Editor's note: This article was originally printed in the February 2010 issue of the Newsletter for Members.
Spring wildflowers are notoriously localized and hard to quantify. Wildflower seasons are easier to describe, but both lend themselves to fanciful hyperbole, mainly because their emotional impact often overshadows the reality on the ground. There is morbid silence or low grumbling during poor wildflower years, but in great years, like 2001, it’s not unusual to hear a field botanist fawn over a hillside of Mexican goldpoppies with the same adjectives as a Grand Canyon visitor might use at his first look over the South Rim.
Emotional descriptors like “amazing” or “incredible” or even “mind-bending” don’t add up to much when appraising the last decade of wildflowers in the vicinity of Boyce Thompson Arboretum. For that, I had to sift through the detailed field notes that I’ve kept over the years, skip over the plethora of oohs and aahs, and try to drill down to the nitty gritty of what was actually observed.
But what sounds easy really defies scientific methods: wildflowers are impossible to count, difficult to measure, and there is generally no easy baseline to compare them year-to-year. So, anecdotal appraisals inevitably rule, with comments like the one that I wrote for Mexican goldpoppies in 2001: “Easily the best in 23 years.” Seven years later, I noted that the brittlebush display on the hillsides across from the entrance to the Arboretum was the best in 20 years.
Neither of these references to great seas of orange and yellow would do much to impress a twenty-year-old sophomore botany major who is too young to have his own historical context. I made a better attempt by writing that the west-facing slopes of hills near Silly Mountain “appeared to morph from an opaque dressing of poppy orange to clear, brittlebush yellow in mid-April of 2008”—at least this description infers that poppies bloom first, that they are orange-ish, and that they are eventually forced to hand over the reins to the more heat tolerant brittlebush.
Not every year is a great season, and 2002, 2003, and 2007 proved to be real stinkers. The years 2004 and 2006 were spotty and forgettable. 2009 was a little better, favoring yellow fiddlenecks, purple bladder pods, and a respectable smattering of the usual suspects, but it lacked the large masses of anything in particular. The years 2001, 2005, and 2008, however, are why we risk sunstroke, dehydration, and basal cell carcinomas and venture out into the desert.
The sweet spot for the timing of annual and herbaceous perennial flowers is generally mid-March to mid-April, but the ideal rain to generate these flowers is generally hoped for in October and November of the previous year, nudged along by rain every few weeks until spring. When looking at weather records for this decade on month-by-month basis, the Arboretum was blessed with copious amounts of rainfall in October and November of 2000 and 2007. Good rain in in the 2004-2005 season, however, was skewed more toward January and February.
The bottom line is that even though 2001, 2005, and 2008 all fall within the good-to-great category of wildflower shows, 2005 was different, favoring different wildflower species in different densities, sizes, and locations, while sharing some similarities with 2001 and 2008.
The envelope please…
The year 2001 was the season of the Mexican goldpoppy, with hillsides covered from Apache Junction to the Arboretum, and from Globe to Roosevelt Lake, with picture post card masses at the foot of the Superstition Mountains near Lost Dutchman State Park. Nearly every common wildflower on the desert menu was represented, not just in enormous combined masses, but with super-sized individual plants that feasted on the adequate—and well timed—moisture.
The 2005 season favored tremendous stands of brittlebush. Owl clover blanketed some hillsides in poppy-like numbers. Many individual plants of cheeseweed (Malva neglecta) were five feet tall and ten feet across. Scorpionweeds grew to a whopping four to five feet high in places and would have toppled over had they not been supported by surrounding jojobas and creosotes. It was also a good year for desert lupines, but with scant crowds of goldpoppies.
Wildflowers in 2008 were more like those of a subdued 2001, but with some exceptional standouts. Mexican goldpoppies covered many hillsides in the same areas as 2001, and brittlebush was more profuse and showy than any other time in the decade. Scorpionweed covered slopes above the Queen Creek tunnel and freakish sizes and numbers of desert hyacinths, aka blue dicks, were everywhere, some nearly three feet tall and mixed in cryptically with the similarly colored desert lupines. This was also a good year for the lesser known Gilia scopulorum.
The outcome of 2010 is still up for grabs. Less than two inches of rain fell during October, November, and December of 2009, then seven inches fell on the dry ground in the third week in January. As of mid-February, the desert floor is green, but it’s still too early to tell which wildflowers will rise (or fall) in the last spring wildflower stand of the decade.