Building a Cold Frame

Around this time of year, every year the subject of what to do with our prized possessions during the winter surfaces. As in every year, we go about explaining how it is done. Several methods are used, probably the method of choice if one has the space is to build a cold frame.


For some unknown reason, after extensive research I have come to find out that a cold frame should measure 6 x 3 x 3 feet deep. They don't explain why but do say if more space is needed, then build a second one. The object of this article is not to discuss the validity of found arguments, but rather how to build a cold frame. The hole was dug out to a depth of 1 1/2 feet, 4 inches of 3/8 - 1/2" gravel was placed in the bottom of the hole and, then the pre-assembled box was lowered into the hole.

The entire cold frame is built with "below grade" pressure treated lumber. The frame is made of 2x4s whilst the siding is 5/4 1x6". The box was entirely assembled on the ground near the hole, as once assembled it is fairly heavy.


The entire box was insulated with 1 1/2" Styrofoam cut to size to fit between uprights.


1/4 inch galvanized mesh was added to the interior, to prevent rodents from entry into the cold frame. With the (insulated frame) upside down, wire mesh was added to the bottom, overlapping the exterior by 2 inches and stapled into place. Once the bottom completed, the cold frame was once again turned right side up and the walls where then screened (notice the overlapping conducted at the corners).


As seen the trees are mulched in to the first branch of every tree.

How to lay your trees in the cold frame
Prior to laying your trees to rest for their winter slumber, it is important to water each and every tree.

A layer of mulch is added to the bottom (an inch or so). Then the trees are added with the tallest ones towards the rear etc... the trees are mulched in pots and all up to their first branch. Then the mulch is given a good soaking. A piece of landscaping fabric is added to the inside of the cover. This I found out was important during my first winter as several trees woke up from their slumber rather early. e.g. early to mid February. In subsequent years with the cloth added my trees are waking up end February to mid March.

Winter maintenance
Do you drink when your sleeping? Neither will your trees or minimally at best. What I do when we get snow, I periodically fill the cold frame with snow, just like mother nature would and the trees are happy. As long as the mulch appears damp, your trees are fine. You can check the soil bu removing mulch and although the surface of the mulch might be dry, under the top layer the mulch and soil are quite damp, all is fine.

When spring come along watering the trees becomes paramount. The sign that the trees are ready to drink once again is when they start to bud. At this stage I remove the top layer of mulch and water my trees as required. This is also the time to remove the landscaping fabric from the lid and to leave the cold frame lid cracked a inch or so.

Note: For sake of clarity, the cold frame bottom is made out of galvanized mesh only.