• Double O Arch

    Arches

    National Park Utah

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Wildflowers

Stemless woollybase (Hymenoxys acaulis)
Stemless woollybase (Hymenoxys acaulis)
NPS Photo by Tom Gray
 

Desert annuals like grasses and wildflowers are adapted to the arid environment in many different ways. These include thick, waxy coverings on leaves and stems which reduce exposure and thus evaporative water loss; small leaves which reduce water loss while the plant transpires or “breathes” and receive less solar radiation; and deep taproots to reach further into the soil or shallow widespread roots that absorb surface water quickly.

Despite these adaptations, most desert wildflowers avoid drought and heat by surviving as seeds or bulbs stored in the soil, sometimes for decades. These seeds will only germinate after significant seasonal rainfall, so wildflower growth in Arches is highly variable year to year. April and May are generally the best months to see wildflowers, then again in early fall if there are a lot of summer monsoons.

Some desert plants take advantage of the nights’ cooler temperatures to flower. These evening-blooming plants include evening primrose, sacred datura, sand verbena and yucca. The yucca and the yucca moth have a fascinating nighttime association. After mating, the female moth gathers pollen from one yucca flower, packs it into a ball, and then flies into the night, locating other yucca flowers primarily by “smelling” with her antenna. She visits several flowers, each time laying some eggs in the base of the pistil and packing some of the pollen from her pollen ball down the pistil for her young to feed on. Thus she fertilizes the yucca flowers. Yucca flowers are only pollinated by yucca moths, and yucca moth young only feed on yucca pollen.

Did You Know?

Pinyon Pine

Pinyon trees do not produce pine nuts every year. These delicious nuts can only be harvested every three to seven years. This irregular schedule prevents animals from adapting to an abundance of pine nuts and guarantees that at least some nuts will become new trees instead of a quick meal.