|An article like this one is very limited in the amount of detail it can present on a subject. I would recommend that you read what Jonas Dupich of Bonsai Tonight started Dec 6th with a very good series on his blog (https://bonsaitonight.com/bonsai-blog/) to cover minute details on selection, watering, difference between healthy growth and vigorous growth, etc. It is written so that you can see it in your backyard and not with calendar dates (usually useless in other areas) or just like he does in California. It is written especially for beginners but most of the more experienced people will learn a lot too with a lot of pictures of the details.
It would be nice to be able to put your trees into 2 or 3 groups --outdoor trees, indoor trees, flowering trees. But nature has not done anything so simple. Some outdoor trees survive a lot of cold and others want to go dormant but can't have their roots frozen at all. Your job is to learn their foibles and work around them.
In general, you start by knowing that deciduous trees will go dormant and stay that way until something awakens them. Some are temperature sensitive, they go dormant when the temp drops in the fall and awaken when they get warm. These should be kept in a shady area to keep them cool. Others are sensitive in the change in day length: they go dormant when daylight gets short and will break buds when they sense the days getting longer. These are not so hard to care for.
Evergreens do not go fully dormant. They slow their processes but still use sunlight and some nutrients. However they still need their roots protected to prevent alternate freezing and thawing.
All outdoor trees, both deciduous and evergreen, need to have their soil moisture maintained and their roots protected from deep freezes. Since their sap flow is diminished, they cannot replace moisture lost to winds so they should be protected from a lot of wind. The plants can be protected by using ground heat to minimize the low and high temps. Set the pots on the ground and cover with mulch.
For those with tropicals care at this time depends on your facilities for giving them heat and light, the two things usually in short supply in January. I merely try to keep mine alive with the greenhouse at 50 degrees. Watch your greenhouse for the sun heating it too much. Be sure to monitor them for aphids and other problems. They do not get enough light to actively grow anyway. When the mame size shohin elms have had a month of dormancy I bring them into the greenhouse before the temps get to the lower twenties. They respond by starting growth so I have them for 'soul food' through January.
Styling can be done at this time but no repotting unless you are going to keep the tree from freezing after that. Repotting initiates new root development which is usually not very hardy. Repotting is 'best' done when the tree is waking up indicated by buds swelling before they show any green.
A better approach would be to study one or two thoroughly each day making notes on what needs to be done. January is an excellent time to start any remodeling projects that may be necessary. While the trees are dormant you have better view of the branch structure. Do any need to be moved or removed? Do any coarse branches need to be cut back to a smaller side branch for refinement? Do any long straight branches need wiring to give them motion? Does the tree really need a drastic redesign? You can also trim the twigs back while you have them there. You can also decide if that tree will need to be repotted this spring, is the present pot good or should you find a more appropriate pot for it?
Indoor trees will be using more water to offset the lower humidity. Soil will also be losing water faster through its surface. Be sure to watch the indoor trees for insect problems. Most plant insects love a controlled atmosphere like the indoors. Spider mites seem to get the most attention here because they do great in a low humidity and the lack of foliage spraying. Scale can be an easily overlooked source of trouble. There is usually more severe problems with plants that have been kept outdoors in summer than brought in without any treatment. Indoor trees need to be fertilized regularly and will require periodic trimming as they continue to grow through the winter.
Tender or tropical trees that are kept indoors will be using more water to offset the lower humidity. Soil will also be losing water faster through its surface. Be sure to watch the indoor trees for insect problems. Most plant insects love a controlled atmosphere like the indoors. Spider mites seem to get the most attention here because they do great in a low humidity and the lack of foliage spraying. Scale can be an easily overlooked source of trouble. The flat green kind can be hard to spot on the underside of leaves or tight against the stem. Indoor trees need to be fertilized regularly and will require periodic trimming as they continue to grow through the winter.
By John Miller - Reprinted From 2015|