Ireland's Biodiversity Awareness Campaign

Autumn - Trees and Plants

Autumn provokes remarkable and striking changes in Ireland’s deciduous plants and trees. Green hues of summer foliage are transformed into vivid colours of yellow, red, orange, crimson, and brown, before leaves finally drift off trees.

Why do leaves fall?

The leaves on evergreen trees such as pines, firs and spruces are able to survive the winter as their needle shape and waxy coating makes them more resistant to dry conditions and freezing temperatures. Deciduous leaves however are vulnerable to damage as they are thin and not protected by any thick coverage. During the winter, when there is less free water available in the soil, it is difficult for the leaves to stay turgid and leaf tissue would be damaged. Deciduous plants therefore enter a dormant period, shedding their leaves to adapt to the harsh conditions.

How do leaves start to fall?

Changes in day length, falling temperatures and lower sunlight intensity triggers a decline in plant growth regulators and leaf tissue starts to die. When a band of dead cells has formed at the base of the leaf stalk, the leaf detaches from the twig and aided by the wind is carried off. 

Why do leaves change colour before falling?

Chlorophyll, the pigment that dyes leaves green is abundant in the growing season,  masking all other leaf pigments. However, when shorter, colder autumn days, induce the process of leaf-breakdown, chlorophyll is one of the first compounds to breakdown and other pigments such as those that cause red and bronze hues begin to show. These autumn toned pigments accumulate in leaves and build up as the leaf ages.

Autumn fruits & nuts

After flowers are fertilised, the female reproductive organs often develop into fruits or nuts. In Autumn, these appear in abundance on many trees and shrubs across the country. In a ‘mast year’, vegetation produces a significant abundance of fruit. The term originally applied solely to trees, like oak trees, that produced fruit useful for feeding farm animals. The term "mast" comes from the Old English word "maest", meaning the nuts of forest trees that have accumulated on the ground, especially those used as food for fattening swine.

As well as looking beautiful, berries, fruits, nuts and cones contain the seeds of a plant and are therefore crucial for the cycle of life. They also provide an important food source for animals and birds over the winter months. Birds play an important role in seed dispersal - it is interesting to note that some seeds can not germinate unless they have been through a digestive tract. The seed is worn down in the birds digestive tract and then deposited in the animals faeces. The nutrients in the faeces can help the seed to grow.

Look out for the following over the autumn season:

Horse Chestnut ‘Conkers’
The flowers of the Horse Chestnut tree give rise to a spiky, fleshy, green fruit. These fruit split open in September to reveal 1-3 large, shiny, mahogany-coloured nuts commonly known as ‘conkers’. Conkers are the tree’s seeds. This species of Chestnut is not edible for humans but is often eaten by cattle and deer, or used in children’s games.
Sycamore  ‘helicopters’
In Spring, small pale green flowers hang in clusters from Sycamore twigs. The female of these flowers develop into winged seeds known as ‘helicopters’ which, when ripe in the autumn, spin away from the parent tree in the wind. This form of seed dispersal makes the Sycamore a good coloniser.
Beech nuts
Female Beech tree flowers develop into spiky, woody husks which each contain a pair of triangular, shiny brown nuts
Ash trees have bunches of winged seeds, which are called ‘keys’ after they way they hang down from the ash twigs. These stay on trees for a while after the leaves have fallen.
Scots pine
Seeds ripen in cones in Sept and October and are dispersed between December and March. Our red squirrel is a big fan of the seeds of this tree more than any others, so keep an eye out in a Scots Pine near you!
Hazel Nuts
Hazel trees can be found throughout the countryside. The hazel tree is not only a source of food, found in the nut of the tree, but the timber is also strong and flexible. The Burren in Co. Clare is home to Hazel scrub as are the Glens of Antrim. In Autumn the seeds of the tree are found – hazel nuts. It is best to collect the nuts directly from the tree when they beginning to turn brown.
Get Picking !!
In Ireland, apples ripen anytime between the end of August and October. If an apple on a tree comes off with a gentle twist this is a sign that it is ripe and ready for picking.
Crab Apple
Crab apples normally ripen in October. They are ancestors of domestic apples and are often grown in farmsteads but can also be found in hedgerows. They can be easily collected in large quantities in autumn by shaking them down from the bush when ripe. This fruit is great for making apple jelly and also used as pectin for jam making.
Blackberries are the fruits occurring on brambles. They are an important food source for insects including wasps and butterflies, birds, mammals, and even us! They are a popular fruit to be eaten fresh, made into jam or used in baking.
Rose hips
Rose Hips are high in vitamin C (higher than blackcurrants or oranges) and were commonly collected by children during WW2 to make rose hip syrup. They contain small seeds which must be removed before being eaten.
Elder berries
The Elder Tree is mostly found in shaded areas and in or near hedgerows. The berries of this tree can be seen in hanging in clusters of dark red/black berries. These berries are great for making wine and jam. The Elder tree also harbours a huge variety of wildlife, the berries provide food for birds, and the hollow branches provide nesting chambers and shelter for insects.
The purple fruits of the Blackthorn tree are called sloes and can be found in the autumn. These fruit are not generally eaten by humans as they are a very bitter fruit, but are used for making wine, sloe gin and preserves. This fruit is a great food source for birds and is a favourite food of many moth larvae. The shrub itself is a good, safe hiding place for small birds due to its dense thorny branches.

Photographs courtsy of the National Botanic Gardens - special thanks to Grace Palsey

For more information on trees see the links below:

Links for Trees and Plants Tree Council of Ireland Coillte CRANN Forest Friends Irish Seed Savers Irish Timber Growers National Botanic Gardens National Council for Forest Research and Development Native Woodlands Scheme - Forestry Service Woodlands of Ireland Just Forests -Global Forest Conservation  Irish Wild Flowers


©2007 Department of the Environment, Heritage and Local Government