Turritis glabra (Tower Mustard)

Plant Info
Also known as: Tower Rockcress
Genus:Turritis
Family:Brassicaceae (Mustard)
Life cycle:biennial, short-lived perennial
Origin:native
Habitat:part shade, sun; dry fields, roadsides, woodland edges
Bloom season:May - July
Plant height:1 to 5 feet
Wetland Indicator Status:none
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 4-petals Cluster type: flat Cluster type: raceme

[photo of flowers] An elongating raceme, with blooming flowers in a small flat, compact cluster at the top of the stem. Flowers are 1/8 to ¼ inch long with 4 white or creamy colored petals, 4 green to yellowish sepals darker on the tip end, several yellow stamens, and a flower stalk up to ½ inch long. The petals may be spreading but they're often seen only poking out of the sepals by a little bit and not fully open. A plant typically has multiple flowering branches.

Leaves and stem: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of stem leaves] Stem leaves are up to 3 inches long and 1 inch wide, generally lance-like, toothless, mostly hairless except perhaps around the edges, with a pointed tip and a pair of lobes at the base that wrap around and clasp the stem. Leaves become progressively smaller as they ascend the stem, and are covered with a waxy powder that gives them a blue-green cast.

[photo of basal leaves] Basal leaves are more spatula shaped with a blunt tip and shallow lobes or largish irregular teeth, hairy to varying degrees, especially on the underside along the midrib and along the edges. The stem is mostly smooth and light green, often also with a bluish cast.

Fruit: Fruit type: capsule/pod

[photo of fruit] Fruit is a straight slender pod up to 2½ inches long, containing 2 rows of tiny seeds. Pods are erect, crowded and hug the stem.

Notes:

Tower Mustard is more commonly known as Arabis glabra, but recent DNA testing has moved it to genus Turritis. It is not likely to be mistaken for any other species, easily identified by the clasping leaves and erect pods close to the stem. Most references put its maximum height at about 3½ feet, but I've seen late season plants close to 5 feet tall.

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More photos

Photos taken at Wild River State Park, Chisago county.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Marie - Wilson, WI (about an hour from St. Paul, MN)
on: 2016-05-28 11:04:43

I found this in my field this year for the first time. It was quite a challenge to identify it! An interesting note is that the upper leaves can sometimes be a striking deep purple color. According to illinoiswildflowers.info, this happens in cool spring weather when the plant is in full sun. I wonder if I only noticed the plant this year because the conditions were right for the purple color, making it stand out more. Thanks for the information!

Posted by: Donna G - Apple Valley raingarden
on: 2017-06-15 18:26:26

Found this year in my front yard rain garden which was established in 2007. University of MN identified it for us.

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