Identifying tree types

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Identifying tree types

Atlas cedar Cedrus atlantica © Ita McCobb

There are an estimated 100,000 subspecies of tree worldwide, which means that trees could make up an amazing 25% of all living plant species.

Given that there are so many subspecies of tree and so many different tree families, it is not surprising that the confident identification of a specific subspecies can seem complicated. There are several things that you need to note in order to identify a species. Generally: Do you know how old the tree is? If not, take a note of the diameter of its trunk, then ask yourself, “Will it grow much larger?”

All the following illustrations are meant as examples only and by no means constitute a comprehensive list.

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Tree shapes

Tree shapes © Plant-ark

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Tree bark

Tree bark images © Ita McCobb & Jennifer Hope-Morley

Is it rough or smooth? What colour(s) is it? Is there an aroma if you scratch the wood? If so what does it smell like?

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Tree leaves

Tree leaves images © Ita McCobb

How big is its average leaf? What shape are they? What shape are their margins (edges)? Are they hairy? If so where – above the leaf, below, along the veins, on the stalk or under the main vein joints? What colour is the leaf’s underside? How evident are the leaf veins?

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Tree flowers

Tree flower images © Ita McCobb & Jennifer Hope-Morley

Does the tree produce flowers? If so, what is the basic shape of the flower? What is each individual flower’s form and structure? Is it a multi-floret or a single flower? How many petals does it have? What is the flower’s colour range? Above are a few typical examples.

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Tree fruit

Tree fruit images © Ita McCobb

What colour, size and shape is the fruit? Is it multi-structured or a single fruit. Was it formed from a fertilized flower seed, cone or an end of stalk structure?

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Tree-family groups

Variety of tree families © Ita McCobb

There are an estimated 100,000 species of tree worldwide, which means that trees could make up an amazing 25% of all living plant species on this planet!

According to the Royal Botanic Gardens, Kew, London and the Missouri Botanical Garden, all plant families can be divided into four main groups – flowering plants (Angiosperms), conifers, cycads and allies (Gymnosperms), ferns and fern allies (Pteridophytes), and mosses and liverworts (Bryophytes).

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Flowering trees Angiosperms

Lime Tilia oliveri flowers © Ita McCobb

Flowering trees are flowering plants (Angiosperms) and are probably the species that first comes to mind when thinking of trees. Angiosperms are the largest and most species-rich group of plants – estimated to contain more than 250,000 species.

Typical of flowering trees are the Elm Ulmaceae, Walnut Juglandaceae, Beech Fagaceae (which group includes Oaks Quercus), the Birch Betulaceae, Horse-chestnut Hippocastanaceae, Maple Aceraceae, and Whitebeams, Service trees, Rowans Sorbus and Plums Prunus – this last group of four are all members of the rose family (Rosaceae).

The term “Angiosperm” comes from two Greek words – angeion meaning “vessel” and sperma, meaning “seed”. The Angiosperm family group is comprised of those plants that have flowers and produce seeds enclosed within a carpel. It includes herbaceous plants, shrubs, grasses and many, many trees.

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Conifers, cycads & allies Gymnosperms

Atlas cedar Cedrus atlantica © Ita McCobb

While all plant family groups (except Bryophytes) contain tree species, the majority of trees are Gymnosperms. Typical examples are the confusingly named Sago palm, Cycas revolute (a Cycadacea), which is not a true palm, the Ginko/Maidenhair (Ginkogoaceae), YewsTaxus baccata (family Taxaceae) and Conifers (Cupressaceae). There are around 1,000 species of Gymnosperm.

The largest group of Gymnosperms are the conifers (Cupressaceae – pines, cypresses and relatives) and the smallest is the ginkgo (Ginkogoaceae), which is a single plant species found originally in China but popular today in many cities and parks in temperate zones.

The word Gymnosperm comes from the Greek word gymnospermos meaning “naked seeds”. Not surprisingly then, Gymnosperms are also seed-bearing vascular plants but in which the ovules or seeds are not enclosed in an ovary. Gymnosperm seeds are produced on the exposed or uncovered surface of scales, on the leaf-like structures of cones or at the end of short stalks.

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Ferns & allies Pteridophytes

Common tree fern Dicksonia antarctica © Mmparedes

Tree ferns could be called the precursors of all modern trees since the first woody-stemmed plants to achieve any major height were ferns and, by the Middle Devonian period (around 400 million years ago) – one species called Wattieza had already achieved 8 metres in this period!

While any fern that grows with a trunk that elevates its leaf-like fronds above ground level could be called a “tree fern”, the plants formally known as tree ferns are Cyatheales, which group is made up of two families – the Dicksoniaceae and the Cyatheaceae.

Tree ferns are found in tropical and subtropical regions as well as temperate rainforests in the Southern hemisphere. The tree fern you’re most likely to come across in Europe is the Common tree fern Dicksonia antarctica.

As with all ferns, tree ferns reproduce by means of spores that form in receptacles called sporangia on the undersides of their fronds.

Unlike flowering plants, tree ferns do not form new woody tissue in their trunk as they grow. Instead, their trunk is supported by a fibrous mass of roots that expands as the tree grows.

Other than the Cyatheales, the only other fern that could be considered a tree fern (even though they have very short trunks of under 1 metre), is the Royal fern Osmundaceae.

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References: United Nations Environment Programme (UNEP), Division of Technology, Industry and Economics; Brian Capon, Botany for gardeners, Third edition, Timber Press; Royal Botanical Gardens, Kew, London; Missouri Botanical Garden; Latin for gardeners, Lorraine Harrison, Royal Horticultural Society; International Botanical Congress (IBC); RHS Gardeners’ encyclopaedia, Christopher Brickell ed., Dorling Kindersley; The Royal Horticultural Society; Frances Rose, The Wild Flower Key, Warne; Owen Johnson & David More, Collins tree guide, William Collins; Oxford English Dictionary, Oxford University Press.