Preparing Your Bonsai Trees For Winter

The inevitable onset of winter, complete with freezing
temperatures and prolonged periods of wet weather can without proper
preparation cause a range of care issues for the bonsai enthusiast.

Trees from temperate parts of the world such as ours have
developed to cope with the cold weather by entering a period of dormancy.
Photosynthesis ceases in deciduous trees and slows to a trickle in evergreen

Proper preparation for winter starts during the autumn.
Trees produce sugars and carbohydrates which they use to stop themselves from
freezing.  It is important therefore to
make sure that your trees are well fed throughout the growing season in order
to give them everything they need to be ready for the cold.

Bonsai trees are generally very hardy and able to cope with
cold conditions. Generally it isn’t the cold which harms the tree. More damage
is usually done through dehydration. If the soil around the roots of a bonsai
freeze, the roots cease to function. They stop drawing in water. The top of the
tree however continues to release water. It is for this reason that prolonged
spells of freezing weather cause harm. This is can be made worse by freezing
weather coupled with strong winds  or strong
winter sun as it dries the trees out even faster. A lot of the potential harm
can therefore be removed simply by placing the trees into a more sheltered
position out of the wind or sun.

It is quite common for beginners in bonsai to want to over
protect trees by bring time into the house or into a heated conservatory. This
may result in the trees not actually entering the dormancy period. If this
happens the trees may carry out growing throughout the winter. This distortion
of the natural cycle will harm and can eventually kill the tree. The dormancy
period is essential to the health of trees from a temperate climate. Trees from
tropical parts of the world do not need this dormancy period as they do not
experience it in their natural environments. They can therefore be kept indoors
all year round.


When does the cold kill?

Generally speaking most trees from temperate parts of the world can be left unprotected until the weather gets down to -10. When it gets colder than this, protection is required. Exceptions to this include Trident Maples, Azaleas and Loropetalums. It’s important to research the kinds of trees hat you have to find out the degree of cold which they can stand.

A greenhouse is probably the best solution for protecting trees from the worst of the weather.

An unheated outbuilding can be used to protect deciduous trees. Since deciduous trees don’t need  light when not in leaf, they can be stored in shed, outhouses or garages when the weather gets cold.

Bonsai growers often construct benches in order to display their trees to best effect in the garden. Dropping the trees under the benches and then covering the bench top and sides with bubble wrap or something similar can be enough protection.

Another solution is to take the trees out of their bonsai pots and plant them out into the garden. This can provide the protection from the cold that the roots of the trees require. When the spring comes they can simply be potted back into the same pots.

As with planting bonsai out in the garden over winter, you can take the trees out of their pots and plant them into larger wooden boxes filled with garden soil.