Key to common UK street trees

From KeyToNature

Key to common UK street trees — Bob Press
Geographic Scope: Britain — Audience: General public and advanced school children — Collaboration: open — Status: Text completed, illustrations incomplete, Species page incomplete (species links in red are not yet created). — Edited by: Bob Press, G. Hagedorn (formatting and minor adaptations)

1		Leaves scale-like and often overlapping    ► 2 Scale-like leaves (Callitropsis nootkatensis) Scale-like leaves (Cupressus nootkatensis)
–		Leaves broader, not scale-like or overlapping    ► 3
2		Ultimate branchlets with white markings beneath, flattened and all spreading in one plane; fruiting cones 7-9 mm, each cone-scale with a small prickle in the centre    Lawson Cypress Chamaecyparis lawsoniana Female cones Habit of tree Habit of tree
–		Ultimate branchlets without white markings beneath, flattened but not all in one plane; fruiting cones 15-20 mm, each cone-scale with a prominent conical spine in the centre    Leyland Cypress Cupressocyparis × leylandii Branchlets and cone Habit of tree
3		Leaves opposite    ► 4 When leaves are borne in pairs, with one leaf on either side of the stem, they are opposite. The pairs all line up so the shoot has two rows of leaves. Sometimes the pairs alternate so that the shoot has four rows of leaves. They are said to be opposite and decussate. Even if there are no leaves of the tree, you can tell how they will be arranged by looking at the leaf buds. Twig with leaves opposite. The buds on this ash twig show the leaves will be opposite and decussate.
–		Leaves alternate    ► 13 When leaves are borne first on one side of the stem, then on the other, they are alternate. Spirally arranged leaves may also be referred to as alternate. ven if there are no leaves of the tree, you can tell how they will be arranged by looking at the leaf buds. Twig with alternate leaves.
4		Leaves simple, though often deeply lobed    Maples Acer species   ►► 5 A simple leaf is one where the blade forms a continuous surface i.e. it may be lobed or toothed, but is not divided into completely separate units. For a range of simple leaf types, see the glossary at the end of the key. Simple, entire leaf.
–		Leaves compound, divided into completely separate leaflets    ► 9 A compound leaf has the blade divided into three or more completely separate units. For a range of compound leaf types, see the glossary at the end of the key. This leaf has separate leaflets: it is compound. This leaf has lobes but not leaflets; it is simple.
5		Leaves green above, silvery white beneath    Silver Maple Acer saccharinum
–		Leaves of similar green on both sides    ► 6
6		Leaf lobes with numerous, small teeth; flowers in pendent clusters; fruits with wings more or less forming a right angle (at 90º to each other)    Sycamore Acer pseudoplatanus
–		Leaf lobes entire, or with few, large teeth; flowers in erect clusters; fruits with wings horizontal (at 180º to each other) or nearly so    ► 7
7		Leaves up to 8 cm long, lobed more than half-way to the base, the lobes with obtuse tips; flowers appearing with the leaves    Field Maple Acer campestre
–		Leaves > 8 cm long, lobed less than half-way to the base, the lobes with acuminate tips; flowers appearing before the leaves    ► 8
8		Leaf lobes toothed    Norway Maple Acer platanoides
–		Leaf lobes entire    Cappadocian Maple Acer cappadocicum
9		Leaves palmately divided, the leaflets radiating from a central point    ► 10
–		Leaves pinnately divided, the leaflets in two rows    ► 11
10		Flowers mostly white, with red and yellow blotches; fruits with numerous, sharp spines; winter buds very sticky    Horse-chestnut Aesculus hippocastanum
–		Flowers red or bright pink; fruits with few, if any, blunt spines; winter buds not sticky    Red Horse-chestnut Aesculus carnea
11		Fruits 1 per stalk    ► 12
–		Fruits paired on each stalk    Ash-leaved Maple Acer negundo
12		Leaves with 7-13 leaflets; flowers appearing after the leaves, purplish, without sepals or petals; fruits 2.5-5 cm long    Ash Fraxinus excelsior
–		Leaves with 5-9 leaflets; flowers appearing after the leaves, white, with 4 narrow petals; fruits 1-5-2.5 long    Manna Ash Fraxinus ornus
13		Leaves compound, with at least one pair of separate leaflets    ► 14 A compound leaf has the blade divided into three or more completely separate units. For a range of compound leaf types, see the glossary at the end of the key. This leaf has separate leaflets: it is compound. This leaf has lobes but not leaflets; it is simple.
–		Leaves simple, sometimes lobed but not divided into separate leaflets    ► 18 A simple leaf is one where the blade forms a continuous surface i.e. it may be lobed or toothed, but is not divided into completely separate units. For a range of simple leaf types, see the glossary at the end of the key. Simple, entire leaf.
14		Twigs spiny at base; flowers with 5 unequal petals, pea-like    False Acacia Robinia pseudoacacia
–		Twigs not spiny; flowers with 5, equal petals, not pea-like    ► 15
15		Leaves completely divided into 6 or more pairs of leaflets    ► 16
–		Lower part of leaf divided into 1-4 pairs of leaflets, upper part lobed but not completely divided    ► 17
16		Ripe fruits entirely orange-red to vermillion-red (occasionally yellow), with yellow pulp    Orange-/Vermillion-fruited Rowans Sorbus species
–		Ripe fruits white to pink or crimson, with white pulp    White-/Pink-/Crimson-fruited Rowans Sorbus species
17		Leaves with 1-2 pairs of leaflets, matt green above, grey-white woolly beneath; ripe fruit scarlet    Swedish Service-tree Sorbus hybrida
–		Leaves with 1-4 pairs of leaflets, glossy green above, thinly white hairy beneath; ripe fruit brownish-red    Thuringian Service-tree Sorbus thuringiaca
18		Leaves evergreen, often spiny    Evergreen Oak Quercus ilex
–		Leaves deciduous, never spiny    ► 19
19		Twigs spiny (spines sometimes very few)    ► 20
–		Twigs not spiny    ► 24
20		Leaves not lobed; spines on twigs 3-8 cm    ► 21
–		Leaves lobed to more than one-third of the way to the base; spines on twigs 1-2.5 cm    ► 23
21		Leaves with a rounded or bluntly pointed tip, completely hairless beneath; flower and fruit stalks hairless    Cockspur-thorn Crataegus crus-galli
–		Leaves with an acute tip, hairy at least on veins beneath; flower and fruit stalks hairy    ► 22
22		Leaves with whitish hairs scattered over the whole of the lower surface; flowers c. 2.5 cm across; ripe fruits orange-red    Hybrid Cockspur-thorn Crataegus x lavallei
–		Leaves with hairs on the veins of the lower surface only; flowers c. 1.5 cm across; ripe fruits red    Broad-leaved Cockspur-thorn Crataegus persimilis
23		Leaves usually with 5-7 lobes, the largest reaching more than two-thirds of the way to the midrib; flowers always white; styles and nutlets1    Hawthorn Crataegus monogyna
–		Leaves usually with 3 lobes, the largest reaching less than two-thirds of the way to the midrib; flowers white, red or pink; styles and nutlets 2-3    Midland Hawthorn Crataegus laevigata
24		Leaves lobed    ► 25
–		Leaves sometimes toothed but not lobed    ► 30
25		Leaves palmately lobed    London Plane Platanus x hispanica
–		Leaves pinnately lobed    ► 26
26		Leaves lobed to less than one-third of way to midrib; underside with a dense felt of hairs    ► 27
–		Leaves lobed at least one-third of way to midrib; underside sometimes hairy but not densely felted    Oaks Quercus species   ►► 28
27		Leaves whitish or silvery hairy beneath    Whitebeam Sorbus aria
–		Leaves greyish to yellowish hairy beneath    Swedish Whitebeam Sorbus intermedia
28		Leaves with 7-9 pairs of blunt-tipped lobes, rough above, hairy beneath; acorn cup with spreading or reflexed scales    Turkey Oak Quercus cerris
–		Leaves with 3-5 pairs of whisker-tipped lobes, smooth and hairless on both sides; acorn cup with short, close-pressed scales    ► 29
29		Leaves barely longer than wide, lobed c. half-way to midrib, shiny on both surfaces    Scarlet Oak Quercus coccinea
–		Leaves much longer than wide, lobed c. two-thirds of way to midrib, matt on both surfaces    Red Oak Quercus rubra
30		Bark creamy white or silvery white    ► 31
–		Bark grey or brown    ► 32
31		Bark silvery, developing black, diamond-shaped fissures with age; twigs and smaller branches weeping; leaf stalk smooth    Silver Birch Betula pendula
–		Bark creamy white, peeling in thin sheets; twigs and smaller branches erect or drooping at tips only; leaf stalk hairy    White Himalayan Birch Betula jacquemontii
32		Tree weeping; leaves > 10 times as long as wide    Weeping Willow Salix x sepulchralis
–		Tree not weeping; leaves < 10 x as long as wide    ► 33
33		Leaves with wavy, entire margins    Beech Fagus sylvatica
–		Leaves with flat, toothed margins    ► 34
34		Petals yellowish or absent; fruit dry    ► 35
–		Petals white, pink or red; fruit fleshy    ► 42
35		Fruits resembling small woody cones which persist on the tree all year    ► 36
–		Fruits not cone-like, falling from the tree in autumn    ► 37
36		Leaf margins toothed; cones in clusters of 1-3    Italian Alder Alnus cordata
–		Leaf margins doubly-toothed (the teeth themselves toothed); cones in clusters of 3-8    Common Alder Alnus glutinosa
37		Flowers and fruits in pendent catkins; petals absent; fruits each with a membranous wing    Hornbeam Carpinus betulus
–		Flowers and fruits in stalked clusters; petals present; entire fruit cluster attached to a single, membranous wing    Limes Tilia species   ►► 38
38		Leaves glabrous beneath except for tufts of hairs in the angles of veins; fruits not or only slightly ribbed    ► 39 The distribution of hairs on the leaf is an important character for identifying limes. Look closely (use a handlens) at the underside of the leaf. Are the hairs scattered across the entire surface or confined to the angles between the veins? Hairs confined to angles of veins.
–		Leaves evenly hairy beneath; fruits strongly ribbed    ► 40 The distribution of hairs on the leaf is an important character for identifying limes. Look closely (use a handlens) at the underside of the leaf. Are the hairs scattered across the entire surface or confined to the angles between the veins? Hairs scattered across the whole lower surface of the leaf.
39		Leaves with matt upper surface, the hairs in the vein angles beneath whitish; fruit rounded at both ends    Common Lime Tilia x europaea
–		Leaves with glossy upper surface; the hairs in the vein angles beneath reddish; fruit tapering at both ends    Caucasian Lime Tilia x euchlora
40		Leaves green on both surfaces    Large-leaved Lime Tilia platyphyllos
–		Leaves dark green above, silvery white beneath    ► 41
41		Branches weeping    Weeping Silver Lime Tilia 'Petiolaris'
–		Branches not weeping    Silver Lime Tilia tomentosa
42		Flowers with 3-5 styles; fruit with several seeds; bark without horizontal bands of pores    Crabs Malus species   ►► 43
–		Flowers with a single style; fruits with a single seed (stone); bark often with conspicuous horizontal bands of pores ( lenticels)    Cherries Prunus species   ►► 46
43		Leaves strongly tinged with purple; flowers dark or ruby red; fruit purplish red    Purple Crab Malus purpurea
–		Leaves green; flowers pink or white; fruits red or yellow    ► 44
44		Leaves hairy beneath; flowers pale pink fading to white, usually with 4 styles; fruits yellow    Japanese Crab Malus floribunda
–		Leaves hairless or hairy only on the veins beneath; flowers white, with 5 styles; fruits flushed with or entirely red    Siberian Crab Malus baccata
45		Flowers and fruits arranged in spreading or drooping spikes of 10 or more    Bird Cherry Prunus padus
–		Flowers and fruits solitary or in clusters of 10 or less    ► 46
46		Leaf margin with blunt and rounded teeth; flowers solitary, rarely in clusters of 2-3; fruit 2-3 cm    Cherry-plum Prunus cerasifera
–		Leaf margin with sharply pointed teeth; flowers in clusters of 2-6; fruit < 1.5 cm    ► 47
47		Leaf margin with teeth gradually narrowed into a long point tipped with a long, fine bristle    Japanese Cherry Prunus serrulata
–		Leaf margin with teeth rounded or narrowed into a point but not tipped with a long bristle    ► 48
48		Leaf stalk hairy; flowers generally pink, the stalk 1 cm    Spring Cherry Prunus subhirtella
–		Leaf stalk smooth; flowers white, the stalk 2-5 cm    Wild Cherry Prunus avium

The key is also available in a version for young school children.

Glossary (unfinished work)

acute Describes a leaf apex where the two edges forming the tip make an angle up to 90 degrees.

acuminate Describes a leaf apex which is long and tapered to a sharp tip.

alternate: Arrangement where the first leaf is borne on one side of the stem, the next leaf on the other side and so on.

catkin A cylindrical inflorescence of usually wind-pollinated flowers which lack sepals or petals.

compound Composed of several entirely separate parts. Compound leaves are made up of three or more leaflets. (See the gallery of images below.)

deciduous A tree which sheds its leaves all at once in autumn. It can also refer to parts of the plant which are shed early, e.g sepals.

entire Without any teeth, lobes or indentations.

evergreen A tree which retains its leaves all year round.

graft An artificial joining of one plant onto another.

foliage All the leaves and twigs together.

inflorescence All of the flowers and their arrangement.

infructescence All of the fruits and their arrangement.

leaflet A subdivision of a leaf.

lenticel Pore in bark allowing gases to pass in to and out of the trunk and branches.

native A tree occurring naturally in an area.

introduced A tree brought into an area by humans.

midrib Main vein running up the centre of a leaf blade.

obtuse Describes a leaf apex where the two edges forming the tip make an angle between 90 and 180 degrees.

opposite Arrangement of leaves in pairs, with one leaf on either side of the stem.

palmate With divisions radiating from a central point, like fingers spreading from the palm of a hand.

pinnate With divisions arranged in two parallel rows.

pollard A tree where the upper branches have been cut to encourage new growth.

simple Not divided into leaflets or lobes, opposite of compound. (See the gallery of images below.)

spike A long, narrow arrangement when referring to an inflorescence or infructescence. Spikes can be cylindrical, conical, branched or simple.

style Usually long and slender structure on top of the ovary and bearing the stigma.

Compound leaves

pinnate leaf

palmate leaf

Simple leaves

leaf with entire margin	leaf with toothed margin	leaf with doubly-toothed margin	leaf with spiny margin
pinnately lobed leaf	palmately lobed leaf