Overwintering bonsai - preparation

This year I’ve decided to cut back on the # of trees I store in a bonsai nursery greenhouse since the cost of winter storage has nearly doubled in the last two years. Will store select trees in my unheated garage (attached to our home) instead, and place fewer trees in the greenhouse. I live in northern Vermont. Temperatures inside my garage can drop to mid-high twenties during the coldest part of the winter…but typically remain in the mid-upper 30’s fahrenheit until early Spring.

Have metal racks with shelves to store the trees. About 9 years ago I began storing a few junipers, 2 cherries and a number of one year-old seedlings (black pine, maple, crabapple, apricot) that have since grown into pre-bonsai, in my garage with great success. Nearly all have come through the Vermont winters unblemished.

As noted above, I plan to store a few of my better quality trees in the garage this year. That would include a shimpaku juniper, two needle junipers, a lovely crabapple, a larch and possibly one or two azaleas.

I’m comfortable with the idea, knowing that the more sensitive trees in my collection (redwood, quince, pomegranate, bald cypress) will be stored under ideal conditions that don’t vary. All trees headed for the garage will be cleaned of debris and moss etc. in the next two weeks.

I’d like to do a better job however, preparing the trees and am looking for advice on what insecticide spray or fungal spray to use before tucking them away for winter. Have previously used a combined product by Safer Brand and have not run into issues. With my more prized trees I’d like to be sure I’m following the best practices.

Would appreciate your thoughts or suggestions.

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I don’t have experience with harsh winters and tree care.

I do remember Ryan talking about fungicides though. In the Spring Fundementals video, at mark 1:50:30, he begins to talk about diseases and fungi that affect trees. He also makes some recommendations on what to use.

I would also recommend watching the Winter Preparation video for tips.