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The various species of Boechera are almost always difficult to tell apart. Some experts believe that the genus needs an entirely new evaluation leading to a new key. I used a number of keys to identify the species shown in this web site and I am reasonably sure that the identifications are correct. Boecheras have a further problem: their genus name has been a subject of debate. For two centuries "Arabis", a name given by Linnaeus in 1753 to Old World species, was the accepted genus name for all the similar New World plants, including those shown in this web site. Genetic research by Löve and Löve led them to believe that the Old World genus and the New World genus were not the same and in 1978 they created the Boechera genus. In 1982 William Weber furthered their work and reassigned almost all New World Arabis species to the Boechera genus. Most botanists now accept Boechera for the New World members of what had previously been called Arabis. Boechera is the accepted name in Colorado Flora, Intermountain Flora, Flora of North America, The Synthesis, the USDA Plants Database, etc. But Stanley Welsh has this to say in his 4th edition of A Utah Flora:
Other botanists agree with what Welsh implies in his last statement: morphologically, the New World species are nearly identical to the Old World species. Further, as noted above, the New World species are very similar to each other. The authors of Intermountain Flora indicate, "The morphological similarities appear to be due to convergent evolution, a curse with which the Brassicaceae burdens us." To sum: most botanists believe that laboratory work indicates that the New World species are genetically distinct from the Old World species and that morphological, field characteristics should not take priority in naming the genus. Tyge Boecher was a 20th century Danish botanist who studied the flora of Greenland. Boechera is often pronounced "Boo-ker-uh", "Bow-ker-uh", Beck-er-uh", or "Betch-er-uh". (More biographical information). |
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Boechera holboellii. (Rockcress). Synonym: Arabis holboellii. Brassicaceae (Mustard Family) Semi-deserts, foothills. Woodlands,
shrublands, openings. Spring. Boechera holboellii can grow to over two feet tall with large (for this genus) flowers. It has a a cluster of basal leaves, short stem leaves that clasp the stem, and seed pods (siliques) that are up to three inches long and pendulant. As is true of many Boecheras, flower color ranges through blues and pinks to occasional whites. All the Boecheras shown on this page share similar Sagebrush and Pinyon/Juniper woodlands habitat. Carl Peter Holboll (1795-1856) collected this species in 1828 in Greenland. (More biographical information about Holboll.) |
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Boechera holboellii. (Rockcress). Synonym: Arabis holboellii. Semi-deserts, foothills. Woodlands,
shrublands, openings. Spring. Compare the basal leaves of this Boechera with those of the other Boecheras shown on this page. Notice the caudex, the woody stem. |
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Boechera holboellii. (Rockcress). Synonym: Arabis holboellii. Semi-deserts, foothills. Woodlands,
shrublands, openings. Spring. Branching hairs, especially on the basal leave, are characteristic of this species. |
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Boechera holboellii. (Rockcress). Synonym: Arabis holboellii. Semi-deserts, foothills. Woodlands,
shrublands, openings. Spring. Stem leaves usually clasp the stem, are overlap the leaf above them (i.e., are longer than the internode), roll inward, and are reduced in size upward. Fruit stems ("pedicels") and fruit ("siliques" -- very light green/white in the photo) typically droop, as shown here in the upper right of the photograph. |
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Boechera holboellii. (Rockcress). Synonym: Arabis holboellii. Semi-deserts, foothills. Woodlands,
shrublands, openings. Spring. |
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| Boechera perennans. (Rockcress). Synonym: Arabis perennans. Brassicaceae (Mustard Family) Semi-deserts, foothills. Woodlands,
shrublands, openings. Spring. This delicate Boechera grows to be about as tall as B. pulchra, but it has much smaller flowers. Flower color in both Boecheras ranges through blues and pinks to occasional whites. The two plants share similar Sagebrush and Pinyon/Juniper woodlands. The siliques (seed pods) of this Boechera are long, narrow, and project outward from the stem or arch downward. "Perennans" is from the Latin for "perennial". This plant was first collected in Arizona in 1881 and was named Arabis perennans by Sereno Watson in 1887. William Weber named it Boechera perennans in 1982. |
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Boechera perennans. (Rockcress). Synonym: Arabis perennans. Brassicaceae (Mustard Family) Semi-deserts, foothills. Woodlands,
shrublands, openings. Spring. Several characteristics of B. perennans shown in the photo at left help to set it apart from other Boecheras. The basal rosette sits atop a caudex (a persistent woody base of a herbaceous plant), the rosette is made up of many shallowly-toothed leaves, fine hairs cover the leaves and multiple stems, and the stem leaves are short, clasp the stem, and have a blue-green tint to them. |
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Boechera perennans. (Rockcress). Synonym: Arabis perennans. Brassicaceae (Mustard Family) Semi-deserts, foothills. Woodlands,
shrublands, openings. Spring. The long, slightly down-turning siliques can be seen in the background and to the left. |
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Arabis pulchra. (Rockcress). Synonym: Boechera pulchra. Brassicaceae (Mustard Family) Semi-desert, foothills. Woodlands, shrublands,
openings. Spring. This slender, dainty, and lovely (thus the Latin, "pulchra", meaning "beautiful") member of the Mustard Family grows in open, sunny, semi-desert areas of the Four Corners. The plant is easily passed by because it is so slender and its flowers are so pale, varying from nearly white to pink to lavender-purple. M. E. Jones named this plant Arabis pulchra in 1887 from a specimen he collected in Nevada in 1882, and William Weber renamed it Boechera pulchra in 1982. |
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Arabis pulchra. (Rockcress). Synonym: Boechera pulchra. Brassicaceae (Mustard Family) Semi-desert, foothills. Woodlands, shrublands,
openings. Spring. Stem and pedicels (flower and fruit stems) are hairy. Fruits (often called siliques in the Brassicaceae) are more and more pendant as they elongate. |
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Arabis pulchra. (Rockcress). Synonym: Boechera pulchra. Brassicaceae (Mustard Family) Semi-desert, foothills. Woodlands, shrublands,
openings. Spring. Narrow, pubescent leaves are in a loose basal array and are shorter than the stem leaves. Notice the branched caudex, the woody base of this otherwise herbaceous plant. Other species of Boechera can have tight clusters of basal leaves and no caudex. |
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Arabis pulchra. (Rockcress). Synonym: Boechera pulchra. Brassicaceae (Mustard Family) Semi-desert, foothills. Woodlands, shrublands,
openings. Spring. |
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Arabis pulchra. (Rockcress). Synonym: Boechera pulchra. Brassicaceae (Mustard Family) Semi-desert, foothills. Woodlands, shrublands,
openings. Spring. |
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Arabis pulchra. (Rockcress). Synonym: Boechera pulchra. Brassicaceae (Mustard Family) Semi-desert, foothills. Woodlands, shrublands,
openings. Spring. |
Range map © John Kartesz,
County Color Key
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Range map for Boechera holboellii
Range map for Boechera perennans
Range map for Arabis pulchra |