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What is a Cardinal Flower?

Beautiful flying hummingbird approaching the blossoms of a red cardinal flower

Lobelia Cardinalis

Lobelia cardinalis, otherwise known as the cardinal flower, is a flowering plant that is a member of the bellflower family (campanulaceae). The flower gets its name from the similarity of the flower shape to the red robes worn by Roman Catholic cardinals.

This beautiful plant is cold hardy, is easy to care for, and is not encumbered by pests like rabbits, deer, or aphids. They can exist in almost any hardiness zone and have a very long and prosperous growing season. When other perennial plants are ending their blooming season due to the hot summer heat, the cardinal flower remains.

The cardinal flower is fit for any level of gardener expertise, and we will go into plenty of detail in this article on growing cardinal flower plants in your garden, balcony, greenhouse, or front window. If in the end you decide it’s not precisely what you’re looking for, head on over to our list of Wonderful Flowering Plants from all over the globe where you’ll surely find the perfect fit for your green space.

Related: Types of Red Flowers | Types of Flowers | Types of Flowers by Color | Types of Flowers by Alphabet | Types of Flower Colors

Small cluster of young red cardinal flowers blooming against a blurry green background

What do Cardinal Flower Plants Look Like?

Growth Pattern

Cardinal flowers are borne in clusters at the ends of leafy stems. Each stem is lined with dark green foliage. This plant has an upright climbing growth habit, which each stalk rising from a basal rosette of leaves. They can grow to be up to 2 metres tall and 18 inches wide.

Leaves

Cardinal flower leaves are alternately arranged along stems and are about 2 inches in length. Each leaf is a dark green color and is lanceolate in shape.

Flowers

This plant produces very showy red flowers that blooms starting in early spring – usually May – and can persist all the way through until late summer – usually October. Flowers are borne in densely packed terminal spikes.

Each individual flower spike is about 8 inches in length. Flowers are two lipped, with 2 upper erect petals and 3 lower spreading petals. Each petal meets into one united tube at the base of the bright red flower.

These long tubular flowers introduce a certain amount of difficulty for smaller pollinators when it comes to harvesting nectar, but that is not the case for hummingbirds. Bees, wasps, and moths tend to avoid cardinal flowers, leaving tons of sweet nectar for the ruby throated hummingbird and others.

Tall stalks of cardinal flower plant with blooming red flower spikes growing in a luscious garden

What some Other Cardinal Flower Varieties?

Blue Cardinal Flower (Lobelia Siphilitica)

This variety is the blue counterpart to the common cardinal flower. This is a showy perennial plant that produces tubular lavender colored flowers at the axils of leafy bracts. Each flower is split into 2 lips (much like lobelia cardinalis) with 2 upper petals and 3 lower petals. A lower petal is slightly larger than an upper petal.

This flower actually gets its scientific name because it used to be thought that making blue cardinal flower tea could potentially cure syphilis!

Close up shot of blueish purple cardinal flower blossoms growing in terminal spikes at the end of flower stalks

Sierra Madre Cardinal Flower (Lobelia Laxiflora)

This variety of cardinal is a much larger perennial herb that grow to be a subshrub or full sized shrub. Leaf sizes tend to vary, but inflorescences are borne at the end of a flower stalk as racemes bearing several tubular flowers that are mostly yellow in color. This plant is a wonderful option for creative a wildflower garden.

Curled petals and anthers of a yellow cardinal flower

Where do Cardinal Flowers Grow?

Cardinal flowers are a native plant to the United States, specifically in Illinois, Indiana, Iowa, Michigan, Missouri, Ohio, and Wisconsin. Though they are native to the states, they are capable of growing in USDA growing zones 1 through 10. That is one cold hardy plant!

This plant is a water loving plant, and when growing in the wild it can most likely be found growing in wet areas. Cardinal flowers can be found growing near a wetland or near lakes, swamps, ponds, and stream banks. They grow in open spaces like a wet meadow, prairie, pasture, and plain, and perform very well on roadsides and woodland edges.

Wild red cardinal flowers growing on tall stalks near a wetland

How do you Propagate a Cardinal Flower?

There are many plants that are difficult to propagate, but cardinal flowers are not one of them. They can be propagated by seed, by cutting, or by another method entirely.

Seed Propagation

Seeds can be harvested from cardinal flower seed pods. These are small capsules that slightly open at either end of the capsule. It can be pried open to reveal small black seeds inside.

These cardinal flower seeds can be cleaned and dried in a sealed container in the refrigerator for up to 3 years, or whenever you feel like planting them.

Before seeds are ready for germination, they can be helped by both a 3 month period of cold temperatures, and stratification. Seed stratification is basically irritating the seed by scratching to help trigger germination.

When that time comes, pick a spot in the garden that receives light shade, and in soil that is moist and well drained. Soil can be mixed with organic matter to help with germination.

Plant seeds about 12 inches apart from one another. This should be more than enough space for happy plants. A new plant like to receive a lot of water during this time, and planting them in partial shade helps to keep a moist area.

Stem Propagation

So usually stem propagation means cutting the stems of a healthy plant and keeping them in either a cup of water or in a pot of soil until it takes root again.

Cardinal flowers are nifty because they can take root by the stem of an already established plant being simply bent down and held down by something heavy. The live stem will begin to take rot into the soil and grow around the heavy item, where it can eventually be removed.

Spikes of red cardinal flowers growing from a bush near a green lawn

What are the Growing Conditions of Cardinal Flowers?

Soil Type

The main requirement of soil type for cardinal flowers is that it is consistently moist soil. This is a rare plant in the way that it wants to be as wet as possible.

Soil should be fertilized with plenty of organic matter, and rich soil can be either humus based, medium loam, clay loam, sandy, sandy loam, clay, or limestone based.

Sun Exposure

Cardinal flowers are not particularly picky about their exposure to sun. They can tolerate anything from full sun, to partial shade, to full sun conditions – thought they tend to perform the best with full shade in the morning and partial afternoon shade.

Water Level

It is important that cardinal flowers have consistently moist soil. These plants should be watered excessively when there is not consistent rain.

Temperature

Cardinal flowers are wonderfully cold hardy plants, and can survive in USDA growing zones as low as 1. In colder regions they are thankful to be provided with a layer of heavy mulch to help protect their roots during the winter.

Otherwise, the only temperature requirement is that their seeds have a good 3 months of cold in the spring time before they germinate.

Amazing red cardinal flower in full bloom coated in a layer of frost

Fertilizer

Like most flowering plants, the cardinal flower also responds very well to fertilizer. They can be fertilized either by a general purpose fertilizer in the fall, or the soil they exist in can be incorporated with a shovelful of compost.

Pruning

When it comes to pruning, cardinal flowers can be deadheaded at the end of their blooming season if you do not want them to self seed. If you do want them to self seed, leave them on!

Otherwise, in cooler growing regions, the plants can be cut back in the fall as the cold weather approaches so that they go into dormancy, and will be ready to pop up again the following spring!

Intolerances

Cardinal flowers are known for being a wonderfully low maintenance plant. They’re very cold hardy and don’t have many growing requirements other than having healthy and wet soil. Their main intolerance is that they are intolerant to drought, but that is about it!

Field of red cardinal flowering growing at the tips of stems next to a lazy river and big boulders

How are Cardinal Flowers Used?

Ornamental

The main use for cardinal flowers is for ornamental value. Their climbing habit make them a wonderful specimen to plant near a wall or a trellis. They also make a wonderful ground cover plant or a container plant.

Wildlife

This is also a wonderful plant option if you’re looking in created a hummingbird garden. Their sweet nectar and particular flower shape make them the ultimate ruby throated hummingbird attractor – so much to the point that many other insect pollinator avoid these plants entirely. They also attract swallowtail butterflies and other butterfly species as well.

Ethnobotany

The roots of the cardinal flower plant have been traditionally harvested and made into tea. This was said to help treat ailments like stomach aches, colds, fevers, and headaches.

Ruby throated hummingbird flying towards dense clusters of red flowers of cardinal flower plant

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