Broad-leaved trees shed their leaves in autumn, because they would lose a lot of water in winter at a time when growth is not adequate to draw water from the soil. The trees would die in frosty weather.

Some evergreen conifers adopt a different strategy, such as pines, spruce and fir, by making narrow needle-like leaves that are coated with wax to avoid moisture loss. But tough deciduous trees, such as birch and willow, can survive in colder places than even needle conifers.

Broadleaved evergreens only shed leaves intermittently and keep most of their leaves over winter, but these are natives of warm climate, such as griselinia and pittosporum, and succumb to hard frost, proving the value of being deciduous.

Trees do not waste anything. Before the leaves fall, much of the nutrients are withdrawn, all the soluble sugars and green chlorophyll. These are stored in the roots, trunk, branches and bark to keep the tree alive in winter and to power new growth in spring.

Trees have a green layer in the skin that continues to photosynthesise. The other pigments, yellow and red, are not as mobile and they remain in the leaves, giving autumn colour on the tree. Not as highly regarded, but also very beautiful, is the carpet of fallen coloured leaves. But the richly coloured leaves soon change to brown as they dry out.

Fallen leaves are not wasted either. In summer, trees use their leaf canopy to cast shade on lower-growing plants, such as grass and weeds. When leaf fall occurs, the whole array of leaves is dumped on the lower plants in a strategy to deny light and kill them. Some tree leaves, such as walnut, have chemical compounds to interrupt growth, while oak foliage is full of tannins.

The autumn leaves generally fall directly onto the root area of the tree. This means that much of the root zone gets an annual natural mulch of nutritious leaves. These break down due to the activities of bacteria and fungi.

In some cases, the fungi are symbiotic with the tree and return nutrients from the soil to the tree, and the tree roots also pick up nutrients directly. Earthworms and insects help to mix rotting leaves back into the soil, improving its aeration. Humus increases and moisture is better retained in summer.

To reduce the effort of leaf removal, let the leaf litter lie where it falls under trees or shrubs. Even if there are some weeds present, these can be controlled when the leaves have rotted over winter.

Leaves must be removed from lawn areas, and this can usually be done with the lawnmower, especially a ride-on. Try to take leaves off in stages, rather than allow a wet layer to build up. Leaves must also be taken off tarmac, concrete, gravel or any other paving, paths or driveways, because they cause staining and encourage moss and weeds to grow when they decompose. For most country gardens, a petrol-engine leaf blower is essential, used on dry leaves.

Leaves taken from the lawn area and driveways can be composted in a heap, covered with a square of old carpet. The grass mixed in hastens the breakdown of leaves. A big pile of leaves breaks down to a small heap of leaf mould. This can be used as a mulch or as a soil improver when planting. Left for a second winter, it can be used as a peat alternative. It can be riddled to provide fine material for seed sowing, using the coarser stuff for potting.

Concerns about seedling damping-off diseases can be addressed by microwaving small amounts or sterilising with steam for 20 to 30 minutes in an old cooking pot. CL

Firethorn at its best!

Firethorn, or pyracantha, is exceptionally good this year. All over the country, the bushes are covered top to bottom with red, orange or yellow berries. It set a great crop of berries due to two years of good growing weather. Even if the weather was a bit wet for human activities at times, pyracantha and many other garden plants, especially shrubs, thrived.

In a less favourable sequence of weather, pyracantha might only furnish its stems with berries to half-way up their length and produce a lot of leafy growth instead. The sunshine-and-showers combination seems to have kept off the dreaded pyracantha scab disease, although this may be due to the more widespread planting of disease-resistant kinds. The berries look great with autumn leaf colours, and afterwards they brighten a garden, and provide food for birds!

Trees, shrubs and roses

This is the start of the traditional planting season for small wooded areas and shelter belts, using small whips. These are mostly sold as bare-root stock and are much cheaper to establish. Evergreens can still be planted but it would be best to wait until spring in an exposed site. Rose bushes can be planted now.

Lawns

Grass growth has been good all summer with enough rain except for one week or so. Carry out mowing if possible. Repairs to a damaged lawn can be carried out and humps and hollows fixed. Although seed will be slow to germinate now, it can still be sown. If lawn moss is evident, apply sulphate of iron.

Flowers

If there are any spring bulbs still to plant, they should be planted without delay. Most perennial flowers can be lifted and divided or new specimens planted, but do not do this if the soil is wet and sticky. Dahlias and cannas may need to be covered or lifted. Containers can still be planted with spring bedding.

Fruit, vegetables and herbs

Established fruit trees can be pruned, with the exception of plum and cherry trees. The vegetable area can be tidied up, and weeds should certainly be controlled. Plant fruit trees and bushes of all kinds in the coming weeks. Apples, pears and plums are easy to grow in a good well-drained soil with a sunny aspect.

Greenhouse and house plants

Tidy away old tomato plants. Water house plants sparingly and do not stand the pots in saucers of water. All debris and dead plants should be removed and pots and trays can be washed. Water lightly, if at all. The glass should be cleaned. Check for pests such as greenflies that can cause a lot of damage now.