Delphinium Growing Guide
Delphinium is a great next step in your growing journey. Follow this guide from planting to harvest and you'll do great.
At a Glance
Difficulty
Moderate
Category
Flower
Sun Exposure
Full Sun
Frost Tolerance
Frost Hardy
Cold Hardiness
Survives to -34°C
Plant Family
Ranunculaceae
Growing Season
Cool Season
Plant Lifecycle
Perennial
Also grows well as
How to Start It
★ Recommended for beginners
Take cuttings of the solid young shoots from the base in spring (hollow ones won't root) — the best way to keep a named variety true.
The aristocrat of the cottage border: towering spires of (often blue) flowers in early summer. Two things to know — they MUST be staked early, as the tall hollow stems snap in wind and rain; and slugs adore the emerging spring shoots, so protect them from day one. Cut the spent spike right down and you'll often get a second, shorter flush in late summer. Short-lived, so propagate to keep them going. All parts are toxic if eaten.
When To Start
First Chance to Plant
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Last Chance to Plant
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When should you plant Delphinium?
Your planting dates depend on your local climate. Sign up and add your location to unlock personalized dates.
Your Delphinium Planting Window
Start planting
May 15, 2026
Last chance
Sep 10, 2026
The Journey Ahead
Delphinium's Lifecycle
Seedling
Mature Plant
Seed Production
Step 1
Prepare Your Space
50 cm
Plant Spacing
30 cm
Row Spacing
Vertical Growing
No.
Succession Planting
No.
Good Companions
Bad Companions
Step 2
Planting & Sprouting
Growing Tips
- 1Give delphiniums full sun, rich moist soil, shelter from strong wind, and staking from the start — that's the recipe for those famous spires.
- 2Guard the spring shoots from slugs religiously (they can strip a plant overnight).
- 3Thin congested clumps to the strongest few shoots for better spikes.
- 4They're short-lived perennials, so divide or take cuttings regularly to keep a supply.
Seedling Phase
Step 3
Growth & Maturity
150 cm
Mature Height
50 cm
Mature Width
Pests to Watch For
Diseases to Watch For
Mature Plant
Step 4
Harvesting
When to Pick
Spires bloom early summer; cut the spent stalk for a second autumn flush
How to Harvest
- 1Stake each spire individually before it gets tall — once it flops or snaps, there's no fixing it.
- 2For cutting, take spikes when about a third to half the florets are open.
- 3After the first flush, cut the flowered stem right back to the base and feed and water well to coax a second, smaller flush in late summer/autumn.
- 4Cut everything down after frost.
Step 5
Saving Seeds
Seed Production
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