While often used interchangeably in gardening circles, Delphiniums and Larkspur represent a key botanical distinction. All true Larkspurs are, in fact, a specific type of Delphinium. The genus Delphinium is a large group within the Ranunculaceae (buttercup) family. The common name "Larkspur" is typically reserved for annual species within this genus, most notably Delphinium ajacis (syn. Consolida ajacis) and Delphinium consolida. In contrast, the plants most gardeners refer to as "Delphiniums" are the towering, majestic perennial hybrids, primarily derived from species like Delphinium elatum. Therefore, all Larkspurs are Delphiniums, but not all Delphiniums are Larkspurs.
The most significant difference lies in their lifecycle. True perennial Delphiniums are herbaceous perennials. They establish a root system that survives winter and sends up new growth each spring, often living for several years, though they can be short-lived. They form a dense, multi-stemmed clump. Annual Larkspur, conversely, completes its entire life cycle—germination, growth, flowering, seeding, and death—within a single growing season. It relies on self-seeding to return to the garden the following year. Its growth habit is generally more airy and finely textured, with branching stems, compared to the robust, upright clumps of perennial Delphiniums.
Close examination of the foliage provides a clear identification clue. Perennial Delphiniums possess leaves that are large, palmately lobed, and divided into several-to-many pointed segments. They are held on sturdy, often hollow, stems that require staking to support the heavy flower spikes. Annual Larkspur has distinctly different foliage. Its leaves are finely dissected, almost feathery or fern-like in appearance, and are alternate and much more delicate. The stems are also more slender and wiry, typically requiring less support.
Both produce showy terminal racemes, but their structure differs. Perennial Delphinium flowers are densely packed on a tall, single, central spike, creating a dramatic, solid column of color. The individual flowers have five petal-like sepals and a central bee, or eye, which is actually the petals fused together. Annual Larkspur flowers are arranged on a more open, branching raceme, creating a looser, less formal cluster. A key taxonomic feature is the number of petals: Larkspur (Consolida) flowers have a single united petal, while perennial Delphinium flowers have a pair of separate petals.
For the definitive identification, one can examine the seedpods (follicles) after flowering. This is the characteristic that originally led botanists to separate the annual types into the Consolida genus. Perennial Delphiniums produce seedpods that are clustered in groups of three (trifollicles). In contrast, annual Larkspur produces its seeds in a single, elongated, and unfused pod (a follicle). This solitary pod is a foolproof way to distinguish the two at the end of their blooming season.
