There are few opportunities to work in the garden during December, as the soil can be too wet for digging. Lawns can be cut if they are dry and not frosted. During a dry, mild spell the lawn may be given a final raking and spiking to aerate the soil. December is a month for assessing the previous year’s work and planning next season’s displays. Remove perennial weeds that continue to grow throughout the winter and keep the beds tidy, removing any dead growth from perennials.
Make repairs to fences, paths and garden structures such as pergolas. Re-make and repair rock gardens and reduce overcrowded areas. If you live in a cold area, ensure that semi-tender subjects are protected by cloches. Providing that the soil is not saturated, deciduous shrubs and trees can be planted. If in doubt, wait until March. Where necessary, prune deciduous trees and shrubs.
Continue to plant fruit trees. Winter prune fruit trees as necessary and root-prune over-vigorous plums and cherries. Check grease bands, replacing any that have become damaged or covered with trapped insects. Provide a band to any trees not protected last month. Inspect all apples and pears in store, discarding any showing signs of decay or rot.
Greenhouse and Indoors
Check insulation in the greenhouse, if employed, at times of frost warnings and provide some heat even to the cold greenhouse. Keep a constant watch for fungal diseases such as rots and botrytis, both of which prosper in the damp, still air conditions often present in the winter greenhouse.
During clear days, open windows after any frost to allow the air to circulate. Take the opportunity to wash windows with horticultural disinfectant and to fumigate. Remove the dead stems of latechrysanthemus, spray the stools with water to encourage shoots for next year’s plants.
Indoor plants take on a far more significant role during the middle of winter. Bring inside the first of the forced bulbs – hyacinths, daffodils when the buds are clear of the neck of the bulbs. Place in a cold room and gradually acclimatise the plants to warmer conditions. The higher the temperature, the sooner the flowers will open and the sooner they will die!
Keep cyclamen in cool conditions 10–13°C/50–55°F maximum and ensure that they are in an environment of damp air by standing on a saucer filled with gravel and kept topped up with water. Azaleas should be kept at 7°C/45°F and moist at all times. Keep poinsettias at 15°C/59°F
and only just moist.
There will be little activity in the pond. The fish will not be taking food and amphibians will be hibernating. The main danger is of the water freezing over. If you have a pond heater, this should be switched on at night whenever there is a frost forecast. Should the pond freeze over, thaw a small area so that the toxic gases can escape to be replaced by oxygen dissolved from the air. This is done by placing a large can on the frozen surface and pouring boiling water into it to melt a small area. Never break the ice by striking with a hammer as this sets up shock waves in the water sufficient to kill the fish.
Before severe spells, lift parsnips. Check roots in store and onions to see that rot is not beginning to set in. If you failed to sow ‘Aquadulce’ broad beans during November, complete before the mid-month. Exhibition onion seeds should be sown in gentle heat towards the end of the month.