Ephemerals
Every spring, after a winter of normal rainfall, parts of the southwestern deserts are carpeted with a lush blanket of fast-growing annual herbs and wildflowers—the early spring ephemerals. The monument does not get massive displays, however, since it is lacking in the species that make the best show. But it does have many annuals that are beautiful individually or in small groups. Many of these “quickies” do not have the characteristics of desert plants; some of them, in fact, are part of the common vegetation of other climes where moisture is plentiful and summer temperatures are much less severe.
What are these “foreign” plants doing in the desert, and how do they survive? With its often frostfree winter climate and its normal December-to-March rains, the desert presents in early spring ideal growing weather for annuals that are able to compress a generation into several months. Several hundred species of plants have taken advantage of this situation.
There is WILD CARROT, which is a summer plant in South Carolina and a winter annual in California (where it is called “rattlesnake weed”). In the desert, its seeds lie dormant in the soil through the long, hot summer and the drying weather of autumn. Then, under the influence of winter rains and the soil-warming effects of early spring sunshine, they burst into rapid growth. One of a host of species, this early spring ephemeral is enabled by these favorable conditions to flower and mature its seed before the pall of summer heat and drought descends upon the desert. With their task complete, the parents wither and die. Their ripened seeds are scattered over the desert until winter rains enable them to cover the desert with another multicolored but short-lived carpet of foliage and bloom.
The one-season ephemerals do not limit themselves to the winter growing period. From July to September, local thundershowers deluge parts of the desert while other areas, not so fortunate, remain dry. Where rain has fallen, another and entirely different group of plants, called the summer ephemerals, find ideal conditions for growth and take their turn at weaving a desert carpet. Their seeds have lain dormant over winter. These summer “quickies” are plants that, farther south in Baja California and Sonora, Mexico, flourish during the winter rainy season. Saguaro National Monument is doubly fortunate in that it lies within a section of desert having not only its own year-round vegetation, but also summer wildflowers “borrowed,” for winter use, from its eastern and western neighbors, and winter wildflowers for summer decorations from its southern neighbors.
Phacelia, an ephemeral.
The short-lived leafy plants of summer and winter are able to compress their entire active life into 6 to 12 weeks when conditions are most suitable. Thus, they can escape all the rigorous periods of the desert climate by living for 8 or 9 months in the dormant seed stage. Some of the spectacular and colorful flowers of the monument are among these ephemerals that survive desert conditions by escaping them. It must be remembered, however, that when drought conditions or abnormally cold spring weather upset the norm—a not unusual occurrence—response of ephemeral plants is greatly restricted. If suitable conditions do not develop during the season for growth of a particular kind of ephemeral, its seeds will simply wait a year or more until conditions are favorable.
White tackstem.