Weather and the Gardener
Whatever the weather in December may be, mild windy and wet or cold foggy and dry, one thing is certain - the nights will be long and there will be little daylight. Light is very important to plants and does much to regulate their stages of development.
The need for adequate light is often forgotten by gardeners who use glass or plastic cover to extend the growing season, and few amateurs use any form of additional artificial lighting. Therefore it is worth considering what any form of transparent cover will, or will not do.
All forms of cover reduce the incoming light, so glass and plastic should be kept as clean as possible.
Trees and Shrubs
Berries may persist on some plants if not eaten by birds and colourful stems of shrubs such as cornus (dogwoods) also brighten the scene. Plants which flower reasonably well include Prunus subhirtella 'Autumnalis' (autumn cherry), Erica carnea (heather) varieties, hamamelis (witch hazel), Jasminum nudiflorum (winter jasmine), Lonicera fragrantissma (shrubby honeysuckle), and several forms of mahonia and viburnum.
Soil Preparation and Planting
Any ground not already prepared for trees, shrubs and climbers should be dug this month. The surface can be left rough to be broken down by frost and snow.
Plants that were delivered lates, or which have been stored or heeled in, should be planted into previously prepared beds as soon as the weather is mild and the ground not frozen, too wt or snow covered.
Roses
To prevent established hybrid tea and floribunda roses being damaged by snow or winds, shorten all stems with secateurs to about 75cm (2 1/2ft). Full pruning of hybrid tea and floribunda roses is carried out later in the winter.
Flowers
Top dress and prick in 130-260g per sq metre (4-8oz per sq yd) of bone meal - a long terms phosphatic fertilizer that encourages good root growth and strong plants - to nourish the border for the next two to three years.
Pot up spring flowering border plants in 12cm (5in) pots of rich gritty soil to bloom indoors. Suitable kinds are polyanthus, primroses, astilbes, Polygonatum multiflorum (Solomon's seal), small bergenias and Dicentra eximea. In a cold greenhouse or cool living room in good light they will flower weeks earlier and give you welcome colour for the bleak months.
Alpines
Extend interest by making a water garden close to your rock garden and linking the two with a stream 'powered' by a submersible pump. Line the stream channel with a thick, heavy polythene or butyl rubber and bury its edges beneath the soil. Sprinkle gravel over the stream bed to sparkle as water passes over it in sunny weather.
Bulbs
String black cotton over beds of crocuses being pecked at by birds, or spray the area with a bird deterrent.
Prepare sites for giant woodland lilies sich as Cardiocrinum giganteum: take out a hole 60cm (2ft) deep and square and enrich the bottom half with well rotted manure. Top with soil and set the bulbs shallowly, with their tops just beneath the soil.
Vegetables
All growth will have stopped outside, but it should be possible to continue harvesting cabbge, celery, leeks, parsnip, Brussels sprouts and possibly cauliflower. The latest sowings of carrot and swede should, by now, have produced usable roots and these should be lifted and stored.
From store, use beet, carrot, potato, shallot, swede, turnip and possibly marrow. Check on stored crops and take out any which are not keeping.
Outside, increase the soil cover round celery, and under frames or cloches plant out seedlings of the latest sowings of winter lettuce.