Annual
Larkspur
Consolida ajacis · Ranunculaceae
Also called: Rocket Larkspur, Annual Delphinium, Doubtful Knight's Spur
Larkspur (Consolida ajacis) is a low-water annual well suited to Tucson and the low desert. It grows to 1-4 ft tall and 8-12 in wide in full sun.
Larkspur at a glance
- Water use
- Low (established)
- Sun
- Full sun (6+ hours) for tall, sturdy flower spikes; tolerates light afternoon shade.
- Mature size
- 1-4 ft tall and 8-12 in wide
- Growth rate
- Moderate to fast within the cool season
- Bloom
- Blue, purple, violet, pink, white, and lilac, Spring in Tucson (Mar-May).
- Cold hardiness
- Cold-hardy; fall-sown seedlings tolerate Tucson winter frosts and light freezes. Heat-intolerant and dies back by early summer.
- Soil
- Well-drained soil amended with compost; tolerates alkaline desert soil but needs good drainage to avoid crown rot.
- Native range
- Mediterranean / southern Europe. Grown as a cool-season annual in Tucson. (Formerly classified as Delphinium ajacis/Delphinium ambiguum.)
- Best used as
- Cool-season wildflower and cottage beds, Cut and dried flowers, Vertical accent in borders, Pollinator gardens
- Wildlife
- Attracts bees, butterflies, and hummingbirds with its nectar-rich spurred flowers; deer- and rabbit-resistant due to toxicity.
- Toxicity
- Toxic to people, pets, and livestock. All parts (especially seeds and young foliage) contain diterpenoid alkaloids that can cause serious poisoning if ingested; handle seed carefully and keep away from children and animals.
How to grow Larkspur in Tucson & the low desert
Watering
A cool-season annual: direct-sow seed in fall (Oct-Nov) into the spot where it will grow (taproot resents transplanting); cool soil and a brief chill aid germination. Water to establish, then water moderately, letting the surface dry between irrigations. Blooms in spring and finishes as heat arrives.
Fertilizer & nutrients
Light feeder. Compost at planting plus an occasional balanced feeding supports the tall spikes; avoid heavy nitrogen, which weakens stems.
Pruning & care
Deadhead spent spikes to encourage side branching and prolong bloom; stake tall varieties in windy spots. Premier cut flower (fresh or dried).
Notes
A classic Tucson cool-season annual for spring vertical color; direct-sow in fall for spring spikes since the taproot makes transplanting difficult. It self-seeds and naturalizes. Note the toxicity: keep seed and plants away from pets, kids, and grazing animals. Replace/re-sow each season; it cannot survive the low-desert summer.
Sources: University of Arizona Cooperative Extension / Pima County Master Gardeners; Brad Lancaster Sonoran Desert Planting Calendar; Tucson Organic Gardeners Planting Guide