One of the trickiest areas of raising a Bonsai is the question of repotting.
Most Bonsai keep growing throughout their lives -unless deliberately stunted- and will periodically need to be transplanted into larger accommodations if they're going to remain happy and healthy. Of course, this is rough on the Bonsai. Trees never replant themselves in nature, so it's up to you to ensure there's as little trauma to the Bonsai as possible.
The question of whether it's better to repot in the fall or spring comes up often, and with autumn arriving soon, it's a question some Bonsai owners may be asking themselves. So let's take a look.
Bonsai Care: Fall vs Spring Replanting
The short version of the debate boils down to this: If you repot your Bonsai in the fall, it's already getting ready to go dormant for the winter and won't be as affected by the transplant. The roots should have time to heal before spring comes. The downside is, there's more chance of something going wrong, especially with older trees.
On the other hand, Spring transplants are generally a bit safer, since it's prime growing season and the tree will be able to quickly rebuild its root system. The tradeoff is that this may greatly lessen its above-ground growth for the following year, as its most productive growing months will be focused on the roots.
Either method can work if you follow proper repotting techniques.
If you're considering a fall repotting, here are more aspects to consider:
1 - Your specific breed
Every breed of Bonsai is different, and can react to the seasons quite differently from other kinds. It's a good idea to check care sheets for your specific breed of tree, to ensure it doesn't have a strong preference for one season or the other.
2 - The age of the tree
Broadly speaking, the older the tree is, the better it is to wait for spring for replanting, just to be safe. Older, established Bonsai don't deal as well with the shock of a transplant. So the combination of that and the onset of winter can sometimes be too much for them.
3 - The condition of the roots
Most replanting's -especially with older Bonsai- involve pruning away roots which are too long, thick, or old to function effectively. This, however, also adds to the stress on the Bonsai. Fall plantings are better in situations where you'll be doing relatively little pruning to the roots.
4 - Your local climate
Simply put: If it's an outdoor tree and freezing weather is likely, do not replant in the fall if at all possible. Bonsai deal poorly with freezing weather to begin with, so the combination of repotting stress, pruned roots, and cold weather can easily do great harm to a tree.
5 - Soil quality
If you're doing a fall repotting, be sure the soil is rich with extra fertilizer or vitamin additives. This will help keep the roots healthy and healing throughout the winter, ensuring it's ready for the spring bloom when the time comes.
Take Time and Care With Your Bonsai Transplants!
Much like surgery on humans, every Bonsai repotting carries a level of risk to the tree. However, also like surgery, it's often needed regardless of the risks. If you take time and do plenty of research before beginning the transplant, you and your bonsai will come through with flying colors