Tall larkspur
Also known as
Delphinium, Candle delphinium, Candle larkspur
Keep this plant’s care guide close at hand.
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Delphinium elatum, commonly called tall larkspur, is a stately herbaceous perennial prized for its towering spires of densely packed florets in shades of blue, violet, indigo, white, and pink. Plants typically reach 1.2–2 m tall with deeply lobed, palmate leaves and hollow, upright stems that benefit from staking. A magnet for bees and other pollinators, D. elatum has given rise to many garden hybrids and selections known for bold color and strong vertical accents in borders and cottage gardens. It thrives in cool-summer climates with fertile, moist, well-drained soils and appreciates consistent moisture without waterlogging. Deadheading can encourage a secondary, shorter flush after the main early-summer bloom. Although long-lived in ideal conditions, it is often short-lived in hot, humid regions and may require periodic replanting. All parts are toxic if ingested due to diterpenoid alkaloids, so site away from livestock and curious pets. Excellent as a cut flower when stems are harvested just as lower florets open.
Taxonomy
Properties & Requirements
How to care for Tall larkspur
Water
Keep soil evenly moist but never waterlogged. Provide roughly 2.5 cm (1 inch) of water per week, more during heat or sandy soils. Water deeply and infrequently to encourage a robust root system, ideally in the morning so foliage dries quickly. Avoid wetting the crown persistently, which predisposes plants to rot. Apply a 5–8 cm mulch to moderate soil temperature and reduce evaporation, keeping mulch slightly back from the crown.
Light
Provide full sun (6–8 hours) in cool or mild climates for the strongest stems and best flowering. In hot-summer regions, offer morning sun with light afternoon shade to reduce heat stress and mildew. Avoid deep shade, which leads to weak, floppy growth and fewer blooms. Ensure good air circulation around plants to limit foliar diseases, especially in humid conditions or densely planted borders.
Nutrients
Delphinium elatum is a heavy feeder. In early spring, incorporate compost and apply a balanced, slow‑release fertilizer (e.g., 10‑10‑10). During active growth, supplement every 2–3 weeks with a dilute liquid feed. After the first bloom, switch to a lower‑nitrogen, higher‑potassium ratio (e.g., 5‑10‑10) to strengthen stems and support rebloom. Avoid excessive nitrogen, which encourages weak, floppy growth and disease. Maintain a 5–8 cm organic mulch to conserve moisture and steadily release nutrients.
Temperature
Hardy in USDA Zones 3–7, D. elatum prefers cool summers. Optimal growth occurs with days around 15–24°C (59–75°F) and cool nights. Prolonged heat above ~29°C (85°F) stresses plants; provide afternoon shade and extra water during heat waves. In winter, crowns tolerate deep cold with good drainage; avoid saturated soils. Protect tender spring shoots from late frosts with cloches or light covers if needed.
