Nature Menu

Introduction Beginner's Guide Where to find wild flowers Where to find butterflies Books and online tools Week by Week Nature Blog

Nature and Weather in South East England

This Week Message

For the latest observations, see the Nature Blog or the @SE_Nature Twitter feed.

The greening of the trees

Other April pages: Intro and woodland flowersVerge and field flowersBlossom and shrubsBirds Butterflies, insects and farm animalsWeather

Put your cursor over any photo to see its caption, or click here to see more April tree photos

Without doubt one of the most dramatic changes in the countryside in April is the return of foliage on bushes and trees. They go from a drab brown at the start of the month to glorious fresh greenery at its end. En route, various trees get briefly highlighted in the treescape, and woods acquire a lurid bright green look that is quite overpowering on sunny days.

As a rule the leafing moves from shrubs to smaller trees and on to larger trees, but there are exceptions – for example, weeping willows and horse chestnuts, which leaf very early. These apart, the sequence is greening of the lower, shrubby part of the woodland (the understory) in the first week, a fuzz on smaller trees in the second week, then an explosion of greenery on most remaining trees in the third week (as early as the second week in the hot April of 2011, though not till the fourth week in 2013 and 2015, and not until the first week of May after the cold April of 2012). Within an individual species smaller younger plants or saplings also often put out leaves earlier than mature trees - presumably programmed to do so by evolution in order to catch the light reaching the woodland floor before the tree canopy closes.

The very first leaves come way back in winter. As well as evergreens such as holly and yew, some deciduous plants never entirely lose their foliage or start putting out new growth as early as December or January - privet, buddleia and honeysuckle fall into this category. Bramble for the most part also keeps a few leaves over the winter and in late March puts out new leaf shoots from the middle of its stems. All of these can still be quite tentative in the first half of April - that is the new leaf shoots are quite small - but they fill out in the second half. Bramble in particular, being so ubiquitous, contributes a lot to the greening of hedgerows and the understory.

Other little noticed contributors to the greening of hedgerows and woodland understory include cherry plum, which leafs once its blossom is over, typically some time in late March (see March trees and shrubs), and elder, whose leaves have also been growing slowly since as early as January and rapidly grow to full size in early April. Snowberry may have started to put out leaves out at the end of March and these achieve full size by mid April. Wild rose may also have started at the end of March, but its foliage does not really become big until the second half of April. Dogwood leaves can remain small all month, but stand out attractively against its maroon branches. In hedgerows the climbing plant travellers joy also leafs up in the first half of the month.

Much more obvious is the leafing of hawthorn, which has a huge impact on the appearance of the countryside, covering large swathes of hedgerow and understory with a lovely green fuzz. Some smaller ones may have already leafed in the second half of March, and in 2007, 2012 and 2014 all hawthorns leafed at this time, while in 2011 it was in the fourth week of March. But more usually this happens in the early part of April - the first week in 2008, 2009 and 2010, the second week in 2016, the end of the second week in 2006, 2013 and 2015. The leaves can remain small until mid month, however.

On blackthorn the falling blossom in the third or fourth week gives way to new foliage. Some smaller blackthorns go straight to leaf without flowering at all, however, or have lower twigs leafing while the upper ones are still in flower.

Moving up in size, hazel tends to have small new leaves at the start of April, having started in late March (though in 2016 some trees had not yet entirely dropped their catkins by this point). These leaves remain very small till late in the month, however. At this early stage they look almost identical to those of hornbeam, to which they are related, but the hazel ones have the buds of the nut cases to come nestled in the middle of them.

Hornbeam leaves are often, though not always, preceded by a mass of catkins. Typically this happens in early April (in the second half of March in 2014, the last ten days of March in 2016, but not till the second half of April in 2013). The general sequence is that the catkins (the male flowers) come out first, and then tiny leaves and the almost invisible female flowers (which droop at the end of the twig), and then the catkins all fall, carpeting the woodland floor. But very occasionally the leaves appear first and then the catkins, and some trees produce only leaves and female flowers (though all trees are in theory bisexual). In some years catkins seem less common than in others. Whatever, one is suddenly aware of just how many hornbeams there are in some parts of the south east, for example the Weald. (They are not common elsewhere in the country.) Later in April the female catkins morph into the beginnings of the tree's characteristic seed clusters.

The hornbeam is not the first large tree to leaf, however. That honour goes to the weeping willow, which can put out new leaves and catkins as early as the first week in March, and which shines a bright yellowy green in the landscape as a result.

In early April horse chestnuts follow, their brown sticky buds expanding into monstrous ovals that look like some weird fruit, and then overnight producing limp bright green leaves. This can happen as early as the first week, though it was a week to ten days later in 2006, 2008, 2009, 2013, 2015 and (in places) 2016. If you wonder why you then almost immediately find green leaves on the ground, it is because squirrels eat the flower buds and discard the leaves. At the very end of April (mid April in 2011 but not till mid May in 2013 and 2016) they start to put up their spikes of candle-like flowers.

Also at the start of April (not till the second week in 2016, and the last ten days of the month in 2013) Norway maple seems to be bursting into bright yellow-green leaves, but on closer inspection is seen to be producing flowers, with some leaflets. It remains a striking sight for a couple of weeks. Once the flowers fall they give way to leaves.

Larch can also be briefly quite noticeable in early April. The only coniferous tree to lose its needles in winter, it has already started to put out soft tassels of new greenery in late March (not till the third week of April in 2013) as well as maroon cone-like flowers. These are the female flowers, which will soon morph into cones: the male ones (seen on the same tree) are yellowish and small, looking like undeveloped buds.

Also at the start of April pussy willows (a collective name taking in goat willow or sallow and grey willow) are at the height of their catkin phase. There are two types of tree – male, which lose their catkins and leaf mid month, and female, which retain green catkins to the end of April, leafing later in the month. (In 2007, 2011 and 2012 the male catkins had all but finished by the end of March due to hot weather in that month. In 2013 pussy willows started to bud in early March but were put in suspension by the cold weather: catkins finally came out in the second week of April and lasted till the fourth week. In 2016 male catkins faded by mid month but leafing did not start till late in the month).

Another willow - osier, which grows by rivers - has similar male catkins to pussy willows, though densely packed on the branches. Much more common in the south east is crack willow, which often hybridises with white willow. They put out leaves and catkins together as early as the start of the month (the third week in 2013), the male catkins long and yellow and sometimes looking like curly caterpillars, the female green. The male ones fall to the ground later in the month but the female ones remain on the tree.

Also in mid April (in the fourth week in 2013) the short brown catkins that have hung on birch trees all winter lengthen out (causing big problems to hayfever sufferers: birch pollen is very allergenic), sometimes appearing before the leaves and sometimes with them. The catkins can last into the early part of May.

By this time attention has switched to the larger trees. A few sycamore may have started leafing in late March, but at the start of April most are still at budburst stage (when the bud casing parts to show green leaf colour). It can take a while for them to go from this to leafing proper, and some trees seem to be faster about it than others (especially young ones). But by the second week or so (third week in 2012 and 2016, fourth week in 2013 and 2015) its huge leaves are appearing, accompanied by grape-like tassels of flowers. Some sycamore leaves look brown and tired when they unfold.

Field maple also produces leaves and and flowers simultaneously from as early as the second week, as do more ornamental park maples. Sugar maple, a popular street tree, has red flowers in late March and early April. Also mid month (though not till the end of the month in 2013 and 2016) mid-sized trees like alder, lime, poplar and rowan are putting out leaves (the latter easy to mistake for ash due to its similar leaves).

On alders and limes these leaves can remain very small till well into May, (though not in hot April 2011, when they rapidly grew to full size). Poplars should have produced their fat red (more orangey on some species) catkins in the second half of March: if not (as in 2015 and 2016), they do this early in April. Once the catkins fall, the tree puts out leaves - brown ones in some poplar species, which then slowly turn green.

London plane also comes into leaf mid month, somewhat tentatively at first, and put out new globular flowers - green male ones and pink female ones. It may also shed its old seed balls, producing piles of silky tassels on the ground, though sometimes this is delayed till May. Wych elm has clusters of flat seeds and leafs from mid month (from the start of the month in 2011): the surprise here is to see an elm growing at all, since most were decimated by Dutch Elm Disease in the 1970s. Note also the strange pale leaves of whitebeam, which unfold from an upright centre like tulip petals towards the end of the month.

Perhaps the most striking tree when it comes out is the beech, however. From the third week (last week in 2010 and not till early May in 2012, 2013 and 2016) its lurid new leaves hang in limp lines, like washing hanging out to dry. The appearance of beech leaves often coincides with the fullest phase of the bluebell season (though this was not true in 2012 and 2016), and its leaves remain an entrancing bright green long enough to contrast strikingly with any bluebells underneath them at the end of the month or in early May.

Also by the third week oak is in leaf, producing both foliage and yellow-green tassel flowers simultaneously. The leaves are slow to grow and so the flowers often dominate to begin with, but they are little noticed because from a distance they look like new foliage. (In 2013 oaks did not come out till the end of the month, while in 2016 - otherwise a somewhat late year for leafing - oaks were out widely from the second week. They remained a bright yellowy-green feature in the landscape for the whole rest of the month, and a few were still starting to leaf right at its end.)

That leaves ash as the main tree that is still largely bare. It puts out its strange flowers - looking like frizzy lettuce - as early as the start of the month, though this is very variable. In some years there are a lot of them (for example 2013, when it did not flower till the fourth week) and some years (such as 2014) there are none at all. There are in fact two types of flower - the more compact male ones and the female ones which are already flecked with the seeds to come. As the month goes on the male flowers fall to the ground while the female ones lengthen into feathery fans and slowly become more seed-like. Either way the tree does not leaf until the very end of the month, and even then its foliage can remain tentative right into the first part of May. (In 2016 most did not leaf till the second week of May, flowering having started mid April.)

One other laggard is sweet chestnut, which does not leaf till May, though it may just be showing a bit of budburst by the end of April.

More April pages:

© Peter Conway 2006-2016 • All Rights Reserved

No comments:

Post a Comment