Timing/Soil Temperatures for Full Repot of Japanese Maples
New poster and new to keeping trees in containers. I have been a lurker here for some time and have tried to do my due diligence.
My goal is to keep some (narrowed list down to 10 that I absolutely want, currently have 3 of those, list may grow as time goes along) Japanese Maples in containers long term. Through root pruning, size of container, pruning, partial defoliation, wiring, etc, I want to keep these trees semi dwarfed and shaped (however, I don't want full on bonsai, just small versions of what I've seen in Japanese gardens I've visited in the Puget Sound area).
I've choosen cedar containers that are approximately 7.5-8 gallons. I'm going to use the 1,1,1 gritty mix (currently have approximately 30 gallons screened and mixed up waiting on the right time).
Posts I've read regarding the process and timing or full repots indicate that the best time is during the quiescent period. I've also read that this period begins when the tree roots reach a certain number of thermal units, and that this can be estimated when the soil temperature is above 45 degrees. I've also read in my research about Japanese Maples in the Pacific Northwest, that Japanese Maples can have problems with root rot and fungus when roots are pruned too early, due to the cooler, wet spings we tend to have.
Air temperatures here have been in the mid 40's to mid 50's during the day, dropping to the upper 20's to low 30's at night. I used a meat thermometer (don't tell my wife) to try to measure the soil temperature in the 2 gallon nursery containers the three Japanese Maples are in and got an unexpected result. The soil temperature in the pots measured approximatley 50 degrees.
So now finally to my questions. 1) How accurate would using a meat thermometer be at measuring soil temperatures? 2) If the soil temperature I've measured today is reasonably accurate, should I go ahead and perform the full repot, or wait until either night time temps remain above freezing or until buds begin to noticably swell (The buds still look very small compaired to the buds we saw on some Japanese Maples in a garden in south Seattle/Tukwila yesterday.)?
Thanks in advance for any help given,