[Rockcresses: The Genus Arabis (and Boechera) East of the Cascade Mountains of Oregon and Washington]

Woodland Rockcress, Holboell's Rockcress

Boechera pinetorum

Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii

Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii)

Holboell's rockcress (variety pinetorum) as seen on rocky slopes along Trail #201 above Wildcat Basin, Strawberry Wilderness...........July 1, 2010. Note the curved pedicel with minute, stiff, forked hairs.


Stem leaves of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii)The photo at right shows the leaves of Holboell's rockcress (variety pinetorum) as seen at Indian Rock (to the northwest of La Grande, OR) in the Wallowa-Whitman NF...........July 3, 2001.

Characteristics:

Holboell's rockcress is a biennial or short-lived perennial wildflower. One to several simple (to branched above) stems arise to a height of 100 cm. The lower part of the plant is strongly haired with simple or radially branched hairs, while the herbage is smooth to uniformly hairy above. The basal leaves are typically arranged in a basal rosette of linear-oblanceolate to broad, oblanceolate-spatulate leaves which are 1-5.5 cm long and 2-7 mm wide. The blades range from entire to toothed and are typically covered with fine felt-like hairs or longer, coarse or fine hairs. The numerous stem leaves often overlap each other and are often petiolate, although the upper leaves on some varieties are clasping with heart-shaped bases. They range from lanceolate to narrowly oblanceolate in shape and 1-5 cm long and 2-7 mm wide. Their blades are typically pubescent although they may be glabrous on some varieties.

The inflorescence is a densely-flowered raceme of 20-100 white, pink or most commonly, pinkish-purple flowers. The pedicels are 5-15 mm long and either uniformly curved downwards or more commonly abruptly bent downwards at the base. The pedicels vary from glabrous to hairy. Each of the 4 sepals is glabrous to hairy and each is 2.5-5 mm long. Each of the 4 petals is 5-10 mm long. The fruits are glabrous siliques from 3-7 cm long and 1-2 mm wide.

Variety pinetorum has simple to branched stems above from 30-90 cm high. They have a looser, coarser herbage on the lower stems and they are nearly glabrous near the inflorescence. The pedicels are arched to gently recurved.


Varieties:

Variety collinsii: Stem leaves with heart-shaped bases that often clasp the stem. Petals less than 7 mm long. Pedicels bent sharply downwards at their base. The siliques are more or less straight. Found from Washington to Alberta, Wyoming and east through he Dakotas and Manitoba to Quebec.

Variety pendulocarpa: Stem leaves lack heart-shaped bases. Found from British Columbia south to California and east to Montana and Colorado.

Variety pinetorum: Stem leaves with heart-shaped bases that often clasp the stem. Basal leaves are coarsely hairy. Pedicels uniformly curved outwards and downwards, not sharply reflexed downwards at the base. The siliques are thus spreading-drooping with the tip often incurved. Found from British Columbia south to California and east to Saskatchewan and Colorado.

Variety retrofracta: Stem leaves with heart-shaped bases that often clasp the stem. Leaves with margins rolled under, the upper ones pubescent. The basal leaves are covered in short, dense, felt-like hairs. Pedicels bent sharply downwards at their base. Petals over 7 mm long. Siliques 1.5-2 mm wide and more or less straight. Found from the Yukon and British Columbia south to California and east to Alberta (and occasionally to Quebec) and Colorado.


Habitat:

Hairy rock cress is found in forests and forest openings at all elevations.


Range:

Hairy rock cress is found from the Arctic south through much of North America to California, Arizona, and New Mexico, and as far east as the mid-Atlantic states.


Close-up of a flower of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Developing fruits of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Close-up sideview of a flower of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii)

Dorsal view of a stem leaf of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Ventral leaf surface of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii)

Holboell's rockcress (variety pinetorum) as seen on rocky slopes along Trail #201 above Wildcat Basin, Strawberry Wilderness...........July 1, 2010. Note the curved pedicel with minute, stiff, forked hairs. Note the bases of the stem leaves which are auriculate but not clasping, the leaf margins which are not rolled under, the gently curved pedicels, and the forked hairs on the sepals.

Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Inflorescence of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii)

Flowers of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Flowers of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Inflorescence of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii)

What may be Holboell's rockcress (B. pinetorum) as seen in open forest near the south side of the summit of Kamiak Butte, Kamiak Butte County Park, Whitman County, Washington........April 29, 2013. I'd want to see the fruits to verify its identification.

Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii)

Holboell's rockcress (B. pinetorum) blooming on scablands along Trail #808A where slopes begin descending down southward towards Brush Creek atop Lookout Mt., Ochoco National Forest........May 29, 2016.

Stem leaves of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Basal and lower stem leaves of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Inflorescence of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii)

Fruit of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii)

Inflorescence of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Stem leaves of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Inflorescence of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii)

Holboell's rockcress (B. pinetorum) as seen along the Fremont National Recreation Trail #160 on the northwest slopes of Hager Mountain, Fremont National Forest.......May 19, 2016.

Spreading fruit of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii)

The photo above shows the fruit of Holboell's rockcress (variety pinetorum) as seen at Indian Rock (to the northwest of La Grande, OR) in the Wallowa-Whitman NF...........July 3, 2001. Note the spreading pedicel with minute, stiff hairs and the capsule which curves downward at the tip.

Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii)

Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii) - Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii)

A set of photos of woodland rockcress as seen at Jim or Chop Creek, North Fork Catherine Creek Trail #1905, Eagle Cap Wilderness......June 12, 2018.

Basal leaves of Woodland Rockcress, Holboell's Rockcress: Boechera pinetorum (Synonyms: Arabis holboellii, Arabis holboellii var. pinetorum, Boechera holboellii)
The photo above shows a close-up of the basal rosette of leaves of Holboell's rockcress (variety pinetorum) as seen at Indian Rock (to the northwest of La Grande, OR) in the Wallowa-Whitman NF...........July 3, 2001. Note the mostly entire, narrow leaves.

Paul Slichter