Brassicaceae : Arabis glabra

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Family Name

Brassicaceae

Common Name

Tower mustard, tower rockcress

Description

Arabis glabra is a biennial herb growing from a stout taproot. The stem is erect usually unbranched toward the base and branching near the top, growing from 60 to 120 cm tall. The basal leaves are spatulate to oblanceolate, entire to dentate and 5-12 cm long by 1-3 cm wide. The cauline leaves are sessile, lanceolate, entire to denticulate and variable in size (2-10 cm by 1-3 cm) with smaller leaves toward the top. The small flowers are arrayed in racemes and greenish white to yellow in color. The 4 sepals are membranous 2-5 mm long, rounded to subacuminate. The petals are 2.5-6 mm long . the fruit is a cylindrical silique 5-10 cm long and 0.8-1.3 mm wide, with pedicels that are erect or appressed and 7-18 mm long at maturity. The seeds are in 1-2 rows and are about 1 mm long and 0.15 mm wide. Tower rockcress grows in dry prairies on ledges and the edges of woodlands, blooming in May and June. It is much more common in the western side of South Dakota.

Additional Notes

Tower mustard can be weedy and is seldom planted as an ornamental. The leaves of the first year’s growth are spicey and can be used in salads.

Horticulture Notes

Seed collection: Seed become mature in June to July when the siliques begin to dehisce.

Germination: Seeds are dormant and need 60 days cold treatment or can be planted out in the fall.

Light: Full sun.

Soils: Will grow in most soils but does best in well drained soils.

Water: can tolerate medium wet to dry conditions.

Note: As a biennial, it produces leave the first year and bolts and produces flowers in the second year.