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How to Grow Dwarf Delphinium Summer Series Periwinkle

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Dwarf Delphinium Summer Series Periwinkle

Delphinium grandiflorum

flower

A compact, perennial delphinium cultivar bred specifically for garden performance, reaching 12-18 inches tall with vibrant periwinkle-blue flowers arranged in dense spikes. The Summer Series is known for reliable blooming throughout warm months and improved disease resistance compared to tall delphiniums. This variety is ideal for borders, containers, and cottage gardens.

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Example Dwarf Delphinium Summer Series Periwinkle timeline · Pittsburgh, PA (Zone 6b)

  1. Plant Dwarf Delphinium Summer Series Periwinkle

    Around Apr 17

    Near Pittsburgh's average last spring frost.

  2. Tend & protect

    Late spring–summer

    Watering, feeding, and pest-watch reminders.

  3. First Dwarf Delphinium Summer Series Periwinkle blooms

    Around Jun 16

    ≈ 60 days after planting

Sample dates for Pittsburgh, PA. Sign up to get exact Dwarf Delphinium Summer Series Periwinkle dates for your own zip code.

Growing Conditions

☀️
Sun: Full sun, 6-8 hours daily; afternoon shade helpful in zones 7-8
💧
Water: Consistent moisture, 1-1.5 inches per week; keep soil evenly moist but not waterlogged. Water at soil level to prevent powdery mildew on foliage.
📏
Spacing: 12 inches
📅
Days to maturity: 60-90 days from seed to first bloom
🌱
Planting depth: Surface sow seeds, press lightly into soil; seeds need light to germinate. Transplants set at soil level.

Soil

Type: Well-draining loamy soil, fertile and rich in organic matter
pH: 6.0-7.0
Amendments:
Compost Aged manure Perlite for drainage Peat moss or coconut coir

Growing Zones

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Zones 3-8, thrives in cooler climates with consistent moisture

3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a

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Growth Stages

1

Germination & Seedling

2-3 weeks

Tiny seedlings emerge with true leaves visible within 10-14 days. Very delicate at this stage with fine foliage.

Keep soil consistently moist but not wet. Provide bright indirect light and good air circulation. Avoid damping off by ensuring air movement.

2

Vegetative Growth

3-4 weeks

Plant develops multiple sets of finely divided, ferny foliage. Compact, bushy form begins to establish; 2-4 inches tall.

Pinch back growing tips once when 2-3 inches tall to encourage branching and fuller habit. Begin weekly liquid fertilizer applications (diluted 1:2).

3

Bud Formation & Early Flowering

2-3 weeks

Dense flower spikes emerge from leaf axils with visible flower buds clustered along the spike. First flowers begin opening in periwinkle-blue.

Maintain consistent watering and apply diluted fertilizer every 10-14 days. Deadhead spent flowers as they fade to encourage continuous blooming.

4

Peak Flowering

4-6 weeks

Abundant periwinkle-blue flowers densely packed on spikes, plant reaches 12-18 inches. Multiple spikes bloom simultaneously.

Deadhead regularly to extend bloom season. Provide afternoon shade in hot climates. Watch for powdery mildew; ensure good air circulation.

5

Seed Development & Decline

3-4 weeks

If flowers are not deadheaded, seed pods develop along spikes. Plant energy redirects to seed production, flowering slows.

Continue deadheading to prolong bloom or allow one or two spikes to go to seed if you want to collect seeds. Reduce watering frequency slightly as season cools.

Companion Planting

Plan your garden →

Plant with:

Catmint (Nepeta) Coreopsis Salvia Geranium Lavender Russian Sage Phlox Yarrow

Avoid planting near:

Fennel Anise Dill Plants requiring dry conditions (sedums, sempervivums)

Common Pests

  • Improve air circulation, avoid overhead watering. Apply sulfur dust or neem oil spray every 7-10 days. Space plants adequately.

  • and

    Handpick in early morning or evening. Use beer traps, copper tape barriers, or food-grade diatomaceous earth around plant base.

  • Increase humidity and mist foliage regularly. Apply insecticidal soap or neem oil every 5-7 days if infestation occurs.

  • Spray with strong water stream to dislodge. Use insecticidal soap or neem oil. Introduce beneficial insects like ladybugs.

  • Remove infected leaves immediately. Ensure good air circulation and avoid wetting foliage. Apply copper fungicide if needed.

Uses

🍳

Edible Flowers & Garnish

Culinary

Delphinium flowers are safe for culinary use and provide striking periwinkle color to salads, cakes, and beverages. Use only organically grown flowers free from pesticides and spray. [source]

🎨

Cut Flowers & Floral Arrangements

Craft

Excellent for fresh bouquets and dried flower arrangements. Spikes last 5-7 days in a vase and dry exceptionally well for long-term decorative use. [source]

🏠

Natural Dye Production

Household

Delphinium flowers and leaves produce blue and purple dyes valued in textile and craft projects. The pigments shift from blue to purple depending on mordant used. [source]

🦋

Pollinator Attraction

Wildlife

Blue flowers attract bees, butterflies, and hummingbirds, making this variety excellent for pollinator gardens and supporting local ecosystems. [source]

💊

Traditional Herbal Use

Medicinal

Historically used in traditional medicine for various purposes, though modern use is limited due to toxicity. Consult herbalists before use; generally not recommended for internal consumption. [source]

This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.

Harvest Tips

Delphiniums are ornamental flowers; cut stems when 50-75% of flowers on spike are open for fresh arrangements. Cut in early morning, condition in cool water for 2-4 hours before arranging. For seed collection, allow one or two spikes to mature fully; harvest seed pods when brown and dry, store in cool, dry place. Deadhead spent flowers regularly throughout the season to encourage continuous blooming.

Fun Facts

  • 🌱 The name 'delphinium' comes from the Greek word 'delphin' (dolphin) because the flower's shape resembles a dolphin's nose. Medieval gardeners believed the flowers attracted dolphins!
  • 🌱 The Summer Series was specifically developed by breeders to overcome the common problem of tall delphiniums requiring staking and tending—these dwarf versions stand independently and rebloom reliably all season.
  • 🌱 Delphinium seeds can remain viable for 3-4 years when stored properly in cool, dry conditions, making seed saving from one season highly successful for the next year's garden.

Gardening Terms

New to gardening? Learn about terms used in this guide:

Cultivar Damping Off Deadhead Full Sun Perennial pH Pinch Back True Leaves
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