How to Grow Pacific Giants Delphinium
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Pacific Giants Delphinium
Delphinium × cultorum 'Pacific Giants'
flowerPacific Giants delphiniums are stunning hybrid flowers known for their towering spikes of densely-packed blooms in shades of blue, purple, pink, and white. These majestic perennials can reach 4-6 feet tall and create dramatic vertical interest in garden borders. They are prized by florists and gardeners for their impressive flower spikes and long vase life.
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Example Pacific Giants Delphinium timeline · Pittsburgh, PA (Zone 6b)
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Plant Pacific Giants Delphinium
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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First Pacific Giants Delphinium blooms
Around Jul 16≈ 90 days after planting
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Growing Conditions
Soil
Growing Zones
Find your zone →Thrives best in zones 3-7; tolerates zone 8 in cool climates with afternoon shade
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Seedling
3-4 weeksTiny seedlings with first true leaves appearing 10-14 days after germination. Plants are delicate and require consistent moisture and gentle light.
Maintain 65-70°F temperature; provide bright, indirect light; thin seedlings to prevent damping-off disease; avoid overwatering
Vegetative Growth
6-8 weeksYoung plants develop deeply-lobed foliage and establish a strong root system. Stems become sturdy and woody at the base; plant height increases rapidly.
Gradually harden off transplants before moving outdoors; stake or support emerging stems; pinch tops to encourage bushier growth with multiple flower spikes (optional, reduces height slightly); fertilize biweekly with balanced fertilizer
Budding and Flowering
4-6 weeks per spikeDistinctive flower spikes develop with densely-packed florets from bottom to top. Initial flowers at base open while upper buds continue developing. Full spike displays hundreds of individual blooms.
Provide sturdy staking or support; deadhead spent flowers from base upward to encourage continued blooming; water consistently; apply liquid fertilizer weekly to support heavy flowering; watch for powdery mildew and increase air circulation
Seed Development
3-4 weeksIf flowers are not deadheaded, seed pods (follicles) develop along the spike, turning brown as they mature and dry. Seeds remain viable when fully dried.
Allow selected spikes to mature if collecting seeds; cut seed heads when brown and dry; store seeds in cool, dry place; self-seeding may occur but seedlings may not match parent plant color
Dormancy
4-6 months (winter)After first frost or at end of growing season, foliage dies back completely. Plant enters winter rest period with only the woody crown visible at soil level.
Cut back dead foliage after frost; apply light mulch (2-3 inches) for winter protection in cold zones; reduce watering significantly; ensure excellent drainage to prevent crown rot during wet winters
Common Pests
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Monitor for sawdust-like frass and wilting stems; remove and destroy affected stems; apply spinosad in late spring
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and
(Limax and Helix species)
Hand-pick especially at night; use beer traps or copper barriers; apply diatomaceous earth around base; encourage natural predators
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Improve air circulation by thinning foliage and avoiding overhead watering; apply sulfur dust or neem oil weekly starting in mid-summer; plant in full sun
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Remove severely infested shoots; spray with insecticidal soap or sulfur; maintain humidity below 60% by improving air circulation
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and
(Pythium and Phytophthora species)
Ensure excellent drainage and avoid waterlogging; do not overwater; remove and discard affected plants; prevent by not planting in low-lying areas
Uses
Edible Flower Garnish
CulinaryIndividual delphinium flowers can be candied and used to decorate cakes and desserts, or floated in beverages and cocktails. Ensure the plant has not been treated with pesticides before use. [source]
Cut Flower Arranging and Floristry
CraftPacific Giants are prized by professional florists for their tall, dramatic spikes that add height and structure to wedding bouquets, funeral arrangements, and formal displays. Their long vase life makes them excellent for fresh arrangements. [source]
Garden Design and Landscape Focal Point
HouseholdThese towering flowers create stunning vertical accents in herbaceous borders, cottage gardens, and perennial beds. They work well in color-themed gardens and add height to the back of borders for dramatic layered displays. [source]
Traditional Herbal Medicine
MedicinalHistorically, delphinium species have been used in traditional medicine for various ailments, though modern use is limited due to the plant's toxic properties. All parts contain alkaloids and should not be ingested without professional guidance. [source]
Pollinator Attraction
WildlifePacific Giants attract bees, hummingbirds, and butterflies with their abundant nectar, making them valuable for supporting pollinator populations in the garden. [source]
This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.
Harvest Tips
Cut flower spikes when the bottom third to half of the flowers are fully open for longest vase life (7-10 days). Cut in early morning with sharp, clean pruners. For arrangements, re-cut stems underwater and change water every 2-3 days. Remove lower foliage from stems. For seeds, allow spikes to dry on plant, then collect brown seed pods and store dry in cool conditions for next season.
Fun Facts
- 🌱 Pacific Giants delphiniums can produce multiple flower spikes from a single plant if the first spike is deadheaded; gardeners can enjoy continuous blooms throughout the season by removing spent flowers
- 🌱 The name 'delphinium' comes from the Greek word 'delphin' meaning dolphin, as the unopened flower buds resemble a dolphin's nose
- 🌱 Some delphinium varieties are said to repel slugs naturally, and their tall stature makes them useful companion plants for shorter vegetables and ornamentals that need protection from garden pests
Gardening Terms
New to gardening? Learn about terms used in this guide:
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