Cardinal flower (Lobelia cardinalis)

Also known as: Scarlet lobelia

The cardinal flower (Lobelia cardinalis) is a perennial herb that reaches heights of 61 to 183 cm. It boasts vibrant red blooms from spring to fall, reminiscent of a Cardinal's robe, which naturally draw hummingbirds. The plant produces blue fruits and its foliage changes color in the fall. It thrives in sunny to partially shaded areas with moist soil, making it ideal for wet garden spots.

In This Article

Care Tips Water Sunlight Temperature Soil Fertilize Prune Propagation Repotting Toxicity

Attributes of Cardinal flower

Lifespan

Perennial

Plant Type

Herb

Plant Height

60 cm to 1.5 m

Spread

30 cm to 60 cm

Leaf Color

Green Red

Flower Size

2.5 cm to 8 cm

Flower Color

Red Pink

Images of Cardinal flower

Quickly Identify Cardinal flower

Lance-shaped leaves with shiny, dark green color, finely-toothed edges, measuring up to 4 inches (10 cm).

Cardinal red flowers in tubular form, about 1.5 inches (3.8 cm) long, with distinctive downward-pointing bend.

Erect spikes (racemes) of bright red blooms with bilabiate structure, blooming from July to October.

Dehiscent capsules turning brown at maturity, about 0.5 inches (1.27 cm) long, releasing tiny seeds.

Herbaceous perennial reaching 4-5 feet (1.2-1.5 meters) tall with clustered lanceolate leaves at the base.

Scientific Classification of Cardinal flower

Phylum

Vascular plants

Class

Dicotyledons

Order

Asterales

Family

Bellflower

Genus

Lobelias

Species

Cardinal flower

Planting and Growing of Cardinal flower

Care Difficulty

Moderate

Watering Schedule

Every 8 days

Sunlight Requirements

Partial sun

Sunshine Duration

6-10 hours

Ideal Temperature

60-80℉

Soil Type

Potting Mix, Peat Mix

Soil pH

6.5-7.5

Fertilizer Type

Balanced

Pruning Season

Spring, Summer

Pruning Area

Branches, Leaves

Pruning Frequency

2 times a year

Repotting Season

Spring

Pot Type

Plastic, Ceramic

How to Water Cardinal flower?

Lobelia cardinalis, known for its stunning red flowers, requires the soil to be consistently moist but not soggy. Each watering session should thoroughly soak the soil, providing around 500ml of water, ensuring the moisture reaches the roots without causing pooling or runoff. This balance is vital for its vibrant growth.

What are the symptoms of an underwatered Cardinal flower? ›

What should I do if my Cardinal flower is not getting enough water? ›

What are the symptoms of an overwatered Cardinal flower? ›

How to save an overwatered Cardinal flower? ›

What Are the Sunlight Requirements for Cardinal flower?

Sunlight Requirements: Partial sun

Duration of light: 4-6 hours per day

Partial sun to partial shade is preferred, with 4 to 6 hours of indirect or dappled sunlight daily. This balance supports flowering and foliage health, ensuring vibrant blossoms and robust growth.

Position for Optimal Growth ›

Adjusting Light for Seasonal Changes ›

Artificial Lighting Options ›

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What Is the Ideal Temperature Range for Cardinal flower?

Ideal Temperature: 60 ~ 80℉

Lobelia cardinalis thrives best when maintained within an ideal temperature range of 60 to 80 degrees Fahrenheit. This temperature range provides a stable environment that supports healthy growth and vibrant blooms, mimicking the plant's native habitat conditions found in temperate climates in North America.

What Soil is Best for Cardinal flower?

Soil type: Loam, Sandy loam, Clay soil

Soil PH: 6.5 ~ 7.5

Lobelia cardinalis prefers soils that retain moisture while not being waterlogged. Loam and sandy loam offer excellent water retention properties without becoming too compact, ensuring healthy growth and vibrant blooms. This plant thrives in nutrient-rich soils. A well-loamy soil provides essential nutrients that Lobelia cardinalis needs for its bright and striking flowers, enhancing both foliage and bloom health. While Lobelia cardinalis enjoys moist conditions, it still requires proper drainage to prevent root rot. Ensuring the soil has adequate drainage helps maintain the plant's root health, leading to robust growth. More About Soil→

How to Fertilize Cardinal flower?

Fertilizer type: Balanced

For Lobelia cardinalis, apply a balanced liquid fertilizer diluted to half strength. The plant does not require heavy feeding, and over-fertilization can harm its growth. Use 1/4 to 1/2 teaspoon per gallon of water during the growing season. More About Fertilizing Techniques→

How to Prune Cardinal flower?

Pruning Time: Spring, Summer

Begin by using clean, sharp scissors or pruning shears. Focus on trimming the plant back by about a third, just above a leaf node. This encourages bushier growth. Remove any dead or damaged stems to prevent disease. It's also beneficial to trim back any wayward stems to maintain a tidy appearance. Deadheading is a specific pruning technique for Lobelia cardinalis that involves removing spent flowers. This process not only cleans up the plant's appearance but also stimulates the plant to produce more blooms. Pinch or cut back spent flower stalks close to the nearest healthy leaf set. More About Pruning Techniques→

How to Propagate Cardinal flower plant?

Propagate Time: Early spring, Late spring, Early summer

Collect the seeds from mature Lobelia cardinalis plants once they have dried out. Ensure the seeds are fully formed and viable for better germination success.

Select healthy stem sections and cut them at a node. Remove lower leaves to prevent rotting when planted, leaving only a few leaves on top.

Dig up a mature Lobelia cardinalis, dividing its root clumps carefully, ensuring each division has roots attached for successful replanting.

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How to Repot Cardinal flower plant?

Repotting frequency: Every 2-3 years

Lobelia cardinalis should be repotted when you notice roots growing out of the drainage holes or circling at the pot's base. This indicates root bound conditions needing more space for healthy growth. It's also time to repot if water isn't absorbing well, suggesting compacted soil.

Opt for a pot that is one size larger than the current one, with sufficient drainage holes to prevent waterlogging. Clay pots are ideal as they allow better aeration, preventing root rot. The slightly larger size gives room for growth without leading to excess soil moisture retention.

Choose a soil blend that's rich in organic matter yet well-draining to maintain moisture without becoming soggy. This helps Lobelia cardinalis to thrive, replicating its natural habitat conditions and promoting vibrant growth and flowering.

Toxicity of Cardinal flower

Is Cardinal flower toxic to humans?

The cardinal flower possesses a mild toxicity throughout its entire structure, typically leading to health issues only if consumed in large quantities. Nonetheless, the toxic threshold varies based on the size and sensitivity of the individual, posing a greater risk to small children. This plant is known to contain harmful alkaloids, such as the genus-specific compounds lobelamine and lobeline. Signs of poisoning may include excessive drooling, nausea, vomiting, abdominal pain, diarrhea, dilated pupils, trembling, seizures, and, in severe cases, coma. It is essential to keep children and individuals with cognitive impairments away from this plant by placing potted specimens out of their reach and either fencing off or removing any plants in your garden.

Is Cardinal flower toxic to cat?

The cardinal flower possesses lobeline, a substance that exhibits moderate toxicity to cats upon ingestion. If a cat consumes a significant quantity, this situation can escalate to an emergency. The toxin is present in every part of the plant. Indicators of poisoning consist of vomiting, drooling, diarrhea, along with signs of depression and lethargy. It's recommended to seek veterinary assistance.

Is Cardinal flower toxic to dog?

The cardinal flower poses a serious risk to dogs. Symptoms can vary from mild to severe, and if you suspect your dog has consumed this plant, it's crucial to seek veterinary assistance without delay. Every part of the cardinal flower contains the toxin lobeline. Consuming small amounts of lobeline typically results in gastrointestinal distress, including nausea, vomiting, diarrhea, fatigue, and/or an irregular heartbeat. Ingesting larger doses of this substance can result in paralysis, unconsciousness, or even fatality.

WARNING

The judgment on toxicity and danger is for reference only. We DO NOT GUARANTEE any accuracy of such judgment. Therefore, you SHALL NOT rely on such judgment. It is IMPORTANT TO SEEK PROFESSIONAL ADVICE in advance when necessary.

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