Glossary of Botanical Terms used in Tree Identification
Achene a small, dry, single-seeded fruit that does not split open. The fruit of the London Plane is a dense ball of achenes
Alternate Leaves may arise from the shoot in opposite pairs or may alternate along the shoot. The way they are arranged may help to identify the tree. Most trees have alternate leaves. Examples are Oaks, Beech, Hornbeam, Alders, Willows and Poplars. Lateral buds of these trees will also be alternate.
Angiosperms 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.
Anther The male part of a flower is made up of an anther supported on a stalk called a filament. When ripe, the anthers split open to release pollen grains. Each grain contains a single set of male chromosomes.
Asymmetric Many trees have leaves that are perfectly symmetrical about the central rib but some trees have leaves that are asymmetric with the two sides being unequal in shape or size. Elms can be identified by their leave’s characteristic asymmetric shape.
Axil When a lateral bud develops into a leaf, a new bud is formed in the axil between the new leaf and the shoot. This bud is called an axillary bud.
Bark The outermost layers of the main stem of a tree. Bark consists of an inner layer of phloem and an outer layer of dead cork. The function of the cork layer is to keep out water and diseases and, in some cases, protect the tree from fire. The function of phloem is to carry sugars and nutrients from the leaves or storage vessels to the rest of the tree.
Berry A fruit produced from a single ovary in which the seeds are immersed in a fleshy layer and then an outer skin. Examples are grapes, tomatoes and elderberries
Bole The main stem of a tree below the branches.
Bract A specialised leaf that grows under a new flower when it is first formed and supports and enfolds it. Usually bracts do not grow as the flower develops but in some plants they become enlarged and distinctive as in Limes and the Handkerchief Tree.
Broadleaf trees Generally they have wide leaves with veins and 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.
Bud In Britain most tree growth occurs in spring and summer. During the growing season the tree produces buds ready for next years growth. These buds remain dormant during the winter and open in the following spring. Inside each bud are tiny preformed leaves, shoots or flowers.
Capsule A dry fruit formed from several fused ovaries that, when mature, splits open to release seeds. Examples are Poplars and Willows, which release many seeds. Another is the Horse Chestnut, which has a fruit that splits open to release only one seed (a conker)
Carpel The female part of a flower that includes the stigma, style and ovary.
Catkin A cluster of unisexual flowers that have no petals. On wind pollinated trees catkins are long and thin and usually hang down below the shoot. These are found on Oak, Poplar, Birch, Alder, Hazel and Hornbeam.
Clone Plant breeders create clones by taking cuttings (shoots cut from the parent plant) and planting them, for example, in moist ground. So a clone is genetically identical to its single parent.
Cluster A term used to describe a number of needles or buds that arise at a single point.
Compound A simple leaf is made up of one piece. It is undivided. A compound leaf is divided into several leaflets.
Cone Conifers, unlike Broadleaf trees, do not have flowers or fruit. They have male and female cones. The botanical name for a cone is a strobilus.
Cone Scales The female cones of Pines, Spruces, Firs, Cedars and Larches have a series of overlapping woody scales arranged spirally along the central stem. These form the outer protective coating of the cone and are known as Cone Scales.
Conifer trees Have leaves that are needle-like or scale-like. They bear cones not 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 rest have been introduced.
Coppice A tree that has been cut back at regular intervals to near ground level. The cut wood is then used for fuel or as poles for building. The tree then grows again from the stump. Coppicing is an ancient woodland practice often carried out on Hazel.
Cultivar A Cultivated Variety (usually shortened to Cultivar or cv.) is a plant variety that has been produced in cultivation as opposed to one that arose in the wild. A plant variety arises when plants grown from seeds are slightly different from the parent plant. This could be a difference in flower colour or leaf shape. Plant breeders then take a cutting from one of the plants and grow a new plant that is then a Cultivar.
Deciduous trees Shed their leaves in autumn and grow a new set in spring. Most Broadleaf trees are deciduous but some, such as Holm Oak and Holly are Evergreens.
Dioecious The Greek word for “2 households”. Refers to trees that have male flowers on one tree and female flowers on another tree. Examples are Poplars and Willows.
Drupe A fruit that has its seed enclosed by a stony layer and then a fleshy layer and an outer skin. Wild Cherry, Bird Cherry, Plum, Blackthorn and Walnut fruits are drupes. A cherry stone is a good example of a seed enclosed by a hardened ovary wall. Mulberry fruits are made up of a number of drupes fused together.
Evergreen trees keep their leaves all year. Most Conifers are evergreen but some conifers, such as the Larch, Swamp Cypress and Dawn Redwood are deciduous.
Fastigiate A botanical term used to describe a tree in which the branches grow almost vertically upwards. One example is the Lombardy Poplar.
Filament In a flower the male part – the Stamen – is made up of an anther supported on a stalk called a filament.
Flower The reproductive unit of a Flowering Plant such as a Broadleaf tree.
Follicle A type of fruit like a legume, which on ripening, splits down one side only to release the seeds. The legume splits down both sides. The Magnolia fruit is an aggregate of many follicles.
Fruit The structure that develops from the ovary and its base and includes the seeds.
Gymnosperm Conifers belong to a group of plants called Gymnosperms. This word comes from the Greek word for ‘naked seeds’. The seed is referred to as ‘naked’ because it does not sit within an ovary – as found on Broadleaf trees. In Conifers the woody cone scales are packed closely together and the seed is protected between them.
Hybrid A plant resulting from a cross between 2 genetically different parents.
Inflorescence A flower bud may produce a solitary flower or may develop into a cluster of flowers, called an inflorescence by botanists. The structure of the inflorescence may be complex but can be used to identify the tree. The Elder has a flat inflorescence whilst the Horse Chestnut has a vertical column.
Key Called a Samara by botanists it is a dry, winged, single-seeded fruit that does not split open. Common Ash trees carry bunches of Keys. The wings help to carry the seed away from the parent tree.
Lateral Refers to buds (or leaves) produced at particular points on the shoot called nodes. If there is one bud at each node, the buds are said to be alternate. If there are 2 buds at each node they are said to be opposite.
Leaf The main photosynthetic organ of a tree. This is a process in which carbon dioxide from the air is combined with water in the presence of light to produce sugars and oxygen.
Leaflet A compound leaf is divided into several leaflets arranged in 2 rows either side of a midrib like a feather.
Legume A fruit that is made up of a 2-part pod that splits open, down both sides, to release seeds. An example is the False Acacia.
Lenticel The horizontal lines on Silver Birch bark are lenticels. These are pores through which gases may pass. Lenticular means lens-shaped.
Lobe A rounded or pointed segment of a leaf that is separated from other segments by a gap that does not reach the midrib of the leaf. Oaks, Hawthorns and Maples are examples of leaves that are lobed.
Monoecious The Greek word for “One Household”. Some Broadleaf trees have male and female flower parts that are separated but on the same tree. These trees are known as monoecious. The Silver Birch is an example.
Needle The leaves of Pines, “true” Cedars, Larches, Spruces, Firs and the Common Juniper are long and thin and needle-like and in many guides, including this one, they are simply called needles.
Nut A dry, single-seeded fruit with a woody coat that does not split. Examples are Hazel, Oak, Beech and Sweet Chestnut. The nut sits in a cup, which either partly encloses it (oak and Hazel) or fully encloses it (Beech and Sweet Chestnut).
Opposite Leaves may arise from the shoot in opposite pairs or may alternate along the shoot. The way they are arranged may help to identify the tree. Many trees have opposite leaves. Examples are Elder, Maples, Ash and Horse Chestnut. Lateral buds of these trees will also be opposite.
Ovary The part of the carpel that contains the ovules. An ovule is a plant structure that contains a female egg and other tissues that will develop into a seed after fertilisation. The ovary and other floral parts develop round the seed to form the fruit.
Palmate leaf Has up to 5 leaflets radiating out from a single point. Horse Chestnuts have palmate leaves.
Panicle A flower cluster or inflorescence is called a panicle if the main stalk grows continuously but branches (with flowers) are added, rather than single flowers. In the Horse Chestnut panicle, the oldest flowers are at the base and the newer flowers are at the top. This panicle grows upright but on some trees the panicle (e.g. the Sycamore) hangs down, in which case it may be called a tail.
Perfect Flower Some trees have male and female parts combined in one flower. These are called perfect flowers or bisexual flowers.
Petals Attract and then guide pollinators such as insects to the centre of the flower where there is a source of nectar in the nectary.
Phloem Bark consists of an inner layer of Phloem and an outer layer of dead cork. The function of Phloem is to carry sugars and nutrients from the leaves or storage vessels to the rest of the tree.
Pinnate A term used to describe a compound leaf that has leaflets arranged in 2 rows either side of a midrib like a feather. Many trees, such as the Common Ash and Common Rowan, have pinnate leaves.
Pod A dry fruit that splits open to release seeds. Found in members of the pea family such as the False Acacia, Laburnum and Judas Tree.
Pollard A tree that has been cut every few years, 2 to 4 m above the ground. The cut branches were used for feeding livestock or for fuel. After pollarding, the tree re-grows to produce another crop. Pollarding has the advantage that the new growth is out of reach of grazing animals. The practice of pollarding was carried out on Hornbeam, Beech, Oak and Elm and is still carried out on Willows.
Pollination Pollen grains contain male DNA. The grains are either dispersed by the wind or picked up by insects and transported to the female parts of another flower. In Broadleaf trees the pollen grain lands on the stigma, which is normally at the tip of the style. This process is called pollination. In Conifers a wind-blown pollen grains drifts into the cone and sticks to a drop of sugary fluid, called a pollination drop. As the fluid evaporates, the pollen is drawn into the cone to contact the ovule, which contains the female sex cell.
Pome A fleshy fruit in which the seeds are surrounded by a core, then a firm fleshy layer and then a skin. The core and seeds are produced from the ovary. The firm fleshy layer and skin are produced when the base of the flower grows round the core. Examples are Crab Apple, Pear, Hawthorn, Wild Service, Rowan and Whitebeam.
Raceme A flower cluster or inflorescence is known as a raceme if individual flowers on short stalks are continuously added to a central stalk as it grows. Examples are Bird Cherry, Portugal Laurel and False Acacia. In a raceme the oldest flowers are near the base and the newest flowers are near the tip of the growing shoot.
Samara A dry, winged, single-seeded fruit that does not split open. Examples are found on the Maples, Ash and Tree of Heaven. A Samara is sometimes called a key. The wings help to carry the seed away from the parent tree.
Scale-Leaf Conifer leaves may be shaped like a scale on a fish or reptile. Cypresses have overlapping scale-like leaves that cover the shoot and are known as scale-leaves.
Sepal The outermost layer of petals that in most plants is green, as in the Wild Cherry flower. In the case of the Magnolia flower, the petal and sepal cannot be differentiated and so are called tepals.
Sessile When a leaf or an acorn sits right on the shoot and has no stalk it is known as sessile. An example is the Sessile Oak acorn.
Shoot The words twig and shoot are both used for small, thin branches of woody plants.
Shrub Has several stems arising from below ground level instead of the single stem of a tree. It usually does not reach a great height. In practice many plants can grow like trees or shrubs. The Hazel and Elder are examples.
Simple A simple leaf is made up of one piece. It is undivided. A compound leaf is divided into several leaflets.
Stamen The male part of a flower, the stamen, is made up of an anther, which is supported on a stalk called a filament.
Stigma A receptive area of the female part of a flower, usually located at the tip of the style on which pollen grains land in the process of pollination.
Stomata On some Conifer needles there are lines of white dots. These are called stomata. They are pores, which allow gases to pass in and out of the leaves. The pattern of dots can be used to identify the tree
Strobilus Conifers have male and female cones. The botanical name for a cone is a strobilus.
Style In the female part of a flower the style links the stigma to the ovary. After a pollen grain lands on the stigma a pollen tube grows from the stigma down the inside of the style to the ovary.
Teeth The edge of a leaf or leaflet may be smooth or it may have teeth. The Hornbeam leaf for example has large teeth and, between them, several small teeth. This is known as double-toothed. The arrangement of the teeth may be used to identify the tree.
Tepal The sepal is the outermost layer of petals and in most plants is green as in the Wild Cherry flower. In the case of the Magnolia flower the petal and sepal cannot be differentiated and so are called tepals.
Terminal Buds are formed at the end of the shoot. Lateral buds are formed at the junction of the leaf and shoot.
True Cedars Members of the genus Cedrus – Atlas Cedar, Cedar of Lebanon and Deodar are called “true cedars”. There are three “false cedars” in this guide – Incense Cedar, Western Red Cedar and Japanese Red Cedar. They are called Cedars because they have wood that smells and looks like the wood of the “true cedars”.
Variety In any wild plant population that occurs over a wide geographical range, differences may evolve in the form of the plant. When the form is distinct from the originally described plant, the new form is called a variety, abbreviated to var. The Black Pine pinus nigra has several varieties, which grow in different parts of Europe.
Xylem A Greek word for wood. There are two woody layers. The inner layer is called heartwood and consists of dead xylem cells. The outer woody layer is called sapwood and consists of living xylem cells, which transport water from the roots to the leaves.