New Coldframe
Small cold frame
Last year I built a small, energy efficient greenhouse to store many of our tropical plants in, as well as a place to place newly dug bamboo during cold dry periods during the winter. Mickey and I didn’t like the looks of the greenhouse after it was completed, it just sort ugly so I promised to take it down at the end of winter. I thought we would just mulch the tropicals heavily as we’ve done in the past but I really wanted to protect some of the really big elephant ears and banana trees. In the past I’ve waited until right before the first frost, cut off all the foilage, potted them up and placed in a cool greenhouse. I’ll do the same this year but it will be a small cold frame, 6′ by 12′ and about 3′ tall at the peak.
The cold frame is built into the ground.
This is where last years greenhouse was located. This part of the plant holding area is terraced, dropping down 2 feet. I built the walls from 4 x 4 timbers and 2 x 6 lumber. The back wall is the north side and it has dirt piled up behind it. This means the north and west walls are set 2 feet into the ground. When I built the walls I placed foam insulation behind those two walls help the greenhouse retain heat. I made a simple frame of 2 x 4 lumber for the south and east walls. I put foil lined, foam insulation on the inside of the frame. Two layers of 3/4 inch insulation with seams taped. I placed one layer on the inside of the north and west walls to further insulate them. The foam insulation, as well as the framing lumber were all salvaged from the greenhouse.
The roof on the cold frame opens.
The top of the cold frame was constructed from 2 x 2 lumber. I ripped the 2 x 4 boards on a table saw and screwed them together with deck screws. I have the plastic to cover the frame but will wait until closer to our first frost. I think I will cover the triangular ends with foam insulation. I made the pitch different on the south and north sides of the peak. This makes the south facing part to be larger. It is simple to open by raising up the edge and putting a prop under it. I hope that the reflective foil walls will help distribute what sunlight it does get. I will try to use a couple of incandescent lights to keep the temperature above freezing. Once the frame is filled with containers I’ll put in some leaves to help fill in and insulate the pots. I only need room for about 40 containers so with 72 square feet of space I should have close to half of the cold frame space available. I can use this as a short term storage for newly dug bamboo plants.
UPDATE
With our first frost due any time now we potted up about 50 elephant ears, gingers, and banana trees and placed them in the cold frame. I cut off the leaves, leaving a few inches of stalk I cut off the leaves, leaving a few inches of stalk.
Plants ready for winter
The north side of the cold frame is below ground level. I placed another layer of foam insulation against this wall and placed enough fill dirt to bring the level up as high as possible. I had some small elephant ears left from last year that never got planted so I buried them in the fill dirt, maybe they will sprout in the spring. I buried the edge of the plastic that draped down over the seam between the top and side to help seal it against cold air.
Front of cold frame (south side)
The cold frame is closed and well sealed. Notice the grove of bamboo behind it. This is P. vivax aureocaulis, often called Green Stripe Vivax bamboo.
Tags: clumpers, greenhouse, tropical
