This is an edited version of an article from the Friends of Battersea Park Review.
On 29 June we welcomed Greg Packman to the Park for a second time, this time for a guided tree walk on Summer Tree Identification. Greg, who works as an arboricultural officer with the Royal Parks but is keen to share his knowledge about trees with others, began by telling us that sources of help in identifying trees include books (for example the Collins Tree Guide), smartphone apps, and dichotomous keys. Keys use pairs of characteristics to guide us through a decision tree towards a final identification of the species.
Over the next two hours Greg explained the various features of a tree which help us to distinguish one species from another species – see the table below. He focussed on the features which were most apparent on the trees in June, but he also mentioned features which can be seen at other times of the year, including features which he points out on his Winter Tree Identification walks. Particular species of tree have other identifying features which are not included in the table below. In Battersea Park there are examples of all the trees mentioned in this table.
Greg stressed the importance of not only looking at obvious features such as leaves, flowers and bark, but also looking at the ground beneath the tree, using our sense of touch to feel the bark and both sides of a leaf, and our sense of smell to detect the smell of a flower or a leaf crushed between thumb and fingers (but don’t do this with poisonous species such as Yew).
(b| Part of the tree | Feature | Examples |
|---|---|---|
| Leaves | Are the leaves opposite or alternate? | Opposite leaves are less common, and include Ash, Maple, Sycamore, Horse-chestnut, Catalpa, Dogwood. Alternate leaves include London Plane. |
| Are the leaves simple or compound? | Compound leaves include Ash, Horse-chestnut, Walnut, Tree of Heaven, Rowan, Elder, Gleditsia, Rose. | |
| What shape is the leaf? | Limes have heart-shaped leaves. Cherry Laurel has long leaves. Some species of Elm have asymmetric leaf bases. Horse-chestnut have palmate compound leaves (lobes radiate from a central point). Ash have pinnate compound leaves (leaflets arranged along the midrib). The shape of the leaves of English Oak and Turkey Oak, and Norway Maple and Field Maple are different. | |
| Does the leaf have lobes? | English Oak, London Plane, Maple | |
| Does the edge of the leaf have teeth? | Hornbeam, Hazel, Sweet Chestnut, Lime, Elm. | |
| Does the surface of the leaf feel rough or smooth? | English Oak is smooth on top. Turkey Oak are rough on top and minutely felted below. Wych Elm are rough on top. | |
| Is the surface of the leaf hairy or hairless? | Holm Oak are usually smooth on top and felted below. | |
| Is the back of the leaf different from the front in any way? | See above. Silver Lime, Silver Maple and Holm Oak are lighter underneath. | |
| What is the size of the leaf? | Sycamore leaves are usually larger than the leaves of Field Maple. Catalpa have large leaves. | |
| Do the leaves smell when crushed? If so, what do they smell like? | Cedar has a strong smell which insects find unpleasant. Sweet Gum smells of gum. (Don't crush the leaves of posionous trees such as Yew.) | |
| Is there a leaf bract (a kind of modified leaf) on the flower/seed stalks? | Lime | |
| Are the leaves spiny? | Holly | |
| Deciduous or evergreen | Do the leaves fall in winter? | Pines and Holm Oak are evergreen. |
| Leaf stalks | How long are the leaf stalks? | English Oak has short stalks. Sessile Oak, Sycamore, Catalpa and Cherry have longish stalks. |
| Flowers | What do the flowers look like? What colour are they? | Red Horse-Chestnut has red flowers. |
| Do the flowers go up or down? | Norway Maple and Small-leaved Lime go up. Sycamore and Common Lime go down. | |
| Buds | What shape are the buds? | Lime has plump, fairly round buds. Hazel has plump oval buds. Beech has pointed buds. Turkey Oak buds have protruding whiskers. |
| How far apart are the buds? | Wild Cherry has clusters of buds on flowering spurs. English Oak and Turkey Oak have clusters of buds at shoot-tips. | |
| Is there a terminal bud? | Oaks have a terminal bud (fig. 4). | |
| What colour are the buds? | Common Ash has black buds, whereas Narrow-leaved Ash has brown buds. | |
| What does the bud feel like? | Horse Chestnut has sticky buds. | |
| Are the buds opposite or alternate? | If the buds are opposite, the leaves will also be opposite. | |
| Shoots | Are the shoots smooth or warty? | Silver Birch often has warty shoots. |
| Can you see leaf scars where last year’s leaf was attached? | Horse-chestnut has a semi-circular mark. Walnut has a mark like a monkey-face. | |
| Branches | Are the branches opposite or varied? | If there any many opposite branches, the leaves will also be opposite. |
| Thorns | Does the tree have thorns? | Hawthorn |
| Seeds and fruit | What do the seeds or fruit look like? | Oak has acorns. Maple and Wingnut have winged samaras. Ash has long drooping clusters of winged seeds. Elm has pale round samaras up to 1” diameter with a brown or pink seed in or near the middle. |
| What shape are the seeds? | Field Maple has horse-shoe shaped seed pairs. | |
| Do the seeds have stalks? | Acorns on English Oaks have stalks, but acorns on Sessile Oaks do not. | |
| Catkins | Does the tree have catkins? | Birch, Poplar, Willow, Alder and Hazel have catkins. |
| Bark | Is the bark ridged, smooth, flaky or paper? | Oak has ridged bark. Beech has fairly smooth bark. London Plane has flaky bark. Silver Birch has papery bark. |
| What colour is the bark? | Siver Birch has white or light grey bark. Red-barked Birch has red bark. Cherries have bark of different colours. | |
| Habit | What is the overall shape of the tree? | Lombardy Poplar is columnar. |
| Suckers | Does the tree have suckers? | Poplar, Robinia and Caucasian Wingnut often have suckers. Common Lime often has suckers, whereas Broad-leaved Lime rarely has suckers (unless grafted onto Common Lime). |
| Ground | Are there are clues on the ground below the tree, such as fallen leaves, seeds and twigs? | Species of Pine have different numbers of needles grouped together. |
The answers to these questions narrow the range of possibilities. For example, if you see that the leaves are opposite, that eliminates over half the species of tree which the tree could be. However some species (including some Hawthorns and some Cherries) can only be identified at a particular time of the year, for example when they are in flower.
Greg pointed out many of the features mentioned in the table as we walked round, and as always he was able to add interesting information about the trees.
Details of Greg’s forthcoming tree walks in the Royal Parks and elsewhere are given on his website at https://www.gregtalkstrees.com/tree-walks.