Almonds have been grown in California for hundreds of years, since the Spanish missionaries arrived here in the 1600s.  And walnuts are actually native to the state, Black Walnuts, that is.  Spanish settlers figured out long ago that you could graft so-called English walnuts onto the roots of the existing black walnut trees to get a nut that was much easier to crack.
Pistachios, on the other hand, are a very recent arrival to California.  Most of the world’s pistachios came from Iran until farmers here started planting them in the 1970s and 80s.
Almonds are a difficult crop to grow organically in Northern California.  They flower very early in the spring, and require pollination by bees to get a good crop.  Rain during the bloom causes diseases and prevents bees from flying.  Historically, the area where we farm is very wet during February and March, and almond yields are much lower than they are further south in the valley where it rains less.  Organic almond orchards have even lower yields.
Until recently there have been few orchards in our area, and we have not felt like planting our own orchard would be a good decision.  If the last two years are indicative of the future climate for our area, however, almonds may end up being a much more reliable crop.
Pistachios don’t like rain much either.  Wet weather creates ideal conditions for a blight that rots the nuts during and after bloom.  Unlike almonds, however, pistachios bloom much later in the spring — sometimes as late as the end of April.  That makes them a better choice for growing in our area, although in very wet years we have seen the disease take most of the crop.
Despite the dry weather last year during pistachio bloom, most of the state had a poor crop.  Pistachio pollination requires both male and female trees — the male trees do not bear nuts — and both genders must be flowering at the same time.  Last year, for reasons that are still not completely understood, there was very little overlap.  Researchers have speculated that extreme cold in December followed by the warm January threw the trees off somehow.
Walnuts are the most widely grown nut in the area around Winters.  Because they are big trees, they require much more water than either almonds or pistachios, and so actually benefit from the wetter winters in our area.  While they don’t like rain when they are blooming — very few non-tropical plants do really — they tend to flower later in the spring.
In the end, the extremely dry year led to a reduced crop of walnuts in 2014 due to smaller nut kernels as the trees had less soil moisture available to them.
We’re on our second round of nuts in your CSA boxes for 2015, and there will likely be a third and fourth.  That’s because we rely on the pistachios and walnuts in late winter when our fruit and vegetable availabilities are at their low point for the year.