Giant Imperial
Also known as: Delphinium sp 'Giant Imperial' · Giant Imperial Larkspur
Severely poisonous
What's special about Giant Imperial
Tall, densely flowered spires in mixed blues, pinks, and whites.
Growing this variety
Giant Imperial follows the same growing basics as Delphinium. Variety-specific maturity above; everything else below applies to the whole Delphinium family.
Germination
Spacing & depth
How to plant
Chill seed 2 weeks in the fridge before sowing. Sow into moist mix, cover lightly, keep 55–60°F. Stake tall spires; cut back after first bloom for a second flush.
Pre-sow treatment
2 weeks moist-cold in the refrigerator before sowing.
Grower's tip
Iconic cottage-garden spire. All parts toxic — keep from livestock and small children.
Good to know before you grow this
Parts of this plant are toxic to people and pets — don't eat it and keep it away from children and animals.
Soil preferences
Well-drained garden soil. Native/wildflower species prefer lean soil; cutting flowers prefer richer beds.
6.0–7.0
Work 1 in of compost into beds before sowing. Skip nitrogen fertilizer on wildflowers — it favors foliage over blooms.
Watering
1 in per week during establishment, drought-tolerant once rooted for most species.
Deep, infrequent soakings at the base. Overhead water on ornamentals promotes botrytis and rust.
Overwatered: rotted crowns, mildew, floppy stems. Underwatered: small blooms, curled leaves, quick fade.
Prefers top-watering — Top-water at the base in the morning. Overhead water batters open flowers and spreads botrytis on tightly-packed blooms.
Temperature tolerance
60–80°F (16–27°C) ideal for most annuals
50–65°F (10–18°C)
Cool-season annuals (larkspur, poppy, snapdragon) tolerate light frost; warm-season annuals (zinnia, cosmos, marigold) are frost-tender.
Container growing
Possible with the right cultivar
8–14 in (20–35 cm) wide
Compact and dwarf types do best in pots; tall cutting flowers need staking.
Detailed harvesting
Nothing here is harvested for the kitchen. Wear gloves for any cutting or deadheading, keep the sap off your skin and eyes, and wash your hands and tools afterwards.
Post-harvest storage & preservation
Do not dry, store or preserve any part of this plant near food. Bag prunings for the bin — never compost them where animals browse, and never burn them.
Culinary, medicinal & other uses
Ornamental only — this plant is poisonous and has no food, tea or home-remedy use. Grow it for looks, wear gloves, and keep it away from children, pets and livestock.
Medicinal or traditional uses are shared for interest only — this is not medical advice. Consult a qualified professional before using any plant medicinally.
Seed saving
Mostly insect-pollinated (outcrossing).
For pure strains, isolate 150–800 ft or bag heads. Wildflower mixes are meant to cross freely.
Stop deadheading favorite blooms; let heads dry brown and rattling on the stem, then collect into a paper bag.
Your zone's planting calendar
Pick your USDA hardiness zone and we'll estimate the key dates for delphinium in your area. These are regional averages — always check your own last-frost forecast before sowing.
My Giant Imperial Delphinium notes
Giant Imperial Delphinium seeds on hand
Track packets and loose seeds you already have. Private to your account.
Par level — leave at 0 for no alert. Anything below par shows on Seed Starting and your shopping list.
Order more seeds
Running low? Reorder from one of these seed stores.
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