January is the coldest month of the year, days are pleasant and night times are cool. It is a good idea to wrap trunks of young citrus with burlap to protect from frost. If leafage gets frost burn, leave dead foliage on to protect from further damage. Add a little compost and a thick layer of mulch to protect the tender new growth. If the ground is workable and not too wet, now is an excellent time to turn the soil. Not only will this expose insect eggs to the effects of winter and hungry birds, the cold will help to break apart heavy clods of dirt. Continue to plant spring annuals, shrubs and trees. The time is right to transplant hardy plants and begin pruning roses and deciduous trees. Start to apply crabgrass control to get an early jump on it spreading. Finally, extra time this month might well be spent getting the garden tolls ready for spring. Sharpen and oil tools such as shovels, shears, mowers and the like. Hey! How about a fresh coat of paint on the wheelbarrow?
As an irrigation tip, keep above ground irrigation equipment such as garden hoses, irrigation valves and pipes insulated or covered to help protect from cracking due to cold and sun exposure.