How to Grow Delphiniums: A Complete Care Guide

Delphiniums, with their towering spires of vibrant blooms, bring vertical drama and cottage garden charm to any landscape. These stately perennials offer some of the truest blue flowers in the garden palette, along with purples, pinks, and whites that create a stunning backdrop for summer gardens. While they have a reputation for being somewhat demanding, with the right care techniques, even beginning gardeners can successfully grow these magnificent plants.

Quick Facts

Feature	Details
Hardiness	Zones 3-7 [What’s My Zone?]
Heat Zones	Struggles in zones above 7
Climate Zones	Best in cool, temperate climates
Plant Type	Perennial
Plant Family	Ranunculaceae
Genus	Delphinium
Common Names	Larkspur (though true larkspur is Consolida)
Exposure	Full sun to partial shade
Season of Interest	Early to mid-summer
Height	3-6 ft (dwarf varieties 1-2 ft)
Spread	1-2 ft
Maintenance	High
Water Needs	Medium to high
Soil Type	Rich, well-draining
Soil pH	Neutral to slightly alkaline (6.5-7.5)
Soil Drainage	Well-draining, consistent moisture
Characteristics	Tall flower spikes, deeply lobed foliage
Attracts	Bees, butterflies, hummingbirds
Garden Uses	Back of borders, cottage gardens, cutting gardens
Garden Styles	Cottage, English, Traditional

Why Grow Delphiniums?

Delphiniums offer gardeners the rare gift of true blue flowers, a color that’s surprisingly uncommon in the plant world. Their dramatic height creates a magnificent backdrop for other garden plants, and their stately presence adds a touch of English garden elegance to any landscape. Beyond their beauty, delphiniums attract beneficial pollinators like bees and butterflies, supporting local ecosystems while providing weeks of spectacular blooms.

Where Will Delphiniums Thrive?

Perfect For:

✅ Cool Climate Gardens – Delphiniums flourish in regions with cool summers and mild winters, making them stars of northern gardens.
✅ Cottage-Style Landscapes – Their traditional character and vertical form create the quintessential cottage garden look.
✅ Cutting Gardens – The tall flower spikes make exceptional cut flowers, lasting up to a week in arrangements.

Not Suitable For:

🚫 Hot, Humid Climates – Delphiniums struggle in areas with hot, humid summers (zones 8+).
🚫 Windy, Exposed Sites – Their tall stems can snap easily without protection from wind.
🚫 Poorly Drained Soils – Root rot quickly develops in soggy conditions.

Planting Guide

When to Plant

Best planting time is early spring or early fall when temperatures are cool. In hot summer regions, fall planting is preferable to give roots time to establish before summer heat arrives.

What You’ll Need

✅ Rich, well-draining soil or quality potting mix
✅ Compost or well-rotted manure
✅ Bone meal or phosphorus-rich fertilizer
✅ Sturdy stakes or plant supports
✅ Slug and snail deterrents
✅ Lime (if soil is acidic)

Step-by-Step Process

From Seed:

Start seeds indoors 8-10 weeks before last frost, or direct sow in fall for cold stratification.
Press seeds lightly into soil surface – they need light to germinate.
Keep soil consistently moist but not soggy at 65-70°F.
Germination occurs in 14-21 days; be patient as germination can be erratic.
Transplant seedlings when they have several true leaves.

From Transplants:

Prepare soil by incorporating 2-3 inches of compost and a handful of bone meal per plant.
Dig a hole twice as wide as the root ball and at the same depth.
Place plant so the crown (where stems meet roots) is at soil level.
Backfill with soil, firm gently, and water thoroughly.
Space plants 18-24 inches apart to allow for good air circulation.

💡 Adaptation Tip: For gardeners with limited mobility, consider growing dwarf varieties like the ‘Magic Fountains’ series, which reach only 2-3 feet tall and require less staking and maintenance.

Essential Care

Water

💧 Consistent moisture is crucial, especially during the growing season. Water deeply when the top inch of soil feels dry, typically 1-2 times per week depending on climate. Never allow soil to dry out completely, but avoid waterlogged conditions which lead to root rot.

Sunlight

☀️ Delphiniums need 6+ hours of sun in cool climates. In warmer regions (zones 6-7), provide afternoon shade to prevent heat stress and extend the blooming period. Morning sun with afternoon shade offers the ideal balance in these areas.

Soil & Feeding

🌱 These are heavy feeders that thrive in rich, well-draining soil with plenty of organic matter. Apply a balanced, slow-release fertilizer in spring when new growth appears, followed by liquid fertilizer every 2-3 weeks during the growing season. A pH of 6.5-7.5 is ideal; add lime if your soil is acidic.

Seasonal Care

🌱 Spring

Apply compost around plants as new growth emerges
Set stakes or supports in place early before plants get tall
Apply slug deterrents before damage occurs
Thin crowded stems to improve air circulation
Fertilize when growth is about 6 inches tall

☀️ Summer

Water consistently during dry spells
Cut primary flower stalks back after blooming to encourage a second flush
Watch for powdery mildew in humid conditions
Continue feeding with liquid fertilizer through blooming period
Provide afternoon shade during extreme heat

🍂 Fall

Cut stems to about 2 inches above ground after first frost
Apply a light mulch of compost around the crown
Divide overcrowded plants (3-4 years old) in early fall
Plant new delphiniums for next year’s display

❄️ Winter

Apply a loose mulch of straw or evergreen boughs after ground freezes to prevent frost heaving
Remove mulch gradually in spring as new growth appears
In zones 3-4, provide extra winter protection with a deeper mulch layer

Problem-Solving

Problem	Likely Cause	Solution
Yellowing leaves	Overwatering or poor drainage	Improve drainage, reduce watering frequency
Powdery white coating on leaves	Powdery mildew	Improve air circulation, apply fungicide, avoid overhead watering
Plants flop over	Insufficient support or too much shade	Install stakes early, move to sunnier location
Few or no flowers	Insufficient sun or nutrients	Move to sunnier spot, increase feeding
Holes in leaves, damaged stems	Slugs and snails	Apply slug bait or barriers, hand pick at night
Black spots on leaves	Bacterial or fungal disease	Remove affected foliage, improve air circulation

Working With Nature

Delphiniums are pollinator powerhouses, attracting a diverse range of beneficial insects. Their nectar-rich flowers support at least 12 species of native bees and numerous butterfly species. The tall, hollow stems can provide nesting sites for beneficial insects when left standing through winter.

For sustainability-minded gardeners, delphiniums form effective partnerships with shallow-rooted plants like catmint or hardy geraniums, which help shade the soil while the delphinium’s deeper roots access nutrients and moisture from lower soil layers.

Reader Success Stories

📖 “I always thought delphiniums were too fussy for my garden, but after following your staking and feeding advice, I now have gorgeous 5-foot spires that are the envy of my neighborhood!” – Martha, Minnesota

📖 “Living in zone 7, I struggled with delphiniums until I planted them where they get morning sun and afternoon shade. Now they bloom twice each summer!” – James, Virginia

Growing Beyond

🌿 Try These Companion Plants:

Shasta Daisies (Leucanthemum × superbum)
Lady’s Mantle (Alchemilla mollis)
Coral Bells (Heuchera spp.)
Rose Campion (Lychnis coronaria)
Foxgloves (Digitalis purpurea)

Frequently Asked Questions:

Q: Can I grow delphiniums in containers?
A: Yes, dwarf varieties work well in large, deep containers with excellent drainage. Use a rich potting mix and be vigilant about watering.

Q: Why are my delphiniums short-lived?
A: These plants are often short-lived perennials (3-4 years). Extend their lifespan by dividing regularly, providing excellent drainage, and protecting from extreme heat.

Q: Should I deadhead my delphiniums?
A: Yes, removing spent flowers prevents seed formation and encourages a second, smaller bloom in late summer.

🌱 Have questions? Join our community forum for more growing tips!