Rhododendron 'Hugh Koster'

Large hybrid rhododendron

  • Flowering Time : May, June
  • Height in 10 years : 3 metres / 9 feet 10 inches


Upright and spreading with grooved leaves. Mid green leaves. Bright crimson flowers with lighter centres are held in an upright cylindrical firm trusses, .(M.Koster & Son 1915)

Flower Months

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Rhododendrons will start flowering around this time, depending on the season, for a week or so.


  • UK Zone : 4
  • RHS Zone : H (Fully Hardy)
  • EGF Zone : H2
  • US Zone : 7A
  • Min Temp : -18°C (0°F)

Hardy in all but the coldest parts of Pacific Northwest and UK, France and northern Italy, around Bergen (Norway) and mildest parts of NE USA such as Cape Cod and parts of Long Island.

Alternative Rhododendrons

  • Rhododendron 'Kluis Sensation'
  • Rhododendron 'Robert Croux'
  • Rhododendron 'Souvenir de D. A. Koster'