Larkspur

Larkspur, belonging to the genus Delphinium within the buttercup family Ranunculaceae, is a group of highly popular annual and perennial flowering plants famous for their towering, vertical flower spikes. Native throughout the Northern Hemisphere and high-altitude tropical mountains of Africa, larkspur has long been a staple of classic cottage gardens, admired for its intense blue and purple colors, which are rare in the botanical world.

Growing as upright, slender herbaceous plants, larkspurs range from 2 to 6 feet in height. They feature deeply divided, feathery green leaves alternate on the stems. The spectacular flowers are arranged in dense terminal spikes, featuring a unique structure where a backward-pointing nectar spur is formed by the upper sepal, giving the flower its common name 'Larkspur' (resembling the spur of a lark's claw). The stems are hollow and lack thorns.

The reproductive morphology of Delphinium is represented by the formula % ⚥ K5 C4 A∞ G3-5. The flowers are bilaterally symmetrical (zygomorphic) and bisexual. The colorful 'petals' are actually 5 petal-like sepals, with the top one forming the long spur. The true corolla consists of 4 small petals (two forming nectar spurs inside the outer sepal spur, and two forming a fuzzy 'bee' center). The androecium has numerous stamens, and the gynoecium contains 3 to 5 separate carpels forming superior ovaries.

Larkspurs are cool-season plants that thrive in full sun and well-draining, moist, organic-rich alkaline soils. They require cool summers to perform well, as high heat and humidity will cause the plants to decline rapidly. They are easily grown from seeds sown directly in autumn or early spring. Larkspurs grow successfully in USDA zones 2 through 10.

Despite their visual appeal, larkspurs are extremely toxic to humans and household pets. All parts of the plant, especially young shoots and seeds, contain high levels of diterpene alkaloids (primarily delphinine). Ingestion triggers neuromuscular blockade, muscle stiffness, drooling, tremors, respiratory paralysis, convulsions, and cardiac arrest, which can be lethal within hours. Larkspur is a critical emergency hazard for cats and dogs.

Larkspur is easily identified by its tall vertical spikes of spurred blue/purple flowers and feathery leaves. It is often confused with Monkshood, but distinguished by the spur rather than a rounded hood. In cottage borders, it pairs beautifully with snapdragons and hollyhocks. To study more cottage garden annuals, browse our Flower Identifier.