For many of us in the West, the season has gotten off to a slow start. Weather forecasters had been predicting a significant El Nino event this winter, but in most places out West we received only slightly more precipitation than normal. Due to myriad microclimatic effects, seasonal totals were, of course, highly variable across the region. Officially, the water year runs from October 1 through September 30, but in most years our Mediterranean climate pattern means that we will see no rain from early May until late September. NOAA maintains an incredible website for the West with rain year to date totals: http://www.cnrfc.noaa.gov/monthly_precip.php
Looking at this site, you can see quite a range of rainfall, from Long Beach at 15.65″ or 125% of normal, Reno at 7.29″ or 129% of normal, Tahoe at 28.65″ or 95% of normal, Death Valley at 3.27″ or 178% of normal, King City at 13.94″ or 117% of normal, Santa Cruz at 30.7″ or 103% of normal and at my home in the Santa Cruz mountains 50.9″ or 111% of normal. There were of course both wetter and drier places but on the whole, this winter was fairly normal and only slightly wetter than usual. In a place like Death Valley, where the splendor of the ephemeral Spring wildflowers is so dependent on precipitation, 178% of normal should bode well for a spectacular show of color, but the spring display is dependent on a combination of factors: both the timing and amount of rainfall, the temperature patterns in spring and on the presence or absence of strong, drying winds. This bloom season has been a good one in Death Valley, but with almost no rain in the beginning of the winter, the rains mostly concentrated in January and February, and a relatively quick rise in temperatures this Spring, it has not proven to be the outstanding display that 3.78″ could portend.
While it has not been an excessively wet year, closer to home, our rains continued with unsettling frequency and far later into spring, than many growers would like. In most years, we can typically count on a window of opportunity where we have appropriate soil moisture, somewhere in the range of 50-70% of field capacity, sometime between early March and early April. This allows for major soil operations: mowing, spading/discing, and pulling beds, when we can actually enhance soil quality rather than degrade and compact our most precious resource by working ground that is too wet. This season, however, we had between an half and one inch of rain every 5-8 days from mid February through mid May and temperatures have been abnormally cool.
Placing soil health as an utmost priority and truly desiring to avoid compaction and crusting, this has meant that many a vegetable and flower transplant has languished in the greenhouse hardening off area and that many direct sown species were as much as six weeks behind schedule when the seeds finally did make it in the ground.
Although we are fortunate not to have our growing season strictly bounded by hard frosts, each spring we gamble with the patterns of rainfall and dryness, hoping for enough precipitation to keep our cover crops and overwintered cash crops happy enough so we do not have to think about irrigation, but at the same time hoping that high pressure and the jet stream will take a favorable turn by early February, that warm temperatures and wind will draw moisture from our soils and that we will be able to cultivate and plant early. Sometimes, this is indeed what happens. Sometimes it is not at all the case. In Santa Cruz we only received 103% of normal, but because of the consistently late delivery of rain, we have started 2010 off remarkably slow. Were it not for perennials and bulb crops, most growers in our region would be in very dire straits. How thankful we all are for the iris, tulip, daffodil, crocosmia and other bulblike stalwarts from underground. And for the ever-reliable anigozanthus, alstroemeria, achillea, nepeta, phygelius, physocarpus and of course the rose.
Here’s hoping for a long and productive summer, with the consolation of knowing that we have had a good season of groundwater recharge.
UCSC Center for Agroecology
Christof Bernau UCSC Center for Agroecology Contact at [email protected]