Scarlet larkspur: complete guide

The Scarlet larkspur (Delphinium cardinale), also called Cardinal delphinium or Cardinalriddarsporre, is a stunning flowering plant from the Ranunculaceae family. This American wildflower grows naturally in dry mountain regions from California to Mexico. The most striking feature is the brilliant scarlet-red to orange flowers arranged in long, dense spikes.

Overview

Delphinium cardinale is a perennial to short-lived annual plant originating from western North America. Native to southwestern California coasts and Baja California Norte, this plant thrives in warm, dry summers and mild winters. The plant is renowned for its vivid red flowers, a color rare among wild larkspurs, making it exceptionally attractive to garden designers.

Appearance and Bloom

The plant grows upright, typically 60 to 100 centimeters tall, with deeply lobed, palmately-divided leaves growing elegantly from the stem. The flowers are the true star: long, slender spikes with numerous florets in pure scarlet-red, sometimes with orange tint. Each flower has four sepals (two extended into spurs) and two petals with characteristic feathery nectaries. Blooming period runs from May to July, extending to August in optimal conditions.

Ideal Location

Scarlet larkspur prefers warm, sunny climates with well-draining soil. Plant in full sun, at least 6 to 8 hours daily. In warm regions (USDA 8-10), it grows as a perennial. In temperate zones, it functions better as an annual or summer bloomer. Group multiple specimens for visual impact. Ensure standsite has excellent drainage without stagnation.

Soil

Soil must be well-draining, gritty or sandy with some humus. pH can be neutral to slightly acid (6.5-7.5). Delphinium cardinale tolerates calcareous soils well. Add sand and gravel to heavy clay soils. The plant performs better on modest soils; excessive fertility promotes foliage at the expense of flowers. Drainage is critical; waterlogging causes root rot and plant decline.

Watering

This species prefers dry climate after establishment. Young plants need more moisture: water regularly during the first growing season. Once established, water when the top 5 centimeters feel dry. Winter watering should be sparing. The plant is drought-tolerant once deep-rooted, so overwatering is a greater problem than underwatering. During extreme dry periods, supplemental water may be given.

Pruning

Removing spent flowers promotes continued bloom. Deadhead exhausted spikes back to the next bud or basal knot. No fertilizing usually needed, though light feeding during growing season helps. In zones where it grows as an annual, sow seed directly in ground after frost passes. Seeds germinate better with light cold stratification.

Maintenance Calendar

Spring (March-May): Allow seed to germinate if grown as annual, or ensure perennial growth. Water young plants regularly. Summer (June-August): Peak blooming season. Remove spent flowers. Water when dry. Autumn (September-October): Growth slows. Collect seed for next season. Winter (November-February): Dormancy in temperate zones. Minimal care needed.

Winter Hardiness

Scarlet larkspur is semi-hardy. In USDA zones 8-10, it overwinters as a perennial. In zone 7 and colder, grow as an annual or protected plant. Some years in zone 7 are possible with shelter. In Northern Europe (Netherlands, Belgium, France), it grows as a summer bloom from seed or as a year plant. Many garden centers stock seed and young plants.

Companion Plants

Scarlet larkspur fits well in warm, dry gardens with other Californian wildflowers. Combine with Eschscholtzia californica (California poppy), Clarkia, Gaillardia. In sunny places, it grows well with Salvia greggii and Manfreda. Plant in groups for dramatic visual effect. Low-growing groundcover around plants breaks monotony for interesting contrast.

Closing

The Scarlet larkspur is an unparalleled wildflower that adds beauty and drama wherever it grows. With proper placement in warm, sunny, dry climates, enjoy spectacular scarlet-red blooms from May to August. This is the larkspur for gardeners wanting authentic Californian wildflowers.

This plant represents the wild beauty of Western American mountain and desert flora, and brings its elegance to every garden where it can thrive.