Cardinal Flower Facts, Care & Seeds Guide (Lobelia cardinalis)

Pond Informer is supported by its readers. We may earn commission at no extra cost to you if you buy through a link on this page. As an Amazon Associate we earn from qualifying purchases.

a mature, healthy cardinal flower with many red flowers
Cardinal flower is a visually striking and attractive marginal plant, which has become naturalised throughout many areas.

Cardinal flower (Lobelia cardinalis), also called ‘Queen Victoria,’ is a very visually striking, unique flower belonging to the bellflower (Campanulaceae) family. Native to North and South America, cardinal flower was introduced to various portions of Europe in the 1600’s via early explorers of North America bringing plants of interest back to their homes in the Old World. It has since become naturalized, meaning that it’s not considered invasive in Europe as it doesn’t tend to overtake areas or outcompete native plants.

With its bright scarlet petals, tubular flower shape, and sweet nectar, cardinal flower is a favorite of hummingbirds, but is also readily visited and pollinated by butterflies and moths (such as the hawk moth) with longer proboscises that are able to access to nectar.

Facts, Benefits & Uses of Cardinal Flower (Queen Victoria) 

A hummingbird getting nectar from cardinal flower
Cardinal flower is a favourite of hummingbirds, moths and butterflies and will work great to attract them.

The long, tubular bell-like flowers make it difficult for other insects or birds to utilize this plant, making it of particular importance to hummingbirds and butterflies, with the plant depending upon these organisms and vice versa. Several moth and butterfly species lay their eggs on lobelia species, including cardinal flower. Once eggs hatch, pupae and caterpillars can be found on the small leaves, which in turn feed new-born and juvenile birds.

Lobelia cardinalis is often used in constructed wetlands where water filtration as well as aesthetics are important, as the flowers are of course visually striking. Though it certainly doesn’t provide as much nutrient and pollutant filtration as plants like native cattails that have extensive roots systems, cardinal flower, like most marginal plants, does help to filter out some excess nutrients and pollutants from the water.

Check Pond Plant Prices

Cardinal Flower Fact Sheet:
Herbaceous Perennial
USDA 2-9
Full Sun, Partial Shade, Full Shade
Bright Red
May – October (Summer to Fall)
0.6 – 1.2 m (2–4 ft.) tall, 1-2 inch blooms
up to 5.08 cm (2 in) water depth, or damp soil
pH 6.0-7.5

Cardinal Flower Growth, Hardiness & Climate

a vibrant lobelia cardinalis growing on the edge of a pond
Stan Shebs [CC BY-SA 3.0], via Wikimedia Commons

Cardinal flower takes approximately two years to fully establish and grow to its adult form. The first year, there will only be a rosette of leaves on the ground, each leaf spanning up to 6 inches long. The second year, a stalk will form and the plant will bloom and drop seeds for the following year. As it occurs widely in nature throughout the Americas, cardinal flower is fairly hardy, able to sustain temperatures well below freezing as well as those exceeding 90° F, so long as soil is kept damp or saturated.

They are able to tolerate full sun, partial shade, and full shade, again so long as they have access to plenty of moisture. Plants typically reach a maximum height of around four feet, though up to six feet is possible. The basal rosette will span between six inches and two feet in diameter (about a foot is average for most cardinal flower plants).

How to Plant Cardinal Flower In Ponds

red lobelia cardinalis with many flowers growing near a pond
H. Zell [CC BY-SA 3.0], via Wikimedia Commons

Cardinal flowers are marginal plants that can be planted in one to two inches of standing water or in consistently damp soil. In the wild, they are most often found along the banks of rivers, lakes, ponds, and wetlands where their roots can constantly access water. They can also be found in damp woods and moist meadows.

If planting from seeds, place the seeds in damp soil about half an inch to an inch below the soil surface. If planting established plants, you can plant in either damp soil along the edge of your pond with the stem about one to two inches beneath the soil surface (with the taproot, of course, completely buried), or directly in the water up to two inches deep. If the plant is not yet well established, try placing it in a weighted pot to help keep it beneath the water until its roots are more established and can hang onto the pond substrate without floating away. They do well in saturated soils such as loam and clay as well as well-drained soils like gravel or sand – so long as they have plenty of access to water – but do best in rich, loamy or humus soils.

How to Care For & Maintain Cardinal Flower

cardinal flower with many red flowers and buds near a pond
R. A. Nonenmacher [CC BY-SA 4.0], via Wikimedia Commons

Not much care is required; really, the main thing that you need to do is ensure that the soil never ever dries out, as this plant is not at all drought-tolerant. You won’t need to prune foliage, but do be sure to clean up any dropped leaves or flowers to prevent your fish from eating them and to maintain water quality. Clip off any dead flowers or leaves that are still attached to the plant.

How to Winter Cardinal Flower:

Cardinal flower is a hardy evergreen perennial that, if planted in soil, should be just fine if left outside for the winter. Its flowers and stems will of course die off in the autumn, but evergreen basal rosettes will remain over the winter and should sprout new growth the following spring. Seed pods will also drop seeds in the autumn, and these may also germinate in the spring.

If planted in standing water, you may want to dig up any lobelia cardinalis plants and transfer them to either outdoor pots above water or bring them inside, as freezing water may damage the basal rosettes and negatively impact growth the following year. You can also harvest seeds from the dried seed pods/capsules on the plant in the fall, or buy new ones, and plant them the following spring.

Is Cardinal Flower Toxic, Poisonous or Invasive?

A cardinal flower growing in a pond that may cause toxicity if dropped vegetation isn't removed from the pond
Stan Shebs [CC BY-SA 3.0], via Wikimedia Commons

All parts of lobelia cardinalis are toxic due to the presence of the toxic alkaloids lobelamine and lobeline, which are present in all lobelia species. Potential symptoms of toxicity include vomiting, weakness, nausea, joint inflammation, convulsions, and even coma if enough is consumed. Do not allow your fish to eat any parts of the plant, and as always remove any dead parts from the water.

As mentioned previously, cardinal flower is widespread throughout North and South America, and is not considered invasive in Europe as it’s had several hundred years to become naturalized there. It’s not a particularly competitive plant, so it won’t choke out other vegetation. Because of this, its technical classification outside of the Americas would be “non-native,” rather than invasive.

Is Cardinal Flower Edible? Will Fish Eat it?

Cardinal flower is toxic, and as such is not edible. Pond fish don’t seem to find the plant particularly palatable, but just in case be sure to plant where fish cannot possibly nibble on it. Plant it either in saturated soil outside of the pond, or, if you would like to have it in the pond, plant it in a pot so that your fish can’t get to the roots or stem, or on a shelf that is too shallow for any of your fish to swim to. It’s toxic to most mammals as well, including humans, dogs, and cats, so if needed put up a fence to prevent pets and children from getting into the plant.

Most wild animals know to not eat toxic plants, but the same cannot always be said of kids or domesticated animals. If you suspect that critters getting into lobelia may be an issue, avoid planting members of this genus altogether.

Where to Buy Cardinal Flower Seeds? (UK & US)

Cardinal flower is readily available at most pond retail stores and plant nurseries, as well as online. Though it can be found in most riparian habitats in North America and portions of South America, please do not take wild plants as many natural cardinal flower communities are struggling due to being overpicked. Appreciate wild lobelia cardinalis by leaving it be, and purchase your own from a sustainable nursery that grows their own.

Check Pond Plant Prices

1 thought on “Cardinal Flower Facts, Care & Seeds Guide (Lobelia cardinalis)”

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.