Families of Trees
Botanically, Broadleaf trees are classed as Angiosperms. Angio comes from the Greek for “vessel”. So an Angiosperm has its seeds in a vessel, in this case an ovary. Broadleaf trees generally have wide leaves with veins. Broadleaf trees bear flowers and fruits, not cones. Wood from Broadleaf trees is called Hardwood. Oak, Beech, Walnut, Lime, Poplar, Sycamore and Ash are all European hardwoods used in furniture manufacture.
Conifers are classed as Gymnosperms because they have “naked seeds” which are not surrounded by an ovary. Gymno comes from the Greek for “naked”. Conifers have leaves that are needle-like or scale-like. They bear pollen and seed cones, not flowers and fruit. The word “Conifer” means cone-bearing. Wood from Conifers is called Softwood. Pine, Spruce, Cedar and Cypress are softwoods used in furniture manufacture. Only three conifers grow naturally in Britain – Scots Pine, Common Juniper and Yew. All the others have been introduced.
The Ginkgo, also known as the Maidenhair, is a Gymnosperm but is strictly not a Conifer. It has catkin-like pollen cones like a Conifer but does not produce seed cones. Its seeds develop into round green fruits on the end of stalks. The fertilization process involves motile sperm, a feature of Mosses, Liverworts and Ferns. Hence it is in a botanical class of its own and is often referred to as a “living fossil”.
In the Field Guide to Trees of Britain and Europe the families and genera are arranged according to the linear sequences published by Christenhusz et al. (2011) for Gymnosperms and by Haston et al. (2009) for Angiosperms. Botanical institutions organize their collections in linear sequences that reflect evolutionary relationships, rather than arranging them alphabetically. Various linear sequences have been proposed over the years but these sequences, based increasingly on DNA analysis, are now considered to be the most reliable. Note that since the sequence is generated from an evolutionary tree, the closer in the sequence the families are, the more they should have similarities.
A simplified list of some families and common trees in their correct order is shown below. Note that in the latest publications, Maples and Horse Chestnuts are now part of an expanded Soapberry family (Sapindaceae). In the conifer table the term Cypress includes the genera Cupressus and ChamaecyparIs and Sequoia includes the Coast Redwood, Dawn Redwood and Giant Sequoia.