Bay area Tulipa

Nathan Lange
Thu, 11 Apr 2013 13:49:44 PDT

For people living in California, the University of California 
provides chilling accumulation models with data for many locations 
throughout California:…
This information is provided for fruit and nut growers but is very 
useful for growers of other species requiring vernalization and/or 
stratification.  Other universities likely provide similar 
information.  This data is mostly limited by the number of 
locations.  The amount of winter chilling varies greatly in the Bay 
Area between years and especially by location.  For example, If you 
look at the data for the "Oakland Foothills" which is the closest 
station in Alameda County most similar to the University of 
California Botanical Garden, there have only been about 450 to 900 
cumulative chilling hours per year since 2004.  However, if you live 
30 miles away in Pleasanton (further inland), there have been about 
800 to 1200 cumulative chilling hours per year since 2004.  With such 
huge annual chilling differences, successful flowering of many 
species requiring "more" vernalization will undoubtedly vary 
significantly from year to year in marginally cold locations like Berkeley.

 From a cumulative chilling perspective, this past winter has been 
one of the coldest in the Bay Area in years.  So far, I have seen 
this reflected in both earlier, more uniform flowering times for 
bulbs that generally require more vernalization (Tulips) and 
outstanding germination rates for species (Calochortus, Fritillaria) 
planted late.


At 08:11 AM 4/11/2013, you wrote:
>Being from St. Louis, I'm not sure that a species that grows in Missouri
>would have a chance in the Bay Area if cold is required.
>Paul Licht, Director
>University of California Botanical Garden
>200 Centennial Drive
>Berkeley, CA 94720

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