One of our loveliest Arizona spring wildflowers is the graceful and delicate Doubting Mariposa Lily (Calochortus ambiguus), probably the most common and widespread Calochortus species found here.

Doubting Mariposa Lilies are found in grassy upland areas between 3600 and 8000 feet (1100 to 2438 m) in elevation. These native perennials can grow to up 2 feet (61 cm) tall, but most that I see are only about 1 foot (30 cm) tall.

The flowers are 2 inches (5 cm) or more in diameter, and since the flowers are atop tall, slender stems and many of the linear, grasslike leaves wither before flowering, the large flowers can almost look like they are floating in mid-air. Mariposa is Spanish for "butterfly", and the breeze touching a field of blooming Doubting Mariposa Lilies can magically transform them into what looks like a cloud of fluttering butterflies.

The flowers of Doubting Mariposa Lilies are quite variable, both in petal color and petal marking. Most Doubting Mariposa Lilies have white petals, but some can have grayish, violet, or pink petals. The petals often have a dark purple base and/or a dark purple median blotch, however some Doubting Mariposa Lily flowers lack these dark purple petal markings, and I have found marked and unmarked Doubting Mariposa Lilies growing side by side.

Doubting Mariposa Lilies can be a bit tricky to identify because there are four Calochortus species with similarly-colored flowers found here in Arizona. I identified these as C. ambiguus because of their upright, well-branched stems, mostly crescent-shaped, depressed petal glands, dark anthers, and lack of extremely hairy petal bands. Here are the key characteristics of these similar Calochortus species:

• Doubting Mariposa Lily (Calochortus ambiguus) – Upright, branched stems, round or crescent-shaped, depressed petal glands, flowers with dark anthers.
• Winding Mariposa Lily (Calochortus flexuosus) – Twining or trailing, branched stems, crescent-shaped, non-depressed petal glands, petals with a broad band of yellow at their base, usually no median purple blotch or just a faint one on the petals.
• Gunnison's Mariposa Lily (Calochortus gunnisonii) – Upright, unbranched stems, transversely oblong, non-depressed petal glands, petals with a broad, dense band of yellow hairs (often below a maroon line).
• Sego Lily (Calochortus nuttallii) – Upright, mostly unbranched stems, round, depressed petal glands, yellow or light pink anthers, a broad area of yellow at the base of the petals, often (but not always) a conspicuous purple median blotch.