Narrowleaf bittercress (Cardamine impatiens)

Narrowleaf bittercress flowers and leaves.

 
 

Narrowleaf bittercress generally grows in forested areas, often near waterways, and has been observed outcompeting native vegetation. Narrowleaf bittercress is fairly new to Minnesota and its distribution and impacts are not thoroughly understood. Any potential sightings should be reported to the Minnesota Department of Agriculture.

Description

Appearance

When narrowleaf bittercress germinates it grows as a round grouping of leaves (rosette) near the ground. In most cases it stays as a rosette for the first year and then in its second year it sends up a flowering stalk, flowers, and dies. In some cases the first year plant sends up a flowering stalk. Flowering stalks can grow up to 2.5 feet tall and have small white flowers with four white petals or no petals visible.

Leaves and Stem

When narrowleaf bittercress germinates it grows as a round grouping of leaves (rosette) near the ground. The rosette leaves have 3-11 leaflets that are round with lobes. In most cases it stays as a rosette for the first year and then in its second year it sends up a flowering stalk, but in some cases the first year plant sends up a flowering stalk. The flowering stalks can grow up to 2.5 feet tall. Leaves are alternate (come off the stem one at time at each leaf node). Leaves have 6-20 leaflets that are more linear and less lobed than the rosette leaflets. At the point where the leaf attaches to the stem there are small green growths called "auricles" that grasp the stem and look like two small points extending away from the stem.

Flowers

Narrowleaf bittercress has small (0.1 inch across) flowers with four white petals although petals are often absent. Flowers grow in clusters. Plants flower from May through August.

Seeds

Narrowleaf bittercress produces long, slender seedpods that can reach 0.8 inches in length. Seedpods can produce multiple seeds.

Roots

Narrowleaf bittercress has a taproot.

Biology

When narrowleaf bittercress germinates it grows as a round grouping of leaves (rosette) near the ground. In most cases it acts as a biennial and stays as a rosette for the first year and then in its second year it sends up a flowering stalk, flowers, and dies. In some cases it acts as an annual and the first year plant sends up a flowering stalk. Narrowleaf bittercress is commonly found in forest understories and near waterways, but can occasionally be found in more open, sunny areas.

Origin and Spread

Narrowleaf bittercress is native to Europe and Asia and it is not clear how it was introduced to the United States. It was first found in the northeastern United States in 1916 and first confirmed in Minnesota in 2008. Narrowleaf bittercress seeds can be spread by water, humans, animals, and equipment.

Refer to EDDMapS Distribution Maps for current distribution.

Don't be fooled by these look-alikes

  • Garlic mustard, Alliaria petiolata (invasive) – Garlic mustard and narrowleaf bittercress are both invasive plants in the mustard family that grow in forest understories and have white flowers with four petals. Narrowleaf bittercress leaves are composed of multiple leaflets while garlic mustard leaves are not divided into leaflets. Garlic mustard leaves on flowering stems are triangular.
  • Two leaved toothwort, Cardamine diphylla (native), cut-leaved toothwort, Cardamine concatenata (native) and other native Cardamine species – The native Cardamine species have larger flowers while narrowleaf bittercress flowers are small and often do not have petals. Narrowleaf bittercress has the small green growths called "auricles" that grasp the stem at the point where the leaf attaches to the stem and look like two small points extending away from the stem. The native Cardamine species do not have these auricles.
  • Wild parsnip, Pastinaca sativa (invasive) – Wild parsnip has yellow flowers and does not produce the long, slender seedpods of narrowleaf bittercress. Both wild parsnip and narrowleaf bittercress have a similar looking rosette stage (leaves in a round grouping near the ground). However, the leaflets on the narrowleaf bittercress rosettes are rounded and on small stalks, while the leaflets on wild parsnip rosettes are more oval shaped and attach directly to the stem.
 
Regulatory Classification

Narrowleaf bittercress is a Minnesota Department of Agriculture Prohibited Noxious Weed on the Control List meaning that efforts must be made to prevent the spread of seeds or other propagating parts. Additionally no transportation, propagation, or sale is allowed.

Threat to Minnesota
  • Narrowleaf bittercress forms dense cover in forest understories which may replace native species.
  • Impacts of narrowleaf bittercress are still under study. It has been classified as invasive in several eastern states.
What you should do

One way that invasive plant seeds and fragments can spread is in soil. Sometimes plants are planted purposefully. You can prevent the spread of invasive plants.

PlayCleanGo: Stop Invasive Species in Your Tracks

  • REMOVE plants, animals & mud from boots, gear, pets & vehicle.
  • CLEAN your gear before entering & leaving the recreation site.
  • STAY on designated roads & trails.
  • PLANT non-invasive species.
Native Substitutes
 
Control Methods

Mechanical control can be done by pulling the plant by hand or with equipment such as a shovel. Hand-pulling individual plants is effective if the entire root is removed.  Pulled plants can be kept on site for burning or piled and covered with a tarp for decay. Be sure to monitor the site and remove any plants that sprout from the burn or decay site. If plants must be moved off site, contact your local yard waste or compost site to see if they are equipped to compost at high enough temperatures to accept noxious weeds at their site. Transportation is only allowed to a disposal site and the Minnesota Department of Agriculture requires the load is protected in a manner that prevents the spread of noxious weed propagating parts during transport. It is illegal in Minnesota to dispose of plants in a landfill. See the Minnesota Department of Agriculture noxious weed disposal website for additional information.

Herbicide control can be done using a spot application of glyphosate or 2,4-D in early spring or late fall when native plants are dormant. These are systemic herbicides that are taken up by plants and move within the plant, which can kill leaves, stems, and roots.

Carefully and thoroughly clean off boots, clothes and tools before leaving the area to avoid carrying the tiny seeds to new sites.

Reporting

Report new occurrences by submitting a report through EDDMapS Midwest, emailing Arrest The Pest, calling Arrest the Pest (1-888-545-6684), or contacting your local county agricultural inspector.

Resources