Solutions for Pot-in-Pot Root Escape, Root Circling, and Heat Shock at Harvest
Carl E. Whitcomb and Andy C. Whitcomb
Heat, cold, and blow-over have been major problems plaguing plant production in the unnatural environment of man-made containers. In their natural environment, roots are protected by the insulating effect of soil and surface debris. Sensitivity to temperature extremes by plant roots appears to vary only modestly among species. Developing the pot-in-pot system (P+P) by installing a "socket" pot in the ground and inserting a production pot inside — seemed the golden solution for insulating container rootballs from temperature extremes. However, in many locations, P+P has turned out to be more akin to iron pyrites.
The pot-in-pot system was first tried with high expectations starting in 1973 (Hogan et al., 1974). Most tree species grew well a clay loam or a sandy clay loam soil. However, after two growing seasons with extensive rain periods, initial P+P studies ended with many dead plants. So P+P was written off as a good idea that did not work. The concept next surfaced, when
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