There is an increasing use of high stature plastic tunnels (macro-tunnels) to grow high value crops, such as raspberries, blueberries, vegetables and flowers. This is even in relatively frost free environment, such as coastal California. More commonly tunnels are used in colder climates to produce early season crops.  But along the California coast there is increasing use because of other benefits, such as improved production and reduced disease. There is estimated to be about 11,000 acres in tunnels in Santa Barbara County and even more in Ventura.

A recent, unpublished study by Mike Cahn et al with UCCE in Monterey County evaluated water use by raspberries in tunnels. They found that pan evaporation was reduced by 18% in the tunnels over the season compared to open-field grown raspberries.  Also, less water was applied for the inside trial than the adjacent outside trial.  Even with the reduction in applied water the soil moisture remained higher inside the tunnels than outside.     The canopy was larger earlier inside the tunnel than outside even though there evapotranspiration was lower inside the tunnels. The main components of transpiration are altered in tunnels. There is less radiation because of the interference of the plastic, less wind, higher humidity, despite the warmer temperatures.  

 toGrowing blueberries in a pot is not such a whacky idea.  Along the coast, they never get as big as the Central Valley or other places where they are grown. That's because they are in almost continuous flower and fruit production.  So when they are small, the pots can be put more closely together, reducing water use and weeds.  As the plants grow, the spacing can be increased.  Also, blueberries are very sensitive to high soil pH which is easier to correct with artificial substrates.  They are also prone to Phytophthora root rot, the pesticide for which can't be used by organic growers, but can be controlled by careful irrigation of a pot.  So the easier control of weeds and the easier control of root rot would be worth it to an organic grower, even though the initial expenses are higher.  Better control typically lead to higher yields.  Being able to control plant spacing might also make them less prone to frost damage because they could more easily be covered up when frost is forecast.