Tall larkspur – A Complete Guide To Delphinium Exaltatum

Tall Larkspur is a perennial wildflower native to Eastern North America. Scientifically known as Delphinium exaltatum, it blooms tall spikes of blue to purple flowers from July to September. Growing 4-6′ tall along woodland edges and forest clearings in the Appalachian Mountains, the showy flowers attract bees, butterflies, and hummingbirds.

I’ve been growing Tall Larkspur in my gardens since about 2020 when I first grew them from seed, and have had it in my gardens since then. I’ve had them in formal flower beds since then, and have even successfully transplanted mature specimens. So, you could say that I’ve gotten to know this flower very well!

In this article:

• What is Tall Larkspur
• What are the benefits of Tall Larkspur
• Identification / Characteristics
• How to grow and care for Tall Larkspur
  • How to grow plant from seed
• What Wildlife, Pests, and Diseases effect Tall Larkspur
• Where to buy Tall Larkspur
• Uses of Tall Larkspur
• Final thoughts

What is Tall Larkspur

The latest blooming member of the Delphinium genus, Tall Larkspur is also quite possibly the longest bloomer with flowers lasting until a hard frost. A residential-friendly native plant, it can make for a long showy display in formal flowerbed, meadow, or border garden. [1][2][3]

Toxicity

Like other members of the Delphinium genus, Tall Larkspur is very toxic to both humans and most animals. It contains Alkaloids delphinine, ajacine, and possibly others. [4][5] Younger plants and seeds are the most toxic parts.[15] But nonetheless, train your children to never eat a plant without your approval!

Native Range of Tall Larkspur

The native range of Tall Larkspur is disjointed. The primary range is in the Appalachian Mountains from Pennsylvania to North Carolina. Isolated pockets exist in the Ozarks as well. The disjointed range is most likely due to glacial drift/wash, and flooding during interglacial periods.[6]

Often a rare plant, Tall Larkspur is listed as endangered in Maryland, North Carolina, Pennsylvania, and Tennessee. [6][7]

The typical natural habitat of Tall Larkspur is dry open deciduous woodlands, the edge of forests, on exposed Southwest facing slopes, or in open cedar barrens or glades. [2][7]

Reference Table

Scientific Name	Delphinium exaltatum
Common Name(s)	Tall Larkspur
Native Range, USDA Zone	Eastern United States, USDA Hardiness Zone 5-7
Bloom Time	Summer-Fall
Bloom Duration, Color	Two months, blue to purple
Height	3-5′ (90-150 cm)
Spacing / Spread	1-2′ (30-60 cm)
Light Requirements	Full sun
Soil Types	Sandy loam, fertile soils, clay loam
Moisture	Moist to medium-moisture, well-drained
Fauna Associations / Larval Hosts	Bees, butterflies, hummingbirds

What are the Benefits of Tall Larkspur

Tall Larkspur is an attractive native plant that is suitable for formal flower beds in a residential area. Typically growing 3-4′ tall, it’s bloom last a long time from July to September and can attract a variety of wildlife. In addition to birds, butterflies, and hummingbirds, the stalks are often strong enough to act as a perch for birds. [10]

Although most references state it will stop blooming in Autumn, I’ve actually seen mine go right on into Winter. So you may get color out of these well into Fall, possibly even longer than Aromatic Aster. And these flowers can also make for a good accent of focal point of a floral bouquet, as Tall Larkspur makes a great cut flower.

Identification and Characteristics of Tall Larkspur

Stalk

Tall Larkspur can grow to an overall height of 6′ tall (2m). The stems/stalk is smooth and erect. The base is reddish green while the upper portions of the stem are light green. [2][6]

Leaf

Lover leaves of Tall Larkspur have 2-5″ (2-15 cm) stems (petioles) that are deeply & palmately divided into 5 sections, with 3-7 round lobes, and oblanceolate to elliptic-linear in shape. The overall size of a lower leaf is around 2-4″ wide by 1-3″ long. [6][11]

Further up the stem alternate leaves with fewer lobes and shorter petioles occur.

Flower

Along the stem, 8-30 flowers will occur in racemes attached with 1/2″-1″ stems (pedicels). Individual blooms are spurred, tubular, and about 1.5-2″ long by 1/2″ diameter. [2][11]

Saving seed

One can save seed from Tall Larkspur. About 6 weeks after flowering capsules will form where the flowers once were. Each capsule will contain a number of small seed.

When the capsules turn brown, cut the stalk below the capsules and place in a brown paper bag vertically. If you tip the stalk upside down, seed may fall out.

Let the capsules sit inside the bag for about a week in a cool dry place. Then, simply pop open capsules to have the seed fall out. You can sift the seed through a strainer to reduce the amount of chaff.

Seed can be stored for at least a year or two after harvesting in an envelope or zip-lock bag. Better viability will likely occur if stored sealed in the fridge.

Root

The root system of Tall Larkspur emerges from a strong caudex, with fibrous, fleshy branching taproots that are fairly shallow. It can easily be transplanted in late Fall or early Spring.

Grow and Care for Tall Larkspur

Sunlight Requirements

As a general rule, Tall Larkspur will prefer full sun, which is at least six hours of direct sunlight per day. However in it’s southern range it will benefit from having a bit of afternoon shade to shelter it from the hottest parts of the day. [10]

As a side note, it has been noted that while most known populations in the wild prefer full sun, Tall Larkspur that grows wild in the Ozarks can be found in deep shade.[6] But unless you know the origin of your species is from the Ozarks, you should plant it in full sun.

Soil Requirements

For soil requirements, Tall Larkspur will grow well in anything from sandy loam, loam, or clay loam. The key is to make sure the soil drains well.

Moisture Requirements

For moisture, Tall Larkspur prefers moist to medium-moist soil that drains well. In poorly draining soils it may be susceptible to root rot. [12]

Maintenance

If planted in the open and exposed to wind, Tall Larkspur may be blown over in heavy storms/winds. In that case staking may be required.

Fertilizer

Tall Larkspur does not require fertilizer. It grows well in poor soils. If grown in rich soils, it may grow too tall and be prone to falling over.

How to Grow Tall Larkspur from Seed

Tall Larkspur seeds require a cold-moist stratification period of 60-90 days to break dormancy.[13] You will likely get the best results by Winter Sowing the seed (I’ve germinated it a couple times using this method).

Steps to germinate Tall Larkspur seed

The following process assumes you have either cold stratified your seed in the refrigerator for 60-90 days, or are going to Winter Sow the seed.

1. Fill a suitable container with moist potting soil. It should be moist enough when you squeeze a handful, a few drops of water fall out.
2. Plant 3-5 seeds just under the soil surface, 1/16″ (1 mm) deep.
3. Place the container in a location that receives morning sun and afternoon shade
4. Germination should occur sometime after soil temperatures warm to 68F (20C)

Wildlife, Pests, and Diseases associated with Tall Larkspur

Pollinators

Tall Larkspur attracts long-tongued bees, butterflies, and hummingbirds. The long bloom time make it a valuable food source that feeds pollinators into Autumn.

Livestock

Tall Larkspur is toxic to livestock. Poisoning of cattle who grazed on the plants was first recorded in the 1700’s. [5]

Deer and Rabbits

The toxic nature of the foliage of Tall Larkspur makes it very disease resistant. I’ve never noticed damage to any of my plants. [4]

Dogs and Cats

Like all members of the Delphinium genus, Tall Larkspur (D. Exaltatum) is toxic to dogs and cats. [14]

Disease

Root rot is the most prevalent disease to harm Tall Larkspur. It is a potentially fatal fungus arising in soil that has poor drainage, structure, and oxygen. Although there are many different pathogens that can cause root rot, Sclerotium rolfsii is the most common manifestation. You will notice entire shoots turning brown and dying in a single day. This will continue until there are none left, at which point the plant is likely dead. [12]

If you notice these symptoms, you may wish to try to improve drainage at the location or move the plant to a location that has better drainage. It is a serious disease, and I have had other plants (such as Winecups) fall victim to it.

And as always, if you are unsure what kind of drainage you have, you can learn to test it here.

Where you can buy Tall Larkspur

Tall Larkspur is not typically sold in nurseries, as it is a more rare native plant, and most nurseries and greenhouses sell cultivars or other hybrids of Delphinium genus. But it can be purchased at specialty nurseries that deal in Native Plants. You can find native plant nurseries near you on our interactive map.

But should you happen upon a plant in a big-box store or garden center being sold as ‘Larkspur’, be wary. Make sure you find the botanical name to make sure it is the correct species and not a cultivar.

Where to buy 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.)

Uses of Tall Larkspur

Garden Uses

Tall Larkspur is best used as a focal point of a cottage style garden, native garden, or in the back (North) side of a formal flowerbed due to it’s height. It can be used as an attractive border flower that is long lived, and can bloom for over half the growing season.

Companion Plants

With the primary requirement for growing conditions being that it has well-draining soil, Tall Larkspur can grow nicely with a huge number of flowers. Some suggestions of flowers that would grow well paired with Tall Larkspur include the following:

• Echinacea purpurea
• Perennial Black Eyed Susan
• Blue Lobelia
• Sneezeweed
• Aromatic Aster
• Smooth Blue Aster
• New England Aster

In a wildflower meadow or micro-prairie, Tall larkspur will pair well with Brown Eyed Susan, Tall Sunflower, or any Goldenrod (provided Canadian Goldenrod doesn’t overtake it).

Medicinal Uses

No medicinal uses of Tall Larkspur exist, as the plant is highly toxic to humans and animals. If eaten in sufficient quantity symptoms may present themselves including upset stomach, twitching, cramps/bloating, paralysis and death.[15]

Final Thoughts

Tall Larkspur is a very attractive elegant looking Native Plant that fits in many landscaping situations, and definitely in more formal flower beds. It’s long bloom time should give it extra value when considering what flowers to use when designing a Native flower bed. The wildlife that it will attract also give it special interest.

Find more native plants here