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NATURAL HISTORY

MUNZ’S ONION } Allium munzii
FAMILY: Liliaceae

DESCRIPTION: Munz’s onion is a perennial herb and grows to six to 14 inches in height. It spends most of the year underground as a bulb; the bulbs themselves have a distinctive onion-like odor and taste. During flowering season, the plant bears a single hollow, cylindrical leaf, which can be up to one and a half times as long as the scape, or stem. When it blooms, the umbrella-shaped clusters of 10 to 35 small flowers can be white or red, depending on the plant’s age. Later in the blooming season, the plant bears a three-lobed fruit that houses many small, black seeds. Due to the fact that it dies back down to a stem for a certain portion of the year, the plant can only be detected when it blooms in April and May.

HABITAT: Munz’s onion prefers very thick, mesic clay soils at an altitude of 400 to 900 meters. It is usually found in open grasslands, coastal scrub, and juniper woodlands.

RANGE: This rare plant grows only in the western part of Riverside County, California.

LIFE CYCLE: Like many members of the lily family, Munz’s onion germinates from an underground, reddish-brown bulb. The growth process is slow: each plant takes anywhere from three to five years to reach maturity. When the flowering season draws near, the plant extends a stalk above ground, complete with a single, tube-shaped, hollow leaf. Munz’s onion blooms in April and May with a spray of small, milky-white flowers. As the season continues, the plant’s flowers change color: a red vein appears in the middle of each flower before the flowers all turn completely pinkish. Ever adaptable, Munz’s onion will change its breeding pattern to suit its environment — if there is not enough rainfall in a given year, many plants will not flower. Like some other members of the lily family, once the plant has bloomed it dies back to the bulb and remains dormant underground for the rest of the year. The plants will venture aboveground only in the spring of the coming year if adequate water is available.

THREATS: In the past, much of the Munz’s onion habitat was destroyed by clay mining. Today, this plant is most threatened by increased urbanization, agricultural activities (disking), off-road vehicle use, trampling and overgrazing by livestock, weed control measures, competition with nonnative species, and some clay mining.

POPULATION TREND: When it published its final rule on critical habitat, the U.S. Fish and Wildlife Service listed 19 extant populations of Munz’s onion. The largest population clusters remain in Harford County Park, Alberhill, Elsinore Peak, Dawson Canyon, Estelle Mountain, and Bachelor Mountain. The remaining populations’ numbers are perilously low: while six of the extant populations contain over 2,000 individuals, most contain fewer than 1,000. Many of the current populations are located dangerously near developing areas.

Photo by Ileene Anderson