Check or install winter protection frames for fleece, or straw.
Check greenhouse heaters are working.
Insulate, drain, or turn off outside taps.
If you have a pond, float a ball to ensure a frost-free zone to allow oxygen into the water for fish.
Prune apple and pear trees (not espaliers).
Prune Acers, Birch and Vitis before Christmas to ensure the wounds heal.
Lift and move shrubs.
Take hard wood cuttings of Viburnum, Carpinus, Philadelphus and Weigela.
Lay traps and bait for vermin in stores and greenhouses.
Reduce watering of house plants.
Jobs for December
Sowing and planting
Alpines can be sown from seed this month. They need a period of cold to break the seed dormancy. A sheet of glass can be positioned over the sown area to protect it from excessive wet. Alternatively, the seeds can be stratified in the fridge, for sowing next spring.
Cutting back, pruning, and dividing
Continue to cut back faded herbaceous perennials and add them to the compost heap or alternatively leave these until spring so that they can be used as winter homes for insects.
In mild areas, and during dry spells, you can still lift and divide herbaceous perennials. This will increase stocks and revive tired, or poorly flowering clumps.
Root cuttings can be taken from now. Papaver (perennial poppies), Verbascum (mullein) and Phlox are suitable examples.
Helleborus niger (Christmas rose) blooms can look unsightly when splashed with muddy raindrops. Bark chip mulch will reduce this splashing effect, and cloches can always be used where practical.
Clear up weedy beds ready for spring mulching. Order bulky organic matter (e.g. well-rotted farmyard manure, or mushroom compost) for use as a soil improver or mulch.
Protect for the winter
Check on tender plants outdoors to ensure winter protection is still in place, especially after storms. Raise patio containers onto feet or bricks to avoid them sitting in the winter wet.
Large tubs that are at risk of cracking in the frost should be covered with bubble wrap, hessian, or fleece, to insulate them over the winter. Tender plants and pots can be brought into the greenhouse or conservatory if not done so already. Even in mild areas, the winter usually gets much harder after December.
Apply a mulch to protect plants that are borderline hardy.
If you have not already done so, finish the autumn tidy-up of leaves from beds and borders. It is especially important to clear leaves and debris from alpines, as they will die off if covered in damp for any length of time. Bare patches can be covered with gritty compost to encourage the re-growth of surrounding clumps into that area. Keep tubs and containers tidy too, cutting back and removing debris regularly. They can be mulched with compost.
Improve the drainage of heavy clay soils by working in plenty of bulky organic matter, such as composted bark.
Order seed catalogues, if you have not done so already, to select next year’s bedding and perennial choices. You will have more chance of finding all your choices in stock if you order well before the spring.
Pest and disease watch
Look out for Botrytis (grey mould) on spent herbaceous plants and remove affected growth. Otherwise there is a risk that fungal problems could spread to healthy plants.
Hellebores can be at risk of diseases such as hellebore leaf spot.
Watch out for downy mildew and leaf spot on winter pansies.
Sometimes daffodils can come up very early, even before Christmas. Enjoy them, but be aware that they too can succumb to fungal problems, such as narcissus leaf scorch.
Look out for crown rot and brown rots (sclerotinia) on died down perennials, especially if you are on a clay, or poorly drained soil.
Antirrhinum rust and delphinium black blotch, as well as sclerotinia, will lay dormant and re-infect plants when they come up the following year. It may be necessary to replant new specimens in another place if the problem is severe.
Be aware that many diseases will hide in the soil, or on plant debris.
Trees and shrubs
Planting and moving
Protect newly planted trees, hedges and shrubs from cold winds and frosts, which can loosen and lift the roots. Gently re-firm them in if you notice this problem, and erect a temporary netting windbreak if there is no natural shelter. Thick dry mulches will protect the roots from cold. Branches can be covered with fleece, or even packed with dry straw and then covered with fleece, for tender plants. A wooden frame with clear polythene stretched over it does a similar job for evergreens without blocking the light, but don’t let the polythene touch the leaves, as condensation could freeze or cause rots.
Continue to plant bare-root deciduous hedging plants and trees. Put rabbit guards around newly planted trees and shrubs to protect the bark from damage.
Plant roses, but avoid areas where roses were previously grown as this can lead to problems with replant diseases.
Move established deciduous trees and shrubs, provided the ground is not frozen or soggy.
Pruning and training. Tie wall shrubs and climbers onto their supports to protect them from wind damage.
Pruning and renovation of many deciduous trees, shrubs and hedges can be carried out from now throughout the dormant season. It is easier to see what you are doing when the branches have no leaves. Suitable examples are: Fagus (beech), Corylus (hazel), and also roses. Ensure any pruning of Acer and Betula is completed before the end of the year to avoid bleeding of sap from cuts.
* Exceptions are evergreens and tender plants (these are best left until spring), and Prunus species (e.g. ornamental cherries, plums and almonds), as these are vulnerable to silver leaf disease when pruned in autumn or winter.
If your trees are too large for you to manage the pruning alone, then you may need a tree surgeon. Otherwise take care not to damage the tree when sawing off thicker branches.
Take hardwood cuttings of ornamental shrubs such as Berberis, Buddleja, Salix, Forsythia, Ligustrum and Rubus. Many deciduous climbers can also be propagated in this way (e.g. Fallopia and Lonicera).
Check hardwood cuttings taken last year. They may need planting out or potting on.
Christmas tree care
Prevent premature needle drop on your Christmas tree by choosing a pine (Pinus) or fir (Abies) tree instead of the traditional Norway spruce (Picea abies); these hold their needles for longer. Avoid placing your tree near sources of heat such as a fire or radiator. Cut trees will last longer if stood in a bucket of water or a stand with a reservoir. Saw off the bottom 5-7.5cm (2-3in) of trunk to allow the tree to drink freely.
Take note of the most colourful dogwoods (Cornus), Salix and white-stemmed Rubus shrubs when visiting gardens open to the public, or in garden centres, and consider planting them yourself for a winter display.
Packing the branches of tender deciduous trees and shrubs with straw or bracken, and securing this with fleece and ties, will protect them from frost.
Check tree ties and stakes. Replace, tighten, slacken or remove as necessary. Remove weeds from around the bases of young trees.
If there is snow in your area, then you may need to brush it off the branches of conifers, climbers and light-limbed shrubs and trees. Heavy snowfall can splay branches, break limbs and spoil the shape of the tree.
You may wish to protect a few holly berries from the birds, for use in Christmas decorations. Netting should do the job, but do leave some uncovered for winter wildlife.
Ponds - Beware ice
Use pond heaters to keep ponds from freezing over, as these conditions can be fatal for fish and other pond life. There are other precautions you can take to prevent your pond freezing over, if you do not have a heater. To make a hole in frozen ponds, hold a saucepan of hot water on the surface until melted through. Do not crack the ice, as this is harmful to fish.
You may wish to make your pond more wildlife friendly.
Deter hungry herons from fishing using nylon strings strung across the edges of the pond, at least 15cm (6in) from the ground and 15cm (6in) in from the edge of the pond.
Continue to rake out fallen leaves or shake off those that have gathered on protective netting.