Increasing winter chilling in the desert Southwest, 2013-14
Thought I might relay my experience at gaining adequate winter chilling in a greenhouse in Alpine, Texas. Winters average about 60/30F day/night temperatures with 75% sunshine.
My plan has been shade over the plants, heat at night, and use evaporative cooling by day. The objective being to maximize Utah chill hrs. That model predicts optimum chilling at 41F, none below 32F or above 59F, and negative chilling above 64F. So Alpine suffers in chilling by being too cold at night and too warm by day.
For 2013-14, I heated to 39-41F, on cold nights the heater comes on at 39 and off at 41. Cooling started stage one at 43F and evaporative cooling at 47F.
For the period Nov 22 thru Jan 30, 69 days, Utah hrs in the greenhouse were 1270, 77% of the total of 1656 hrs. Outside the same period experienced 350 Utah hrs and 751 hrs below 45F.
There are many ways this could be adapted outside a greenhouse. My first year here I used evaporative cooling in winter on potted trees setting in an unheated garage. This was mostly to delay bloom but could be used to increase chilling.
Another setup could be just shade cloth or shade with misting.
This post was edited by fruitnut on Sat, Feb 1, 14 at 15:29