← Plant Guides

How to Grow Beauty of Cobham

Wikimedia Commons

Beauty of Cobham

Dahlia × pinnata 'Beauty of Cobham'

flower

Beauty of Cobham is a classic decorative dahlia cultivar known for its stunning bicolor blooms featuring white petals with pink or mauve edges and tips. This heirloom variety produces abundant, long-lasting flowers on strong stems ideal for cutting and garden display. It is a mid-season dahlia that brings elegant, romantic color to late summer and fall gardens.

When should you plant Beauty of Cobham in your zone?

Get a personalized planting timeline — when to start seeds, transplant, and harvest — based on your USDA zone and local frost dates. Free to start.

Get my Beauty of Cobham timeline →

Example Beauty of Cobham timeline · Pittsburgh, PA (Zone 6b)

  1. Plant Beauty of Cobham

    Around Apr 17

    Near Pittsburgh's average last spring frost.

  2. Tend & protect

    Late spring–summer

    Watering, feeding, and pest-watch reminders.

  3. First Beauty of Cobham blooms

    Around Jul 16

    ≈ 90 days after planting

Sample dates for Pittsburgh, PA. Sign up to get exact Beauty of Cobham dates for your own zip code.

Growing Conditions

☀️
Sun: Full sun, 6-8 hours daily minimum (8+ hours preferred for maximum blooms)
💧
Water: Water deeply and consistently, maintaining evenly moist but not waterlogged soil. Water at soil level to avoid wetting foliage. Reduce watering in cool, wet weather to prevent root rot. Dahlias are moderately drought-tolerant once established but bloom more prolifically with regular moisture.
📏
Spacing: 24 inches
📅
Days to maturity: 90-120 days from planting tubers or transplants to first blooms
🌱
Planting depth: 4-6 inches for tubers; plant transplants at same depth as nursery container

Soil

Type: Well-draining loamy soil rich in organic matter
pH: 6.0-7.0
Amendments:
Compost or aged manure Peat moss or coconut coir Perlite for drainage Balanced fertilizer (5-10-10)

Growing Zones

Find your zone →

Thrives in zones 4-9; grown as an annual in zone 3 or tender perennial in zones 8-10

3b 4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a 9b 10a

Sign up free to see if Beauty of Cobham grows in your zone — and get a personalized planting timeline.

Get my Beauty of Cobham timeline →

Growth Stages

1

Tuber Sprouting & Root Development

2-3 weeks

Dormant tubers develop sprouts and white roots. No visible above-ground growth yet.

Plant tubers horizontally 4-6 inches deep in warm soil (60°F+). Keep soil lightly moist but not soggy. Provide support structure nearby as plants establish.

2

Vegetative Growth

4-6 weeks

Stems emerge and grow rapidly. Foliage is dark green and lush. Plant develops bushy form with increasing stem branching.

Water regularly and provide consistent moisture. Pinch out top growth when plant reaches 12-15 inches to encourage bushiness and more flower production. Support stems with stakes or cages. Begin fertilizing every 2 weeks with balanced fertilizer.

3

Bud Formation & Budding

2-3 weeks

Flower buds appear at stem tips. Buds are tightly formed and show distinctive dahlia bud shape.

Continue regular watering and feeding. Remove bottom leaves as plant grows to improve air circulation. Disbud side buds if large exhibition blooms are desired, leaving only terminal bud per stem. Stake and tie stems if needed.

4

Flowering & Blooming

8-12 weeks (until frost)

Distinctive bicolor flowers open with white petals and pink/mauve edges. Blooms are full, decorative form with many layered petals. Flowers last 7-10 days on plant.

Deadhead spent flowers regularly to encourage continued blooming. Keep cutting for bouquets; this stimulates more flower production. Maintain consistent watering. Watch for pest damage and treat promptly. Continue fertilizing every 2-3 weeks with higher phosphorus formula (e.g., 5-10-10).

5

Fall & Dormancy Preparation

4-6 weeks before frost

Foliage begins to yellow and decline as temperatures cool and frost approaches. Tubers underground mature and harden.

Reduce watering as growth slows. In zones 3-7, dig tubers after first light frost (32°F) kills foliage. Clean, dry, and store tubers in cool (50-55°F), dry location with sawdust, peat moss, or perlite. In zones 8-10, mulch heavily and leave in ground or dig for storage and replanting.

Companion Planting

Plan your garden →

Plant with:

Salvia Coreopsis Rudbeckia Zinnias Sedum Russian sage Lavender Echinacea Black-eyed Susan Cosmos

Avoid planting near:

Fennel Dill Potatoes Tomatoes (disease susceptibility)

Common Pests

  • Spray with water to dislodge. Use insecticidal soap or neem oil. Improve air circulation to prevent infestations.

  • Spray with strong water stream. Use insecticidal soap, neem oil, or horticultural oil. Introduce ladybugs or lacewings.

  • Remove affected flower buds and blooms. Use yellow sticky traps. Spray with neem oil or insecticidal soap.

  • and

    Hand-pick in early morning or evening. Use slug bait, copper tape barriers, or diatomaceous earth. Create beer traps.

  • Hand-pick early in morning when beetles are sluggish. Use beetle traps away from dahlia planting. Apply neem oil or spinosad.

  • Improve air circulation by spacing plants properly and removing lower leaves. Spray with sulfur or potassium bicarbonate. Remove infected foliage.

  • Reduce humidity and improve air circulation. Remove and discard infected flowers and foliage. Avoid overhead watering. Apply fungicide in wet weather.

Uses

🍳

Edible Flowers for Decoration

Culinary

Dahlia petals are edible and can be used as garnishes for desserts, salads, and cocktails, adding elegant visual appeal and a slightly peppery, herb-like flavor. [source]

🏠

Cut Flower Arranging

Household

Beauty of Cobham is an excellent cut flower for floral arrangements, wedding bouquets, and garden displays due to its long stems, abundant blooms, and distinctive bicolor form. [source]

🏠

Garden Ornament & Focal Point

Household

The plant's profuse, showy blooms and attractive foliage make it an ideal focal point or accent plant in mixed perennial borders, cutting gardens, and formal garden designs. [source]

🦋

Pollinator Support

Wildlife

Dahlias attract bees, butterflies, and other beneficial pollinators throughout the growing season, supporting local pollinator populations and promoting garden biodiversity. [source]

🎨

Dried Flowers & Craft

Craft

Dahlia blooms can be dried and used in floral crafts, wreaths, and dried arrangements. Dry flower heads by hanging upside down in a warm, dark location for 2-3 weeks. [source]

Harvest Tips

Cut flowers in early morning or evening when stems are most hydrated. Cut long stems at a 45-degree angle, removing lower foliage. Immediately place in cool water with floral food. Flowers last 7-10 days in a vase. For maximum vase life, re-cut stems daily and change water every 2-3 days. Cut frequently to encourage more bloom production throughout the season.

Fun Facts

  • 🌱 Beauty of Cobham is an heirloom dahlia variety dating back to the mid-20th century, originating from Cobham in Surrey, England, and remains a beloved choice for historic and cottage gardens.
  • 🌱 Dahlias are native to Mexico and were called 'water pipe flower' by the Aztecs due to their hollow stems. The genus name 'Dahlia' honors Swedish botanist Anders Dahl.
  • 🌱 Dahlia tubers can be divided to create multiple new plants; each tuber section must have at least one 'eye' or growth point to successfully sprout and grow.

Gardening Terms

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

Cultivar Deadhead Full Sun Heirloom Mulch pH
Shop Beauty of Cobham plants and related plants at Plant Addicts →

Join 30,000 gardeners planning their gardens with LizPlants.

Get your personalized Beauty of Cobham planting timeline

Tell us your zip code and we'll calculate exactly when to start Beauty of Cobham seeds, transplant seedlings, and harvest — based on your USDA zone and local frost dates. Includes calendar reminders and printable task lists. Free to start.

Get my Beauty of Cobham timeline →