Ideas for Protecting Your Hardy Trees for the Winter

by Michael Rusnak
This is a mostly repeat of an earlier post from a few years ago, but then again getting trees ready for winter is an annual task, so  the ideas bear repeating.

Although pines and other winter hardy trees need their dormant period rest, because bonsai are kept in shallow pots there is a danger of your trees drying out, or being damaged during the winter months.  Without some protection, winter may weaken or damage a bonsai, or in some cases, an unprotected tree may not survive.  So some protection of the roots is prudent to keep the tree moist and healthy.

One way used by many of our club members, and that has worked for my own pines over many seasons is to heel the tree into the ground, along with a covering of mulch. Good spots for heeling in your trees include land scaped areas near the house.  Such locations give you the added benefit of wind protection from the house and in between shrubbery.  Plus you may already have plenty of mulch in these areas.
To do this I simply use a rake or garden hoe to pull away the landscaping mulch.  I like to carve a long shallow trench about as deep as the pots.  The long trench allows me to put up several trees at once and it seems much quicker than trying to heel them one at a time.  Once a shallow trench is cleared, just place the trees in the trench, and rake the dirt back in and around the potted trees.   Then pull some mulch back over the pots as well.  Below is a photo of some of my trees heeled in and covered for the season.

Trees healed into a shallow trench and covered with mulch

For most trees, I've typically heeled them pot and all, as long as the pot is of such quality that it can withstand the freezing without cracking apart.  If you are unsure about your pot, healing the tree into the ground works just as well if you slip you bonsai out of the pot.  From experience with, it is disappointing in the spring to bring the bonsai out of the ground and find that your pot has burst apart from the frost. So take note as to how the pot is going to hold up. 

I also like to use the tomato garden for some of my larger plants. It is close to the area where I keep a lot of the larger trees that I work with, so I don't have to carry them as far, and it seems to work real well for the bigger pines.  During a lot of winters, they stay coated with snow.

In the tomato garden

Another handy spot that I use are the window wells around the house.  In these spots, I put trees that are still in good-sized nursery pots.  The sunken well is handy and well out of the wind. Adding a little straw around the pots will also help protect the trees and is not too hard to clean out in the spring.

Window well seems to work OK for some

Two maples packed in mulch in the garage

Lastly, I keep some of the less hardy trees like my Japanese maples in an unheated garage that is attached to the house.  Putting the bonsai into a plastic milk crates or shallow boxes and then packing some mulch around each pot is a way to help them stay moist and well protected. In the photo, two trees are fit into the crate by stacking them.  I set the larger one first into the crate with a layer of mulch packed around the pot and then stacked the smaller onto it, and finishing with a second layer of mulch.

Also, since they are in the garage, keep in mind that dormant trees will still use a little water. Be sure to check these trees occasionally. Watering them is necessary.  Be especially vigilant if your trees are in very shallow pots.  I lost two prized maples a few winters ago that happened to be in shallow pots, and were watered the same as those in deeper ones.  But at some point the moister wasn't adequate and trees had dried out. It was painful to loose two incredible maples. So keep a close eye  on them.

Hopefully, your trees will emerge healthy and ready for the new season with a nice flush of enlightening bright green foliage.  After, all "If winter comes can spring be far behind?"