Chilly, crisp and dark - winter is finally here
December is a time for reflection. Chilly, crisp and dark days herald the true beginnings of winter. The bare bones of the garden are exposed. Few leaves and fewer flowers, allow the structural plants to dominate. Evergreen plants, strong winter stems and attractive barks can bring welcome colour to an otherwise quiet, grey scene.
In the garden
Trees with ornamental bark, often hidden by strong leafy growth the rest of the year, can shine in the winter and add to the year round interest of a garden. Paperbark maple, Acer griseum with its flaky peeling bark shining a rich yellowy orange, coral bark maple, Acer palmatum ‘Sango-Kaku’ with deep pink stems, Himalayan birch, Betula utilis var. jacquemontii with brilliant white bark, Tibetan cherry, Prunus serrula with a rich red glow in low light and river birch, Betula nigra, with peeling grey-white bark becoming pinky orange in the wintery sunshine.
Shrubs too can display colourful stems in winter; dogwood, willow and bramble all have many varieties with brilliant coloured barks. Rubus cockburianus has a ghostly white bloom over arching purple stems, Cornus alba ‘Kesselringii’ has deep purple black stems and Cornus sanguinia ‘Midwinter Fire’ has stems which from base to tip change through yellow, orange and red to pink. Willows grow well in damp soils, Salix ‘Yelverton’ has orange yellow stems and Salix alba var. vitellina ‘Britzensis’ vivid scarlet stems.
Holly and mistletoe, the characteristic Christmas plants, are favorites in December. Mistletoe is a semi parasitic shrub that grows on other trees, taking water and nutrients from the host. The seeds are sticky and dispersed by birds that either smear off the remains or excrete droppings onto a branch. The seed grows roots, which pierce the bark and feed from the tree, growing into rounded balls, clearly visible on the bare branches in winter.
Hollies or Ilex have a variety of leaf colour, shape and berry colour. Male and female flowers are grown on separate plants so to be sure of fertilisation and colourful berries you will need to plant one of each sex close together. Ilex aquifolium ‘Handsworth New Silver’ has dark green leaves, edged with cream and bright red berries, Ilex aquifolium ‘Pyramidalis Fructu Lutea’ has dark green leaves and yellow berries. Ilex x altaclerensis ‘Golden King’ has oval variegated leaves with large red berries, Ilex x altaclerensis ‘Lawsoniana’ has green leaves with central splashes of yellow and pale green and bright red berries.
Evergreen shrubs give interest and provide welcome shelter for wildlife in the cold months. Denser shrubs will provide the best shelter. Lauristinus, Viburnum tinus has shiny, dark green leaves, clusters of pale pink flowers throughout winter, followed by black berries. Ivy is useful protection for both insects and birds, it can provide nectar as late as December and its winter fruiting berries provide food for blackbirds and thrushes as well as hibernation sites for butterflies.
Winter pruning apples, pears, currants and gooseberries
Many people are apprehensive of and confused by pruning, but with sharp secateurs, loppers and pruning saws, and frequent checks on the overall shape, it’s not a difficult task. The aim in pruning bush or standard fruit trees and currant bushes is to create an open, vase shaped form where air can freely flow between branches and stems, to increase fruiting, to help prevent congestion and the potential build up of disease.
For all trees and bushes begin by cutting out the crossing, dead, damaged and diseased wood. For apples and pears, next shorten the previous year’s growth on the main branches by one third, leaving the laterals that grow off the main branches unpruned to develop fruiting buds the following year. Finally cut out shoots growing towards the centre and any crossing or congested sideshoots. Older trees develop fruiting spurs; short, woody growths on the tips of branches, thin these out if they become congested.
The winter pruning of gooseberry, red and white currant bushes is the same. As with the trees, cut out crossing, dead, damaged and diseased wood. Next prune all side shoots to 1-3 buds from the base of the stem, finally shorten the branch tips by around ¼ cutting back to an outward facing bud. If you don’t have room for a leaf mould bin you can collect leaves in hessian sacks or bin liners, aerated with a few holes. Add a sprinkling of water to the leaves and tie up. Leave in a shady corner till the following autumn and check the leaves are well rotted before spreading under trees and shrubs or under woodlanders in the shady parts of the garden.
Planting deciduous trees and shrubs
December is a good time to plant trees and shrubs but don’t plant when the ground is waterlogged or frozen. Soil preparation is key to healthy establishment and growth so spend time getting this right. First dig over the soil to the depth of the rootball and over about 1 m square, at this stage you can incorporate some well rotted stable manure to improve the soil structure. Tease out the roots of containerized plants and spread out the roots of bare root plants. Dig the hole to the depth of the roots and about three times the width of the spread. Soak the plant or pot well for 20-30 minutes before planting. Place the tree or shrub in the hole making sure that the root flare area will be level with the top of the soil. For larger or heavy trees and shrubs a stake may be necessary to prevent the plant toppling over as it establishes, put this in before back filling. Fill in the hole, making sure to lift and shake soil between all the roots and tamp down gently to fill any air pockets. If a stake has been used tie the plant to the stake in an upright position.
Planting hedges and trees to trap pollution
If you live in a heavily polluted area, planting suitable trees and shrubs that can trap pollution can be very effective in freshening the air. Planting street trees, beside a playground, food growing area or front garden can help by removing some of the pollution from the local environment. Plants collect polluting particles on their surface areas, particularly evergreens with rough leaves or dense canopies. Hedges, and densely planted shrubs, mixed with trees, create the best pollution barriers. Plants like yew, Taxus baccata, lauristinus, Viburnum tinus, western red cedar, Thuja plicata, cotoneaster, hornbeam and whitebeam, Sorbus aria have been shown to work well.
Plant propagation, hardwood cuttings
Hardwood cuttings taken in December will provide new plants, ready to be planted out by next autumn. At this time of year you can take cuttings from both deciduous and evergreen woody plants.
Chose strong and healthy looking woody stems, about the thickness of a pencil. When taking cuttings from deciduous shrubs wait until the stems are bare, make a horizontal cut just below a node at the base - the place where the stem widens and new leaf buds are beginning to show- and a diagonal sloping cut just above a node around 20cm further up the stem. Evergreen cuttings are taken in the same way, before removing the leaves from the lower half of the stem.
The cuttings can be grown on either outside in a trench or in pots. First prepare the soil. Outside, add sand to the soil, to create a well-drained growing medium and make a slit wide trench, or fill deep pots with a half and half mix of multipurpose compost and grit. Dip the cut bases into a hormone rooting product and insert in the trench or pot. Insert around ¾ of a deciduous stem and around ½ of an evergreen stem in the soil. Keep pots in a sheltered spot or cold frame and firm in well. Water gently at first but make sure the cuttings are kept well watered as the weather becomes warmer and drier in the spring and summer.
Pruning trees and shrubs prone to ‘bleeding’
Sap carries nutrients and water through a vascular system to all parts of a plant. Some plants bleed profusely from pruning cuts or wounds. In most deciduous plants the sap production decreases in autumn and winter as the plant becomes dormant, in late winter and early spring the rising sap carries nourishment to the swelling leaves and buds. There are some plants where the sap starts to rise early, leaving them vulnerable to excess bleeding during late winter pruning. For those it is best to prune earlier in the seasonal cycle, in December.
Trees and shrubs that benefit from December pruning include grape vines, Vitus, maple, Acer, walnut, Juglans, birch, Betula, mulberry, Morus and lime, Tilia. Choose a cold, bright day and head out with clean, sharp secateurs.
Gardening tasks in December
- Leave grass uncut, the stems will provide hibernation sites for beneficial insects.
- If there is snow, shake it off trees and shrubs to prevent the extra weight bending and breaking branches and stems.
- Check the condition of any plants needing winter protection.
- Plant deciduous trees and shrubs.
- Check the condition, ties and stakes on any newly planted trees and shrubs.
- Winter prune apples, pears, currants and gooseberries.
- Prune climbing roses and ornamental vines.
- Prune plants prone to bleeding from cuts such as maple, Acer and birch, Betula.
- Take hardwood and root cuttings.
- Wash, dry and stack your seed trays, pots and unused containers ready for the spring planting season.
- Provide food and water for birds, make sure feeders and bird baths are cleaned regularly and clear of ice.
- Make a hole in icy ponds with a kettle of hot water to provide oxygen to the water and a place for mammals and birds to drink from. Don’t smash the ice as this can harm some pond living creatures.