Seeds Delphinium vinescens or Prairie larkspur is a slender, erect perennial, unbranched or branched near the ground to form a clump 1-3 ft. tall. A terminal spike of white, spurred flowers, tinged purple, grows well above the mostly basal, deeply cleft leaves. Pretty spikes of whitish blossoms are on this uncommon wildflower. This perennial cousin of the annual delphinium typically grows in drylands of the American Plains but is happy to be grown in average garden soil too.Hardy in zones 5a-9a.