Thlaspi arvense (Field Pennycress)

Plant Info
Also known as:
Genus:Thlaspi
Family:Brassicaceae (Mustard)
Life cycle:annual
Origin:Europe
Status:
  • Weedy
Habitat:sun; roadsides, waste areas, fields, disturbed soil
Bloom season:April - June
Plant height:4 to 20 inches
Wetland Indicator Status:GP: FACU MW: FACU NCNE: UPL
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: round

[photo of flowers] Elongating clusters of stalked flowers at the top of the plant and at the tips of branching stems arising from the upper leaf axils, with a densely packed, rounded cluster of open flowers at the tip and fruit forming below. Upper branches are often initially horizontal, becoming ascending. Individual flowers are white, about ¼ inch across, with 4 oval petals and 6 yellowish green stamens, 3 on each side of the flat ovary. The 4 green sepals behind the flower have whitish edges.

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

[photo of leaves] There is a rosette of spatula shaped basal leaves that wilt away early. Stem leaves are 1 to 4 inches long and up to 1 inch wide, hairless, with irregular blunt teeth and a rounded or blunt point at the tip. The edges are often a little wavy. Leaves near the base of the plant may have short stems; those nearer the top are more clasping. Attachment is alternate. Stems are ribbed, hairless, and branched in the upper plant.

Fruit: Fruit type: capsule/pod

[photo of fruit] Fruit is a flat oval pod about ½ inch long with a notch at the tip. It dries to a papery brown shell. Each side of the pod holds up to 8 seeds.

Notes:

The flowers of Field Pennycress are not very distinctive, but the seedpods are and make this plant easy to identify.

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More photos

Photos by K. Chayka taken in Ramsey County. Other photos courtesy Peter M. Dziuk.

Comments

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

Posted by: Crista S - North Mankato
on: 2016-04-30 11:00:16

I have this growing in one of my small gardens. The way it came up was like it was specifically planted there. I let it grow because it kind of looked like the annual I planted last year. Do I leave it grow or pull it out?

Posted by: K. Chayka
on: 2016-04-30 12:34:59

Crista, it's a weed, though not a terribly aggressive one. I don't think it has much value to wildlife and I don't personally find it that attractive, though the seed heads are kind of interesting. Use your best judgement.

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