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Dahlia cultivar

Dahlia 'Thomas Edison'

Informal Decorative · Dahliadel, 1929, USA

V Written by Editorial Team · Updated January 2026

Dahlia ‘Thomas Edison’ is an heirloom informal decorative dahlia with rich purple flowers. It grows best in full sun with fertile, well‑drained soil. It starts blooming by mid to late summer and continues to frost. The blooms show saturated purple that holds well in arrangements. Plants are medium to tall and benefit from pinching and staking. Like all dahlias, it is frost‑tender and needs winter protection outside mild zones.

Single purple pompom dahlia in full bloom against a dark blurred garden background
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Thomas Edison

Informal Decorative · Dahliadel, 1929, USA

At‑a‑glance

  • Group/Class: Informal Decorative
  • Height × spread: 3-4 ft × 1.5-2 ft (0.9-1.2 m × 45-60 cm)
  • Bloom window: mid‑summer to frost
  • Color & flower form: deep purple; double informal 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: Dahliadel, 1929, USA
  • Cut‑flower notes: good stem length; typical vase life 4 to 6 days with clean cuts and cool storage.
  • Pet safety: avoid

How it differs

  • Distinct, saturated purple compared with many garden dahlias.
  • Earlier to flower than many giant dinnerplate types.
  • Moderate plant height eases staking compared with the tallest cultivars.

Strengths

  • Heirloom cultivar with proven garden performance.
  • Useful, long stems for cutting.
  • Reliable flowering from mid‑summer to frost.

Watch‑outs

  • Stems can lean in storms without support.
  • Flower color can read darker in low light.
  • Frost‑tender tubers require storage outside mild zones.

Best uses (tags)

  • cutting
  • borders
  • late season

Care in one minute

Site: full sun; fertile, moisture‑retentive but well‑drained soil; pH near 6.5 to 7.0.

Water: consistent moisture; avoid waterlogged soils.

Feeding: moderate fertilizer; avoid high nitrogen after buds form.

Training: pinch once at 12 to 18 in; stake and tie; deadhead to extend bloom.

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

Provenance note

Introduced to horticulture in 1929 by Dahliadel in the United States.

References

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Single purple pompom dahlia in full bloom against a dark blurred garden background

Dahlia 'Thomas Edison'

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Written by: Your Flowers Guide editorial team
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