Penny Wagner Desert annuals, like wildflowers, are adapted to the arid environment in many different ways. These include thick, waxy coverings on leaves and stems that reduce exposure and thus evaporation loss while the plant transpires or "breathes"; small leaves that 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 Montezuma Castle 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, datura, sand verbena, and yucca. |
NPS Photo / Nicholas Goodman Sacred Datura (Datura wrightii)Also known as thornapple, devil's trumpet, jimsonweed, or moonflower. This plant produces large, white flowers from spring through fall that measure more than five inches across and at least seven inches long. The flowers do not bloom until around sunset and each flower only lasts one day. Hawkmoths pollinate the flowers at night. The fruits are round, green, and covered with spikes. 
NPS Photo / Nicholas Goodman Silverleaf Nightshade (Solanum elaeagnifolium)Also known as silver horsenettle, bullnettle, or desert nightshade, silverleaf nightshade is best left untouched. The stems of the plant are covered in tiny, nettle-like hairs that cause skin irritation. During late summer and fall, the plant produces small, yellow or black fruits that resemble tomatoes and are poisonous if eaten. This particular plant produces a protein digesting enzyme which can be used in cheese making. Some Native Americans used crushed fruits to curdle milk.In some parts of the country it is considered invasive because of its hardiness and ability to outcompete other plants, even in Arizona. Natural resources staff have been working to remove it from the Pasture Trail at Montezuma Well. There is some debate over whether silverleaf nightshade originated in North or South America. 
NPS Photo / Nicholas Goodman Sunflowers (Helianthus annuus)Sunflowers grow in large numbers along the Pasture Trail at Montezuma Well and along roadways across the southwest during the summer. Native Americans such as the Hopi cultivated different varieties and used the seeds for food or dye. Although sunflowers remain a garden favorite, wild sunflowers and varieties cultivated in the southwest are more heat and sun resistant than others.
Photo by Sue Carnahan Parry's Penstemon (Penstemon parryi)Often found along trails and roadsides, this plant does not lose its leaves in the winter and displays bright pink, trumpet-shaped flowers in the spring. This is one of two similar looking species of penstemon that are found across the Verde Valley in the spring. The other, desert penstemon, blooms into summer while Parry's penstemon only blooms in the spring. With a few exceptions, this species is mostly found in Arizona and northern Sonora.
NPS Photo / Alice Wondrak Biel Globemallow (Sphaeralcea spp.)Four species of globemallow are found at Montezuma Castle and Montezuma Well. These plants are common along roadsides and disturbed areas and are often overlooked. Globemallows are extremely tolerant of heat and sun. Although most globemallow flowers appear during the spring and summer, flowers can be present at almost any time of the year. Because of this, they are usually a reliable source of nectar for bees and other pollinators. |
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Last updated: September 14, 2025