This section is from the book "Commercial Gardening Vol4", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
The Common British Hazel or Filbert (C. Avellana) grows to a height of 20 ft. or more, and is highly valued. It has several varieties, including purpurea, with rich-purple leaves; aurea, golden; heterophylla or laciniata, deeply cut; and pendula, weeping. The common kind is easily raised from seeds, and the varieties are grafted on it, or are layered. C. Colurna, 30-60 ft., from Asia Minor, grows well in parts of the British Islands. It has whitish flaky bark, and roundish heart-shaped leaves.