"Winter has me in its grip
Think I'll take a summer trip
On a sunny sailing ship
Where the shells lie in the sand"
Winter has me in it's grip
Winter causes more worry to the bonsai enthusiast than any other thing I know. Those of us who have species that originate in the temporate zones of our planet, will if new to the art begin to get concerned as Autumn appears, however with a few precautions winter need hold no fear.
As I've said in other parts of the Primer the last thing you should do, is to bring a temporate species into a heated, and lit environment, over winter "because they're so delicate!". They're not!.
Let's look at why a tree will die over winter, off hand I can think of two reasons, both involving water. Firstly if you have a poorly drained compost this may cause the roots to rot away. Secondly, and perhaps more commonly, freezing conditions. Throughout the year, wind causes water to evaporate away from your trees, in the same way that your washing dries in the line, if kept outdoors this water can be replaced if the compost is wet, however if the compost is frozen solid, water removed from the tree cannot be replaced and the tree is "freeze dried". Trees in the ground have root systems that go below the frozen soil, so do not suffer in the same way.
In Autumn, sugars are withdrawn from the leaves of deciduous trees, to be stored in the roots and trunk. This sugar acts as an antifreeze, protecting deciduous trees over winter, however conifers are at greater risk than deciduous trees, because they retain their foliage, giving a greater surface area for water to evaporate from, while not producing as much sugar as in the growing season.
|So what can you do to protect your trees in the worst conditions?. Try to get them into shelter, this can be an unheated glasshouse, garage or other outhouse. If you don't have one and your trees are not to large, put them in a plastic bag, and leave them in a sheltered place outside, removing them from the bags as soon as the freezing spell is over. Remember it's the wind that kills them, not the cold.||
A few days of snow will not harm your trees, if sheltered from the wind.
Inspect your trees regularly, they can still dry out, and die if neglected.
They can be kept in total darkness while dormant.