When it comes to spring wildflowers in the Sonoran desert, timing is everything. There is a common misconception that if we get plenty of rain in the spring, wildflowers will abound. But truly eye-popping displays of desert annuals require a steady dose of winter rains beginning in November and lasting through February in order to germinate and grow a healthy crop of seedlings that will eventually flower. Lots of other factors come into play, but the records show that a cumulative rainfall of over four inches through the winter, preferably not in one giant storm, is the most reliable predictor for the abundance of spring wildflowers. This was the case for our most recent banner years, 2001 (7.07”), 2005 (7.72”) and 2008 (4.35”), when entire hillsides glowed orange with poppies, blue with lupines and valleys blazed hot pink with purple owl clover.
A decent monsoon the previous summer will help, but is less important than a consistent series of winter rains that keep the soil moist. In fact, the same banner years listed above actually had below average (< 2”) monsoon rains the previous summer. Cooler temperatures also help keep the evaporation levels low and tender seedlings from frying in the hot sun. Even if you want wildflowers in your yard, you need to scatter the seed no later than early November and then water them weekly for the next three months if you want to see some action.
So what’s the forecast for this year’s desert wildflowers? I'd say mild to moderately stunning. Records from the National Oceanic and Atmospheric Administration (NOAA) show that while the 2012 monsoon season was slightly above the 100+ year average of 2.71 inches, we’ve had a relatively dry winter. The gentle rains in early December and late January only generated a cumulative rainfall of about 2.30 inches for the Phoenix region. More rain in February and March can help, but it’s usually too little, too late. However, we should always be grateful for any amount of rain in the desert!
The good news is that there are always wildflowers somewhere; you just have to know where to look and plug into the wildflower watch networks to learn where the weekly hot spots are. Because rainfall varies a lot across the region, certain hills may be lusher than others, even compared to somewhere only a few miles away. Even a scant quarter inch of rain can make a big difference. In a dry year, north-facing hillsides are good places to scope out, since moisture will hang around a little longer on the shady sides of the hills. Even the north sides of large boulders and the shade of large trees will often be havens for annual wildflowers.
Although annuals may be sparse this year, many shrubs, perennials and cacti will bloom profusely, since they don’t have to start from seed. This is a great year for desert hyacinth (Dichelostemma capitatum), a delicate perennial plant that harbors a bulb deep below the soil surface. Thousands of slender succulent stems pierced the stony soils in desert hills throughout the region by early February, and will show off lavender blooms by early March. Bright orange globe mallows are another abundant hearty perennial commonly seen along roadsides throughout the desert. Flowering shrubs like brittlebush, wolfberry and ratany will always find energy to bloom, even if there is next to no rainfall.
In the Happy Valley region, you’re likely to find some brilliant patches of wildflowers in the Sonoran Preserve, east of Highway 17, just north of Jomax. Cave Creek Recreation Area north of Carefree Highway at 32nd Street and the Pipeline Trail at Lake Pleasant are also historically floriferous. Wherever you go, be sure to appreciate the miracle of each and every blossom.