Trelease's Larkspur is a rare native delphinium found only in a handful of counties in Missouri's southwestern Ozark region, where it thrives on limestone glades in full sun. This perennial grows 2 to 4 feet tall and produces loose spikes of deep blue to bluish-purple flowers each spring, blooming from May through June with individual blossoms reaching about an inch long. Hardy in zones 5 through 7, it brings a sophisticated coolness to gardens while tolerating heat and humidity better than most delphinium hybrids. The deer leave it alone, and butterflies flock to its showy blooms. For gardeners in the upper Midwest and beyond, this species offers native charm with genuine garden resilience.
Full Sun
Moderate
5-7
48in H x 30in W
—
High
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This rare Missouri native brings deep blue spikes to spring gardens and genuinely shrugs off heat and humidity that would wilt most delphiniums. Unlike the temperamental hybrids many gardeners struggle with, Trelease's Larkspur has proven itself in challenging climates like St. Louis while still thriving in cooler regions. Butterflies adore the flowers, deer pass it by, and if you deadhead spent spikes, you might even coax a sparse second bloom in autumn. The complex, asymmetrical flowers with their distinctive spurred sepals are architectural beauty with a tough backbone.
Trelease's Larkspur is grown for ornamental display in gardens where its tall spikes of spring blooms provide vertical structure and deep blue color. The showy flowers attract butterflies and other pollinators, making it valuable in wildlife gardens. It works well in borders, native plant gardens, and regional landscapes of the Midwest and upper South where its native hardiness shines.
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Trelease's Larkspur may be grown from seed. Start seeds indoors in cool conditions, as delphinium seeds benefit from a period of moist chilling. Sow in a seed-starting mix and keep at 60 to 65 degrees Fahrenheit. Seeds typically germinate in 15 to 25 days. Transplant seedlings into larger containers once they develop true leaves.
Harden off seedlings by gradually exposing them to outdoor conditions over 7 to 10 days. Transplant to the garden after the last frost date when soil has warmed. Space plants 12 to 30 inches apart to accommodate their mature width. Choose a location with full sun and well-drained, rocky limestone soil if possible, with afternoon shade in hot climates.
Seeds may be direct sown in autumn or early spring in zones 5 through 7, pressing them into prepared soil and keeping them consistently moist until germination occurs.
Remove spent flower spikes regularly to encourage additional blooms throughout the season and potentially trigger a sparse second bloom in autumn. Taller plants sometimes need staking or support as they reach their full 2 to 4 foot height, particularly in windy locations. Cut back dead foliage in late fall or early spring as new growth emerges.
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“Delphinium treleasei takes its name from the region where it evolved and where it remains, a living connection to the limestone glades of southwestern Missouri. This species represents the wild genetics that refined delphinium breeders draw from when they chase hardiness and heat tolerance. Its narrow native range makes it genuinely rare in cultivation, and gardeners who grow it participate in preserving a piece of Ozark flora that exists nowhere else in the world.”