Why winter is a great time to plant trees
The winter months (December to March) are a great time to plant trees.
In the winter, trees will either be dormant or be approaching dormancy. This means they are not actively growing. You could say your tree is resting.
But while the above-ground parts of your tree seem to be asleep and inactive, the roots are still performing the essential life processes, albeit at a minimal rate. This means, when you plant your tree in winter, during mild spells, they will begin slowly spreading and expanding their roots in search of water and nutrients. By the arrival of spring and warmer weather, your newly planted tree will have grown a substantial root network. This will help it cope with the oncoming acceleration of growth. Winter helps new trees with this preliminary root expansion by keeping the soil moist due to regular rainfall.
Winter is also beneficial because your newly planted tree will not be competing against lots of weeds. In spring and summer these fast-growing competitors will aggressively steal the water and nutrients your new tree badly needs. New trees are particularly vulnerable to competing plants in their first year. But in winter most of these weeds will be absent, so your tree can start to grow its roots freely. Once they are established, your tree can hold its own against weeds more effectively.
Trees can of course be planted any time of the year, even in the middle of a hot dry summer. However if you do this it is critical that you regularly water your new tree because the soil is likely to be dry and the tree is already actively growing. They will require a full watering can every other day if the weather is going to be hot and dry. Lack of water is one the main killers of newly planted trees.
Image courtesy of Chulmin Park