Delphiniums, are excellent in borders and great for cutting. If cut when 1/4 of flowers are open , they can last a week in water. Tall Spires Packed with Double Blooms Just Keep on Coming! not difficult to grow, asking only plenty of sun, some protection from wind, and cool temperatures. Plant seeds outdoors in late fall or early spring. (Seeds maybe started indoors 6 to 8 weeks before the last frost.) Delphinium prefers well-drained soil enriched with compost. Sow seeds, cover lightly with soil and keep moist until seedlings are established. Zones 3-7. Ht. 30-36″. Final spacing of mature plants should be 10 inches. NOTE: Seeds/plants harmful if eaten.