By East Kootenay Invasive Species Society

Hoary Cress (also known as Heart-podded Hoary Cress or White Top) is a perennial invasive plant that thrives in open, sunny environments such as hayfields, meadows, and roadsides. Native to Eastern Europe and Western Asia, it spreads aggressively through both root systems and seed production, quickly outcompeting native vegetation.

Hoary cress primarily spreads via rhizomes and root fragments, forming dense patches of genetically identical clones that can extend over 12 feet. A single plant can produce up to 4,800 seeds annually, with two crops of seeds per year, and these seeds can remain viable in the soil for up to three years. It can expand its territory by as much as 3.5 m² per year.

Fun fact: Despite its invasive nature, hoary cress is surprisingly high in vitamin C!

How to Identify:

Hoary cress grows from 10-60 cm tall.

It has numerous white flowers with four petals each. These dense flower clusters give the weed a flat-topped appearance early in the season. Seed pods are heart-shaped.

Leaves on mature plants are hairy and shaped like arrowheads. Upper leaves on immature plants are typically hairless and clasp the stem.

Impacts:

Social Impacts: Hoary cress infestations can significantly reduce the quality of crops, pastures, and rangelands.
It limits forage availability for livestock and is commonly known to contaminate crop seed supplies.

The plant also exhibits allelopathic effects, which can inhibit the growth of wheat, barley, and various vegetable crops.

Ecological Impacts: Hoary cress threatens biodiversity by outcompeting and displacing native plant species.

Its fast-growing seedlings quickly absorb soil moisture, reducing water availability for native vegetation.

Management Strategies:

Mechanical/Manual Control: Hand-pulling can be effective for small or early-stage infestations, but only if the entire plant, including the root system is removed. Multiple weed pulls over several years may be necessary for successful eradication. For best results, pull plants when the soil is moist to reduce the chance of roots breaking.

Establishing competitive vegetation, such as perennial grasses or legumes, can help suppress Hoary cress by reducing available resources.

Soil cultivation can also slow the spread by disrupting root growth and preventing further expansion.

Chemical Control: Applying herbicide can be challenging since Hoary cress often occurs in crop fields, caution is needed to avoid damaging desirable plants. Glyphosate and 2,4-D have shown some success in controlling hoary cress. Always follow herbicide label instructions carefully before application.

Learn more.

The East Kootenay Invasive Species Council works to minimize the threat of invasive species that impact the environment, the economy and human health in the East Kootenay region of B.C., and we couldn’t do it without you! as a non-profit, we rely on grant funding and the generous support of our community to operate. Your donation will help us continue to protect the East Kootenay from invasive species. Donate here.

East Kootenay Invasive Species Society photos

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