Turn back to the path and head left across the grass to the two spiky trees behind the floral display by a path junction. These also have very oddly-shaped leaves. They are (8) Ginkgo, a tree not known in the wild, but only from Chinese temple gardens. Long grown in the UK, it seems increasingly popular, not least in Cambridge streets (and hopefully not just because it happens to be highly pollution-tolerant!)

Across the path junction and to your right is a (9) Weeping Ash with long hanging branches but recognisable as an ash by the diagnostic black felted buds. Most weeping forms are the result of (deleterious) mutations in normally upright forms (branches are designed to be stiff to reach up for the available light!) All specimens of Weeping Ash (virtually every churchyard and cemetery seems to have one) are descended from a single tree found growing thus in Victorian times in Gamlingay Churchyard, about 15 miles south-west of Cambridge.

To its left is a (10) Caucasian Wingnut with long hanging streamers of yellow-green winged fruit. This is a very vigorous tree which is also being increasingly widely planted. Note that the leaves are pinnate (that is, with leaflets arranged along a central stalk) and the leaflets serrated, as with (Weeping) Ash. However ash leaves are arranged opposite one another on the shoot whereas those of wingnuts are alternate. The opposite/alternate distinction is the first feature you should check for when identifying a broadleaf tree. Opposite-leaved species are relatively less common and therefore easier to identify! [Note that even if the tree has no leaves you can still determine whether it is opposite or alternate by looking at the arrangement of buds or small branches, as these derive from, and hence mirror, the leaf arrangement.

To your right across the path is my favourite tree in Cambridge, a very fine mature specimen of a very uncommon tree, another wingnut, this time the (11) Chinese Wingnut. The leaves differ from those of the Caucasian Wingnut by the unusual leafy flanges running down either side of the leaf stalk. The wings on the fruit are also narrower (more like those of a mechanical wingnut!)

Behind the Chinese Wingnut and a little to the right is a mature specimen of a much more common but rarely noticed tree, the (12) Pillar Apple. This species is one of the few species which are naturally fastigiate, that is, strongly vertically-branching. Fastigiate trees tend to be of two types: those which branch repeatedly from a weak central leader and therefore stay narrow (for example the highly distinctive Lombardy Poplar used in the countryside as a windbreak), and those which branch repeatedly from a single point. The Pillar Apple is an example of the latter category, and as can be seen, the limited amount of space for branching means that the initially narrow tree soon develops middle-age spread as subsequent branches are forced ever further away from the vertical. Younger specimens are common as street trees and have distinctive 2-3cm yellowish-purple apples in autumn.

To the left of the Pillar Apple and behind the Chinese Wingnut is a tree with very large opposite leaves (or no leaves at all until mid-June; it is usually the last tree in leaf). This is the (13) Indian Bean Tree, long grown in the UK, but becoming more popular as a result of the warmer summers of recent years which the tree really needs to flourish. The tree has loose candles of white flowers in early summer and long black cylindrical seed pods which persist over winter. Nothing else has leaves so large, except the much less common woolly-leaved Foxglove Tree.

Just across the path from the Indian Bean is a small tree with alternate pinnate leaves with serrated leaflets. This is a (14) Black Walnut, easily distinguished from the Common Walnut which we will meet later, but a rather confusing tree unless walnuts are visible. The most distinctive feature is that the leaves typically lack a terminal leaflet (i.e. have even numbers of leaflets). This is still an uncommon tree. The nuts are edible but apparently the shell is extremely hard to break into.

Three more trees to look at briefly before we leave Christ's Pieces. The tree beyond the Black Walnut as you head towards the road is obviously a birch from the distinctive bark. However if you compare both the bark and the leaves with the those of the two birches behind you will see they are different species. The first tree is a (15) Paper-bark Birch , widely planted in parks, with bark that comes off in paper-like strips and larger leaves than those of the common native birches. Behind it are indeed two specimens of (16) Silver Birch. Birches tend to be difficult to identify reliably: Silver Birch is quite variable, usually with pendulous twigs, double-toothed leaves (i.e. each large tooth is itself toothed) and vertical black ‘diamonds’ at the base of the trunk, but some or all of these features may be missing, particularly in hybrids with the rather similar, and also native, Downy Birch.

Finally, as we exit Christ's Pieces at the corner, there are five small trees on the right, three with, at least early in the season, rather reddish leaves. They are all crabs of some kind (i.e. related to apples), and grown primarily for their spring blossom and/or autumn fruit. They mostly have unhelpfully similar and undistinguished small oval alternate leaves, and occur in a wide range of cultivated varieties and hybrids. The reddish ones in front are a cultivar of (17) Purple Crab, briefly spectacular when they flower in mid-spring; the others I have yet to conclusively identify!