point in reference materials is that cardinal flower is a short-lived perennial. And that is where I made my recent errors. I had observed that my plants increased in the number of flowering stalks and in their height each year for about eight or nine years. I mistakenly thought that they would keep on growing year to year, so I deadheaded plants to avoid too many new seedlings. I figured I had enough plants. However, the following spring of 2020, the cardinal flowers did not re-sprout. And I did not have seedlings coming up, due to deadheading plants the previous year. My hummingbird magnet had disappeared!

Starting from scratch again, I found about four seedlings in the lawn and transplanted them to garden beds. I also bought plants from the August 2020 RIWPS online sale and then some more in June 2021. To maintain these beautiful flowers, I’m going to leave seed on some plants to produce new seedlings. I’ll encourage some self-sown seedlings every year, in order to have a population of plants of various sizes and ages that will persist from year to year.

So, to summarize: full sun is fine, plant in good garden soil and irrigate as needed in summer; leave some seed on plants to produce some new seedlings each year; encourage lots of plants, and be happy when seedlings surprise you in new locations around your garden. Learn to recognize young seedlings, so that you can transplant them to other locations if you wish. In late summer the hummingbirds can’t keep away.