Wintering Plants in Pots - Part 2
Last week, I told you some of the ways that I protect hardy potted plants in my USDA zone 7 garden by digging them in or wrapping the pots. While these are probably the easiest ways to deal with larger pots, they don't work as well for plants in smaller than a nursery gallon sized pot. Smaller plants can tend to get smothered by leaves or washed out by hard rains if left exposed to the elements.
Frame It!
Cold frames, of some sort, are an indispensable part of gardening once you get into propagation of any description. You can buy them read-made or you can make your own. If you know you want a permanent frame, it's a good idea to build it of sturdy, rot-resistant materials and spend the money for an automatic vent opener. The solar variety will work fine for a frame if your lid isn't too heavy. Ventilation is of prime importance, since plants in a cold frame can cook quickly on a sunny day, even if the outside temperatures are well below freezing. I don't know about you, but I can think of a lot of things I need to do other than run outside every hour to check a cold frame!
Portable, Temporary or Permanent?
This sketch represents a typical cold frame. It can be portable or permanent. It can be just about any size you wish, although the best proportion will allow you to easily reach the back of the frame from the front while in a kneeling position. Your lid will need a support from front to back of the frame bottom every three feet (1m) on center - any farther apart and you'll find the lid will tend to sag over time. You can make a prop by notching a 2 x 4 so it sits on the bottom frame and has steps at intervals to allow the frame to be cracked or opened wider.
Portable frames are versatile because you can move them around, but their disadvantage is a lack of height to accommodate taller plants. Two feet deep on the high side isn't too much for many plants and that would make a frame that was pretty heavy to lug around. But, for smaller pots, they work quite well.
If you want this type of frame to be a permanent feature, you can build the sides and back taller or you can dig a hole the size of your frame (plus a bit for working room) and eighteen inches (.5m) deep; line the sides with concrete blocks - this dimension should allow for two 8 x 8 x 16 standard concrete blocks. Mortaring them together is best, but you can also drive stakes through the holes in the block, into the ground, to keep them in place and fill them with tamped earth. Use twelve inch (30.48cm) nominal height boards for the back of your frame. Put at least six inches (15.24cm) of sand in the bottom and you will end up with a frame that will take a two foot plant - anything larger than that is a candidate for digging or wrapping, not framing. The advantage in burying the block walls is the earth's insulation value. Unless you're in an extremely cold climate, the bottom of this depth frame should be well below frost level. I must admit working in it can be a bit awkward. I usually end up getting into mine to set and remove plants; a delicate business, to be sure. Otherwise, you're practically standing on your head as you lean over to reach the pots in the back row.
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