The terms Delphinium and Larkspur are often used interchangeably, leading to considerable confusion. However, from a botanical perspective, there are clear distinctions between them, primarily relating to their genus classification, morphology, and life cycle. While all Larkspurs are Delphiniums, not all Delphiniums are Larkspurs.
The primary difference lies in their scientific classification. Both belong to the Ranunculaceae (buttercup) family. However, the genus Delphinium is broad. The common garden flowers most people refer to as "Delphinium" are typically perennial species within this genus, such as Delphinium elatum and its many hybrids. "Larkspur" is the common name traditionally applied to annual species of the genus Delphinium. Notably, some botanists have classified the annual varieties into a separate genus, Consolida. Therefore, you may see Larkspur referred to as Consolida ajacis (syn. Delphinium ajacis) or Consolida orientalis. This reclassification is a point of debate, but it underscores the fundamental biological difference between the perennial and annual types.
The growth habit and physical structure of these plants offer clear visual cues. True perennial Delphiniums are known for their towering, robust flower spikes, which can reach heights of 4 to 6 feet or more. They form a central, multi-stemmed clump with a woody base that survives winter and regrows each spring. Their flowers are densely packed on the spike, and each individual flower has a "bee," a group of five petal-like structures, including a prominent backward-pointing spur. In contrast, annual Larkspurs (Consolida spp.) have a much finer, more feathery texture. They are typically bushier and more branching, with a central spike and many side branches, growing to a modest 1 to 3 feet tall. Their foliage is more finely dissected, almost fern-like, compared to the larger, palmate leaves of perennial Delphiniums. The flowers on a Larkspur spike are more loosely arranged.
This is the most practical difference for gardeners. Perennial Delphiniums are long-lived plants that return for several years from the same root system. They require rich, well-drained soil, consistent moisture, and often need staking to support their heavy flower spikes. They are typically grown in USDA hardiness zones 3-7. Annual Larkspurs, as their classification implies, complete their entire life cycle—germination, growth, flowering, seed production, and death—within a single growing season. They are prized for their ability to self-seed readily, often creating delightful, naturalized drifts of color in gardens the following year. They are generally more heat-tolerant and easier to grow from seed directly sown in the garden in fall or early spring.
It is important to note that all parts of both perennial Delphiniums and annual Larkspurs are highly toxic to humans, livestock, and pets if ingested. They contain various diterpenoid alkaloids, such as methyllycaconitine, which can cause severe digestive upset, neuromuscular paralysis, and can be fatal. This toxicity is a shared characteristic across the entire genus.
