Cardinal Flower 101 – Ultimate Grow and Care Guide


Cardinal Flower Bloom

Out of all plants native to the United States, one could make a strong argument that the Cardinal Flower has the most striking blooms. A grouping can make a truly eye-catching display that brings in hummingbirds and butterflies alike. After growing these wonderful flowers for years I will now share all that I’ve learned with you!

In this article:

What is Cardinal Flower

Cardinal Flower is a short lived perennial flower native to North America. Scientifically known as Lobelia cardinalis, it will grow to a height of 3-4′ in full sun with moist organic soil. A member of the Campanulaceae family, it will bloom red flowers for six weeks in late Summer and is excellent at attracting hummingbirds.

Native Range of Cardinal Flower. Click on image to enlarge.

The Natural habitat for Cardinal Flower is in wetlands, along streams, ponds, swamps, and anywhere that will stay moist. The Native Range of Cardinal Flower covers much of North America, from California to Florida. North through Nebraska and into Canada / Maine. [1] [2]

Cardinal Flower along a stream

Cardinal Flower is what is known as a ‘short lived’ perennial. It should come back for at least a second year. The longest I’ve had a plant survive was about 5 years.

Reference Table

Scientific NameLobelia cardinalis
Common Name(s)Cardinal Flower
Native Range, USDA ZoneSouthern and Eastern North America, USDA hardiness zone 3-9
Bloom TimeLate Summer-Early Fall
Bloom Duration, Color6 weeks, Red
Height2-4′
Spacing / Spread1-2′
Light RequirementsFull Sun to Partial Shade
Soil TypesLoam, Rich Soil
MoistureWet to Medium Moisture
Fauna Associations / Larval HostsHummingbirds, Butterflies, Bumblebees / hosts pink-washed looper moth

What are the Benefits of Cardinal Flower

Beauty

Blooms of the Cardinal Flower is one of the most beautiful displays you will find with native plants. The dark red flowers last for a long time (over a month long!) and are truly eye catching.

lobelia cardinalis cardinal flower

Red flowers are not very common in North America, really with only a few species such as Red Bee Balm, Fire Pink, and Royal Catchfly. So if you are partial to the color red, you really need to consider adding this flower.

Hummingbirds

The Cardinal Flower really does bring in lots of hummingbirds! They are very attracted to the dark, rich red color of Cardinal Flower. It’s definitely one of the best native plants for attracting hummingbirds.

Wet Areas

Do you have a low spot in your yard? Or perhaps an area that doesn’t drain well? Well, the Cardinal Flower is a great choice for these types of areas. As it does not like to dry out.

Cut Flower

The long bloom time can make the Cardinal Flower a great choice for a vase as a cut flower. So, if you grow a large patch you can have access to some surplus blooms.

Identification and Characteristics of Cardinal Flower

Stalk

The overall shape of this plant is of a single stalk, with occasional branching 2-4′ tall depending on conditions. The stalk is light green in color, round, erect and has hairs.

Leaf

At the base of a Cardinal Flower is a set of basal leaves. First year Plants may only put on this foliage. But, if planted early enough full stalks can develop.

Leaves of the Cardinal Flower are alternate along the stalk and generally about 3″ long by 3/4″ wide and lanceolate in shape. The tips of the leaf come to a sharp fine point, which is one of the ways to distinguish Cardinal Flower with it’s cousin, Blue Lobelia. The edges of the leaf are serrated.

Flowers

The central stalk will produce clusters of red flowers, blooming from bottom to top over a period of roughly six weeks. Flowers are tubular in structure and about 1-2″ long.

There are two narrow petals on the side of the flower below the central tube (raceme) and one large lower petal in the middle with 3 lobes. The tubular flower is upright at a slight angle.

Plants are able to self-pollinate. But their seeds are much smaller, and fewer seeds are produced under self-pollination [3]

About 4-6 weeks after flowering seed pods will develop where the blooms once were. These will be simple ‘capsules’ or pouches that will contain hundreds of seeds each. The seeds themselves are extremely tiny, too small for me to even measure. They are similar to powder and can easily blow from the wind.

Root System

The root system of Cardinal Flower is that of a short taproot.

Grow and Care for Cardinal Flower

Sunlight Requirements

For light requirements, Cardinal Flower prefers full sun (at least 6 hours of sun per day) but can tolerate partial shade (4-6 hours of sun per day). The more sun it receives, the larger and showier the plant will be.

Research has shown that under reduced light, the nectar and seed production drops significantly. Less nectar could likely mean fewer visits from hummingbirds. [4]

It is naturally found in similar habitats as Monarda didyma, such as creeks, rivers, and the edge of ponds, which generally produce dappled sunlight.

Water Requirements

Cardinal flower loves moist soil along the edge of ponds and streams. And it can do well in medium-moist soil too. But this plant should not be allowed to dry out. Cardinal Flower tolerates occasional flooding.

Soil Requirements

Cardinal Flower grows best in rich soils with lots of organic matter. Although I’ve personally grown this flower in poorer soils that I amended with compost. So, adding some organic matter will help this plant grow well.

Although it prefers rich soils, I have successfully grown Cardinal Flower in over-compacted clay-like soil.

Cardinal Flower and fertilizer

If grown in rich organic soil, the Cardinal Flower should not require any supplemental fertilizer. If you have poor soil that is infertile, then you should consider amending with compost, or top-dressing the plant with compost.

How to Grow and Propagate Cardinal Flower from Seed

Germinating Cardinal Flower seeds is rather easy. Most sources suggest to winter-sow or Cold Stratify cardinal flower seed for up to 60 days. But I’ve found that without stratification the seeds will germinate within about 3 weeks.

So, winter sowing is a great option, but in my personal experience is not a requirement.

To grow and germinate Cardinal Flower seeds

  1. Fill a container with moist potting soil
  2. Pinch a small amount of Cardinal Flower seeds between your index finger and thumb. Gently sprinkle this over the potting soil.
  3. Place the container in a location that receives morning sun and afternoon shade (improtant!).
    • The tiny seeds of Cardinal Flower need exposure to light in order to germinate. [1] [2]
  4. Use a pump sprayer or mister to water the pot in the mornings. This will help keep the seeds and potting mix moist.
Cardinal Flower seedlings

In my experience, without stratification germination will take 2-3 weeks. The seedlings are extremely tiny. If your seeds do not germinate in a few weeks, just sprinkle a bit more seed on top. Sometimes the seeds get washed away from rain or heavy watering.

Where to buy Cardinal Flower seeds

We have ordered a variety of native flower seeds from Everwilde Farms, which you can order right from Amazon through our link on our RECOMMENDED PRODUCTS PAGE. (We may earn a small commission when you purchase through our links, at no cost to you. This helps support our website.)

How to save Cardinal Flower seed

To save Lobelia or Cardinal Flower seed, collect the stalks containing the pods about 4 weeks after blooming. Cut the stalks, and carefully tip them upside down into a paper bag. Then, store the bag somewhere cool and dry for another week.

Next, take the stalks out of the bag and pop the individual packets or pouches containing the seed over a paper plate. Next, dump the mixture over a common kitchen strainer to separate the chaff.

Store the completely dry seed in a sealed container in the freezer for long-term storage. If you plant to use the seed the following year, then storing at room temperature in a zip-lock baggy is fine.

But be aware that the viability of Lobelia seed drops very quickly at room temperature. Research has shown that viability drops by half after one year, and then very quickly by the second year. [5]

Below is a detailed video on how to save Lobelia seeds.

Caring for Cardinal Flower seedlings

Like the seeds, the seedlings will be very small. They will generally stay very small until the nighttime temperatures begin to warm up.

I often find that I seed too heavily, as the seeds are so small that it is hard to only plant 5-10 seeds per cell or pot. So, if you have enough containers for the exact number of plants you want, you can pinch or use tweezers to thin the seedlings out.

How to separate Cardinal Flower seedlings

Before attempting to separate Cardinal Flower seedlings, allow the seedlings to grow at least one set of true leaves. It also helps if some of the seedlings begin to increase in size.

Also, plan how many plants you want. That way you don’t end up trying to keep 50 plants when you only want 10!

  1. First prepare additional pots with moist potting soil, and poke a hole in the center.
  2. Then, pop out the Cardinal Flower seedlings / root mass. You can tear the whole cell in half if needed to expose more seedlings.
  3. Carefully grab a seedling by the leaves (not the root) and pull it away from the mass.
  4. Gently place the isolated seedling into the new pot with hole. Gently push the root down the hole. I like to use a pen or pencil to do this, as it helps it get into the hole.
    • Be very careful doing this step. The young roots are quite sensitive. So, only grip the leaves and do not apply any force to the roots.
  5. Carefully push the soil from one side of the pot to the center where the new seedling is located. It helps to hold the seedling up with one hand while moving soil with the other.
  6. Firm up the soil around the seedling
  7. Add more soil as needed to the side that you pushed from.
  8. Mist the pot with a spray bottle or pump sprayer so as not to damage the roots

Cardinal Flower Lifecycle, Growth Rate

Early Spring

In general, the Cardinal Flower will live for 2-4 years, similar to Spotted Bee Balm. It is a short-lived perennial, and I generally start some new plants or direct sow each year to ensure I have some bloom.

But in early Spring new seeds will germinate, and will stay very tiny until night-time temperatures warm up. By July you can expect to have the basal rosette leaves of some plants be 1/2″-1″ diameter. If you transplant out your seedlings by July, you may get some blooms by late August (I’ve done so).

Cardinal Flower doesn’t really ’emerge’ in Spring, as it has a basal rosette of leaves that will be present and evergreen all winter. So, make sure you don’t cover those leaves up! As it can kill the plant.

Summer

In general, the blooming period for Cardinal Flower lasts for six weeks. Starting in mid-June or July, you can expect the central stalk to rise and buds to form. By early August, blooms at the bottom of the plant should begin to open up. As flowers are pollinated, the blooms will work their way up the stalk.

Cardinal Flower Blooms native plant garden

Fall

Approximately 4-6 weeks after blooming, seed pods will form where the blooms previously were located. Each pod will contain hundreds of tiny seeds. This is a great time to sow new seeds directly. Just open a pod in one hand, and pinch some seed and scatter them where you would like new plants.

Winter Care

Once winter sets in, the stalk should die completely and turn brown. BUT – the basal rosette leaves should be present at the base of the plant. At this point you can cut the stalk back to the basal rosette leaves and discard of the stalk.

But do not cover up the Cardinal Flower’s basal rosette leaves, which are evergreen throughout the winter.

Wildlife, Pests, and Diseases associated with Cardinal Flower

Pollinators

Hummingbirds

The Cardinal Flower is one of the best native plants for attracting hummingbirds. Perhaps second only to Red Bee Balm. The red color draws them in, and the flower is reliable for nectar as most bees cannot pollinate it.

If attracting hummingbirds is a goal, you should consider planting Cardinal Flower with Monarda didyma, the Cardinal Climber Vine, and Royal Catchfly or Fire Pink.

Butterflies

In addition to hummingbirds, the Cardinal Flower also is great at attracting large Swallowtail butterflies. Their long probiscus allows them to pollinate the flower.

Bees

Large bumblebees can also pollinate the flower by physically tearing into the side of the tube.

Deer and Rabbits

In general, deer and rabbits avoid eating any member of the Lobelia genus. The foliage contains a poison that dissuades most herbivores.

Dogs and Cats

Per the ASPCA, the Cardinal Flower is toxic to dogs, cats, and even horses. [6] Symptoms include diarrhea and vomiting.

Is Cardinal Flower invasive?

In bare or disturbed areas that are moist, the Cardinal Flower can become aggressive. In more established areas the Cardinal Flower can maintain a presence through self-seeding, but not be overwhelming.

Each plant produces thousands of tiny seeds and they can be dispersed by the wind, somewhat. However, as a native plant it should be called ‘aggressive’ and not invasive. In fact I wish my Cardinal Flower populations were more aggressive!

Deadheading Cardinal Flower

Cardinal Flower should not be deadheaded. I’ve done this, and found that the subsequent blooms from deadheading were insignificant, only a couple of small blooms. Furthermore, it significantly reduced seed production.

Disease

Leaf Spot / Fungus

Late in the season the leaves can get leaf-spot fungus or mildew. In my experience, the effects are primarily cosmetic and are not fatal to the plant. The image below was taken in September, so very late in the season.

Cardinal Flower Leaves turning yellow

If you notice the leaves of Cardinal Flower turning yellow, it can often be a nutrient deficiency in the soil. I’ve corrected this problem by top-dressing with compost when growing in poor suburban orange, inorganic soil.

Cardinal Flower drooping

During summer, you may notice the stalk of Cardinal Flower bent or drooping. This is normal, and the plant will grow out of it naturally.

Just be patient, as it is likely that this is just the growing process similar to how Sunflowers change direction as they grow. I’ve actually taken a 15 minute video where you can observe a drooping stalk begin to straighten up.

Where you can buy Cardinal Flower

Cardinal Flower is available for purchase at many nurseries. Although the ‘big box’ stores generally only have hybrids or cultivars. So, if you are interested in buying the straight native species, be sure to read the scientific name on the label.

Varieties of Cardinal Flower

There are numerous hybrids and cultivars of Cardinal Flower available. Some of these are grown for their color, while others for different foliage. Some of the varieties include:

Black Truffle Cardinal Flower has dark, almost black leaves and bright red flowers.

Lobelia fulgens ‘Queen Victoria’ has dark red flowers and darker foliage (similar to beet leaves).

Lobelia x speciosa which is a hybrid between Lobelia cardinalis and Lobelia sphilitica. It was first described as naturally occurring in 1876 in Illinois. [7]

Purchase Seed

We have ordered a variety of native flower seeds from Everwilde Farms, which you can order right from Amazon through our link on our RECOMMENDED PRODUCTS PAGE. (We may earn a small commission when you purchase through our links, at no cost to you. This helps support our website.)

Uses of Cardinal Flower

Garden Uses

The Cardinal Flower is very versatile in the garden. In fact, with some supplemental watering you can grow it almost anywhere. It’s a great choice for any manicured flower bed that has plenty of access to water, as I’ve grown some in a drier area and had to water during drought. The plants still thrived and bloomed nicely.

Near ponds, streams, bogs

If you have any water features on your property, the Cardinal Flower would fit nicely. They naturally grow along pond and stream edges. Additionally the Cardinal Flower would be an excellent choice for a rain garden, as it can tolerate occasional flooding.

lobelia cardinalis cardinal flower

As a wildflower

I’ve grown it in a partially shaded area of our backyard micro-prairie. I just scattered some seed and had several plants come up the following year.

It wasn’t self-sustaining, as the competition is quite high and the area can get a bit drier. But the surrounding vegetation shades the soil quite well, which helps keep moisture around.

Companion Plants of Cardinal Flowe

Some nice companion plants that bloom the same time as Cardinal Flower would be White Turtlehead, Great Blue Lobelia, and Ironweed.

For some nice companion plants that bloom before Cardinal Flower, Liatris Spicata, Swamp Milkweed and Monarda didyma would make great choices as they also like wet soil.

Septic Fields

Due to it’s love of moisture, the Cardinal Flower makes a great plant to grow in septic fields. It will grow well, not be bothered by anything, and still attract hummingbirds. This is known as making the best of a stinky situation!

Containers

The Cardinal Flower can be grown in pots and containers. If you have large (3 gallon+) containers, you can grow Cardinal Flower in them. Just make sure they have plenty of access to water. If you want smaller plants, just use a smaller pot.

Edible

Cardinal Flower is not an edible plant, as the leaves contain the poison lobeline. This compound can be toxic in large quantities and cause nausea, diarrhea, and vomiting. [8] [9]

Medicinal

There are over 34 documented medicinal uses of Cardinal Flower by Native Americans. Medicinal uses ranged from pain/cold medicine, swelling, treating syphilis, to stopping nosebleeds. [10] [11]

Of the 5 tribes that utilize Cardinal Flower for medicine, the Cherokee and Iroquois had the most uses. Some of these uses include the following:

  • Compound of leaves used to cure headache
  • Infusion of root taken for worms
  • An infusion was used to treat rheumatism, colds,
  • A poultice of root used to heal sores or ‘risings’
  • Infusion of leaves used to treat fever
  • It was used to treat croup in babies
  • Used as a love medicine

Read More Native Plants Here

References:

[1] – USDA Plants Database, Natural Resources Conservation Serivce. https://plants.usda.gov/home/plantProfile?symbol=LOCA2

[2] – Moore, Fisher, Della Torre III, Gettys. Native Aquatic and Wetland Plants: Cardinal Flower Lobelia cardinalis. University of Florida IFAS Extension, SS-AGR-398, 2020, https://journals.flvc.org/edis/article/download/127701/128100

[3] – Schlichting, C.D. and Devlin, B. (1992), POLLEN AND OVULE SOURCES AFFECT SEED PRODUCTION OF LOBELIA CARDINALIS (LOBELIACE AE). American Journal of Botany, 79: 891-898. https://doi.org/10.1002/j.1537-2197.1992.tb13671.x

[4] – Devlin, B. (1988), The Effects of Stress on Reproductive Characters of Lobelia Cardinalis. Ecology, 69: 1716-1720. https://doi.org/10.2307/1941149

[5] – Barton, L. V., Storage of seeds of Lobelia cardinalis L., Contributions. Boyce Thompson Institute for Plant Research 1960 Vol.20 pp.395-401 ref.bibl. 15. https://www.cabdirect.org/cabdirect/abstract/19610301082 (retrieved 16JUN2021)

[6] – Poison to dogs – https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/lobelia

[7] – John Ebinger, Lobelia Cardinalis x L. Siphilitica in Illinois. Transactions of the Illinois Academy of Science, Vol 78, pp.29-31, 1985. http://ilacadofsci.com/wp-content/uploads/2013/09/078-04-print.pdf

[8] – Liana Dantas da Costa e Silva, Laise Carla Lima Verde Rodrigues, Viviane Ramos dos Santos, Mariangela da Costa Allgayer, Alexandre de Barros Falcão Ferraz, Helena Campos Rolla, Patrícia Pereira, Jaqueline Nascimento Picada, Evaluation of mutagenic and genotoxic activities of lobeline and its modulation on genomic instability induced by ethanol, Life Sciences, Volume 103, Issue 2, 2014, Pages 73-78, ISSN 0024-3205, https://doi.org/10.1016/j.lfs.2014.03.034.

[9] – Angel Josabad Alonso-Castro, Fabiola Domínguez, Alan Joel Ruiz-Padilla, Nimsi Campos-Xolalpa, Juan Ramón Zapata-Morales, Candy Carranza-Alvarez, Juan Jose Maldonado-Miranda, “Medicinal Plants from North and Central America and the Caribbean Considered Toxic for Humans: The Other Side of the Coin”, Evidence-Based Complementary and Alternative Medicine, vol. 2017, Article ID 9439868, 28 pages, 2017. https://doi.org/10.1155/2017/9439868

[10] – http://naeb.brit.org/uses/species/2221/

[11] – William A. Emboden, American Folk Medicine, Plant Hypnotics among the North American Indians, University of California Press | 1976. https://doi.org/10.1525/9780520336773-015

Joe Foster

Hi - I grew up outdoors in nature - hiking, fishing, hunting. In high school I got my first job at a garden center where I learned to garden and landscape. I've been growing plants from seed and designing native plant gardens for over six years. I hope to share some of my knowledge with you! Additionally I am a wood worker / DIY enthusiast. I enjoy designing/building projects (with hand tools when I can!). I hope to give you some tips and useful information!

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