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 members of this genus are usually known either as Abies or Picea. The best known are the Hemlock Spruce (T. canadensis), 70-110 ft. in a native state, with feathery branches. There are several varieties. Prince Albert's Spruce (T. Mertensiana), a graceful tree; and T. Pattoniana, all from North America; and T. Sieboldi, from Japan. The Tsugas are recognized by the silvery whiteness on the under surface of the leaves.