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Dahlia cultivar

Dahlia 'Penhill Watermelon'

Decorative; giant ‘dinnerplate’ · Maritz, 2000, South Africa

V Written by Editorial Team · Updated January 2026

Dahlia ‘Penhill Watermelon’ is a giant decorative dahlia with ruffled pink to watermelon‑rose blooms that can show cream and lavender tones. It prefers full sun and rich, well‑drained soil. It blooms from midsummer to frost in most North American gardens. The very large flowers make a strong focal point and can be cut with careful support. Plants are tall and need staking in open sites. The tubers are frost‑tender and require winter protection where winters are cold.

Dahlia 'Penhill Watermelon'
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Penhill Watermelon

Decorative; giant ‘dinnerplate’ · Maritz, 2000, South Africa

At‑a‑glance

  • Group/Class: Decorative; giant ‘dinnerplate’
  • Height × spread: 5-6 ft × 2-3 ft (1.5-1.8 m × 60-90 cm)
  • Bloom window: mid‑summer to frost
  • Color & flower form: pink to watermelon with cream and lavender tints; very large, ruffled double decorative
  • Fragrance: 0 none
  • USDA hardiness: grown as annual in most regions; may overwinter in ground in Zone 7 to 10 where soils are well‑drained
  • Breeder / Year / Origin: Maritz, 2000, South Africa
  • Cut‑flower notes: very large heads; long stems; typical vase life 3 to 5 days when cut at early maturity.
  • Pet safety: avoid

How it differs

  • Extra‑tall habit compared with many dahlias.
  • Ruffled petals and shifting pink tones unlike standard decorative forms.
  • Needs strong staking because of flower size and height.

Strengths

  • Dramatic, oversize blooms for late‑season impact.
  • Good stem length for large arrangements.
  • Reliable display into frost with deadheading.

Care in one minute

Site: full sun; deep, fertile, well‑drained soil; neutral pH.

Water: keep evenly moist; avoid waterlogging.

Feeding: moderate feeding; avoid high nitrogen once buds develop.

Training: pinch once at 18 in; stake with multiple ties; deadhead consistently.

Overwintering: lift after frost and store around 40 to 45°F (4 to 7°C), or mulch and risk in‑ground only in mild, well‑drained Zone 7 to 10 locations.

Watch‑outs

  • Can flop without sturdy staking and ties.
  • Blooms may shatter in heavy rain or wind.
  • Frost‑tender tubers require storage outside mild zones.

Best uses (tags)

  • cutting
  • borders
  • late season

Provenance note

Bred by Maritz in South Africa and introduced in 2000; widely grown for show‑sized flowers.

References

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Written by: Your Flowers Guide editorial team
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