Summer to Winter - Transitioning your Bonsai November 15, 2020 15:15

In this article, we’ll take a look at the best way to transition your INDOOR bonsai trees from summer to winter.  To be clear, this is not about the care of your trees that will remain outside for the winter, it's about your trees that are not hardy enough to survive the winter.


We call them indoor bonsai, which is a little wacky since, truly, there is no such thing as an indoor tree, just trees that will survive indoors. 

Our winters are too cold for many bonsai

In Canada and much of North America, tropical and subtropical trees are brought indoors for the winter.  In Canada, virtually every tree sold on this site  must come in for the winter. There are really only two exceptions. Rosemary - which can winter outdoors in the warmest parts of Canada only - like southern BC and Juniper procumbens- which can winter outdoors in any part of the country, but must be protected. 


Let's focus on the trees that need to come inside. 

It’s October 2 today and if you still have bonsai trees enjoying the outdoor conditions, it's time to make the change.  In a perfect world, you will bring them indoors the same way you moved them outside - gradually. In the spring when you put them out, the biggest consideration was not to burn them. In the Fall, the idea is to minimize the shock they will experience from reduced light, warmer temperatures, and dryer air.  If you have the time, first bring your trees indoors just for the night and during the day move them to the shade.  You can keep this up for as long as the daytime temperatures are staying about 15C or 60 F, but check on what type of tree.  Chinese elms are fine, but the real heat lovers - like black olive will not be thrilled with the cooler days.

As you watch your trees, you’ll see signs that they are slowing down for the winter; no new growth, some yellowed leaves. Generally, winter is a time to rest and just about every tree needs a period of slowed growth. Trees from a temperate climate have their rest period triggered by shorter daylight hours and lowered temperatures


Pick your indoor spot, one that will provide as much light as possible, is away from heat vents and drafts, and out of the reach of kids and pets. Pick this spot with the exact tree you have in mind- for example, a ficus will appreciate steady warmth, but your Chinese elms and definitely your junipers will be best in a bright but cooler spot. 


Light: Even the best spot you have indoors might not be bright enough for your wintering bonsai. The easiest way to tell will be if you start to see weak growth- long stems, spindly with a longer than average internode ( which is the space between leaves). If this is the case you should probably supplement with artificial light, but don’t break the bank. Google indoor plant lights, there are many to choose from.

You’ll even notice a difference in the lighting if you keep your trees indoors year-round. The winter sun is lower in the sky, fewer hours of weaker light. 


Fertilizer:  This is pretty much unnecessary over the winter. At the most lightly feed your bonsai maybe once a month. Personally, I don’t bother. To me, Winter is just something I need to get through.


Water:  Water is a double-edged sword in the winter. On one hand, a tree that is semi resting does not need as much water so be prepared to cut back on your watering, not to the point of turning your bonsai soil into a rock hard desert landscape.   Be mindful that the water that got gulped up in the summer will not be used as quickly in the winter. Overwatering in the winter is a big problem, but don’t turn into a dribbler- when you water- water well, none of this shot-glass-a-day foolishness.

Now, here is the other side of the sword. Central heating is very hard on many plants. The air dries out and while you don’t want a lot of water going into the pot, you might need to use a pebble tray or spray the leaves to raise the local humidity.  Note- when you spray the leaves, get the underside, which is where the stomata are located, and if necessary cover the soil while you spray so that the water does not drip into the pot.


Oh ….and if you decide to go away during the winter- please don’t forget about your tree(s).