January is a good time to sow seeds of Begonia, Lobelia, Salvia and Pelargonium in a heated greenhouse or propagator to provide early plants. Sweet peas also can be sown this month. You have a last chance to sow seeds that need frost in order to germinate, such as native tree and shrub seeds, alpine plants. Plant lily bulbs in pots and in borders during mild spells.
Cut off old leaves of hellebores that produce flowers from ground level and cut away some Iris Unguicularis leaves in order to expose the flowers. Root cuttings (Papaver, (perennial poppies), Verbascum (mullein), Acanthus and Phlox) can be taken now.
Start cutting back grasses and other perennials left for winter interest. In mild areas, and during dry spells, you can still lift and divide herbaceous perennials.
Rake up any winter debris and leaves off your borders to keep them tidy. Clear up any weedy beds ready for mulching in the spring. Keep tubs and containers tidy by cutting back and removing debris regularly. They can be mulched with a compost or grit.
Raise patio containers onto feet or bricks to avoid them sitting in the wet. Your garden tender plants should be taken into the greenhouse or conservatory.
Protect non-frost-proof containers (terracotta pots, etc.) with bubble wrap, hessian or fleece, to prevent them from cracking in cold weather.
Stock up on store cupboard items such as string, stakes, and canes for use later in the year.
Inspect stored tubers of plants such as Dahlia and Canna for signs of drying out. it is important not to let the tubers become bone dry, or they will not grow next season. Keep alpine houses well ventilated and remove dead leaves from around basal rosettes in order to prevent rotting.
Do not forget to protect new sweet pea plants from aphids. Check autumn-sown sweet peas growing in cold frames, and apply mouse and slug controls if needed.
Watch out for downy mildew and black spot on winter pansies. Remove any infected leaves and destroy badly affected plants.
Look out for rots (such as crown rot, sclerotinia, Delphinium black blotch and black root rot) on died down perennials. Check stored bulbs carefully for signs of rot and remove affected bulbs. Hellebore leaf spot can also be a problem on old foliage.
Continue to plant bare root deciduous hedging plants and trees. Stakes should be put in place before the root ball to avoid damage to the roots. Avoid planting roses in the areas where they were previously grown as this can lead to replant diseases.
Move established deciduous trees and shrubs if the ground is not frozen or waterlogged. Check tree ties and stakes on established plants. Replace, tighten or slacken them where necessary and firm back newly planted trees and shrubs if they have been lifted by frost or strong winds. Thick dry mulches can protect the roots from cold. Branches should be covered with fleece, or firstly packed with dry straw and then covered with fleece, for tender plants. A wooden frame with clear polyethylene stretched over it does a similar job for evergreens without blocking the light, but don’t let the polyethylene touch the leaves.
Remove weeds from around the bases of young trees. Brush the snow off the branches of conifers, climbers and light-limbed shrubs and trees. Heavy snowfall can spray branches, break limbs and spoil the shape of the tree.
Pruning and renovation of many deciduous trees, shrubs, and hedges can be carried out from now throughout the dormant season. Take care not to damage the tree when sawing off thicker branches.
Prune Wisteria – cut back the side shoots shortened by summer pruning to two or three buds. Avoid cutting off flower buds. Tie wall shrubs and climbers onto their supports to protect them from wind damage. Ornamental vines, ivy, Virginia creeper and Boston ivy also can be cut back now.
Take hardwood cuttings of ornamental shrubs (such as Cornus, Salix, Forsythia, Weigela, Escallonia, Rosa, Ribes, Chaenomeles, and Elaeagnus) and many deciduous climbers (e.g. Fallopia and Lonicera).
Check hardwood cuttings taken last year. Seeds of berrying trees and shrubs can still be sown.
Put rabbit guards around newly planted trees and shrubs to protect the bark from rabbit damage. Inspect sick-looking box and holly trees for signs of blight. Phytophthora root rots can cause dieback on mature trees and shrubs. Wet winter weather and poorly drained soils are likely to encourage this problem.
Coral spot is often noticed once the leaves have fallen from deciduous hedges, shrubs, and trees. This problem can be connected with poor ventilation and congested un-pruned twiggy growth. Bracket fungus on trees is also visible at this time of year. Check for damage or cankers on deciduous trees while stems and trunks are readily visible. Prune out torn or damaged branches to prevent disease infection.
In the mild weather, you can lay a new turf or repair hollows and bumps in an existing lawn.
For the latter, make an ‘H’ shaped cut in the turf, peel back the grass and either fill the hollow with loam or scraping away the soil from a bump. Re-lay the turf, press it into place and pinch the cut edges together.
Repair lawn edges, especially around flower and shrub beds, with curves cut from other areas of the garden. Consider laying stepping-stones through dieback lawn and do not to walk on frosty grass as this will burn or scorch the grass. After that, it will appear to be black and have brown footprints after a while.
Watch your lawn for signs of waterlogging.
If you missed the opportunity to carry out autumn lawn maintenance, then you can still remedy the situation by spiking the lawn with a garden fork or mechanical aerator. After that, fill the holes with a mixture of sharp sand and loam, brushed in using a stiff broom.
Mole activity will increase this month due to mating and nest (fortress) building. Remove the largest hills and re-form before overseeding in spring. Keep brushing away worm casts, as they can be troublesome at this time of year.
Fusarium patch (snow mould) and Algae may also be a problem in wet weather.
Monitor the water level of your pond, as hard frosts can cause defects in the liner and in concrete structures. Rake out fallen leaves or shake off those that have gathered on the protective netting. If necessary, use pond heaters or place floats on the surface of the water to keep it from freezing over as this can be fatal for fish and other pond life.
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 can treat timber structures, including garden furniture, with wood preservative and stain in dry spells and in a well-ventilated space. Ensure all standpipes and irrigation lines are drained to avoid damage from water freezing in them.
Put lagging around outdoor taps to prevent freezing and to enable use throughout the winter.
Wash out your old pots by using a product such as Citrox (to reduce bacterial and fungal spores without causing toxicity to plants).
Check and repair pergolas and arches if needed.
Now is also a good time to consider installing garden lighting, water pipes, and drainage. Remove algae from paths if they start to become slippery, beware of using too much salt as this could damage your plants.