Q.How To Protect My Rhodendrons From Winter Kill And Freeze If Planted In A Retaining Wall. In Minnesota.
Hi. I have 2 established Rhodendrons planted years ago in a retaining wall. They are not big but are not small either.Every year before it freezes here I cover the base of them packed thick with leafs. They have landscaping rocks over the soil. Every winter I have also been wrapping just the base of them ( over the leafs ) with a layer of burlap. With climate change and unpredictable weather we get snow and then have a 50 degree day now. I covered the whole plants leaf and branches instead of the bases recently because we got a sudden snow and drop in temperature. I generally watered them weekly because they are also under a large overhang and they get no rain.( Yes this was a dumb place to plant them but too late now ) I was not able water them at the normal last weekly time because we got a sudden below 32 degrees and an inch or more of snow. Now it’s been below 32 degrees at night and in the 40s during the day. I have 2 questions. Should I try to water them one more time with this iffy weather or will the roots get frozen and damaged? And, should I keep the burlap completely over them covering them for the winter instead of just wrapping the base and not worry about the branches and leafs freezing ? Thank you very any help !!
Certified GKH Gardening Expert
It sounds like you are doing what you need to be doing, though I would have opted for growing these in container in your zone. I would only cover during the coldest parts of the year. They can, easily, survive freezing temperatures. They cannot survive the lows in the middle of the winter without protection. Do not cover them until the weather stays below freezing.
I would expect the next several years to get, progressively, cooler as we get into the brunt of the sun's 30 year cycle deemed "The Grand Solar Minimum".
If you would like to obtain better long term forecasts, I would consult with solar cycle charts, as well as keeping up with solar wind and radiant temperature data. With these pieces of data, it is possible to predict, with decent accuracy, how harsh or mild a particular set of winters will be.