It is June at Shibui Bonsai and that means winter. We have had a few light frosts so far this season but this morning was probably the coldest yet.
Here in Australia we do not have to contend with really severe cold that growers in some other areas get. My cold hardy trees stay outside without any protection all winter without any ill effects, in fact I think it might even be good for them. Low temperatures help to induce some trees to flower better and I hope that some of the pests and diseases will also be killed during cold weather. My ficus, which are NOT cold hardy, live in the unheated poly igloo which provides enough protection to get them through the winter here.
Winter is the time I do most of my pruning on deciduous trees because, without the leaves it is easier to see the structure and placement of branches and twigs.
I also start repotting some of the hardier trees. I agree that spring, just before budburst, is the ‘best’ time to rootprune but I have too many trees to get all my repotting done in the few weeks of spring so I had to look for other safe times to spread the load. When I realised that nurseries were stocking bare rooted fruit and ornamental trees right at the start of winter it occurred that the commercial growers must be digging these from the growing beds at the end of autumn in order to get them to the nurseries so early. The vast majority of these trees survive being dug early, transported then heeled in in damp sawdust all winter so I could not see why my bonsai would not tolerate similar treatment, especially when I am giving them much better aftercare than any bare rooted fruit tree ever got.
We also start to dig the field grown stock from the growing beds and preparing them for potting up for sale or to go back into the ground for a few more years to improve further.
There is no need to fertilise during winter as the trees are dormant so they cannot use the fertiliser which just gets leached out of the pots by winter rainfall and may contribute to environmental problems when it runs into waterways and soaks into the ground.
I do find that frosty weather dries the potting mix so if we have not had rain for a week or so I start to check that the pots are still moist and water if necessary.