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Noxious weeds

King County, Washington

To offer a suggestion or report an error on the King County Noxious Weeds website, please contact Sasha Shaw, education specialist.

Common hawthorn
Crataegus monogyna 

Common hawthorn - Crataegus monogyna - click for larger imageCommon hawthorn, also called oneseed or single-seed hawthorn, is an introduced tree that has naturalized in the Pacific Northwest.  This small tree spreads readily by seed into woodlands and open fields, often creating a dense, thorny thicket.  Its abundant red berries are attractive to birds and other animals, which help spread this tree far beyond where it is planted.

In King County, Washington, common hawthorn is classified as a Weed of Concern and its control is recommended in natural areas that are being restored to native vegetation and in protected forest lands and wilderness areas. Common hawthorn can also be a nuisance species in pastures and wildlife grazing areas and its removal from those areas is also recommended. Common hawthorn is not on the Washington State Noxious Weed List and there is no restriction on its sale or use in landscaping.

Identification (see below for more photos)

  • Thorny, deciduous small tree or shrub, 6 to 30 feet tall
  • Leaves 3 to 7-lobed, 1-2 inches long and nearly as broad, resemble mittens or paws
  • Flowers grouped in broad, dense, flat-topped clusters and resemble cherry or apple blossoms
  • Petals are usually white, sometimes pink
  • Common hawthorn - Crataegus monogyna - click for larger imageFruit is a round, crimson berry that often persists into late winter 
  • Similar to English hawthorn (Crataegus laevigata) and other ornamental hawthorn species and often forms hybrids that have intermediate characteristics

Reproduction and spread

  • Berries are dispersed by birds and other animals
  •  A single tree can produce over 2,000 berries
  • Flowers in spring and develops fruit in the fall; berries often persisting into the winter
  • Seeds passing through an animal aids germination but isn't necessary
  • Germination occurs primarily in spring
  • Most vegetative growth occurs in spring and early summer, and normal growth rate is one to two feet a year

Impacts and distribution

Common hawthorn - Crataegus monogyna - click for larger imageCommon hawthorn is carried by birds into forests and open fields where it can form dense, thorny thickets that outcompete native species and make passage of large animals difficult. Somewhat tolerant of shade as well as drought, common hawthorn invades both open fields and woodlands in Washington, Oregon and California. Common hawthorn has naturalized on both coasts of North America and in many of the states in central and eastern United States, as well as parts of Australia, New Zealand and South Africa. Although more common west of the Cascades, common hawthorn has spread in eastern Washington as well.

Common hawthorn is generally a forest understory species in its native range, but in our region its grows well in a wide range of habitats.  Riparian areas, abandoned fields and pastures, shrublands and grasslands, oak woodlands, and other forested habitats are all vulnerable to invasion by common hawthorn.

Introduced starting in the 1800's, common hawthorn appears to have begun spreading first in Oregon and southern Washington.  Naturalized specimens were collected in Oregon in the early 1900's and one collection from Wahkiakum County, Washington in 1927 notes that the species was commonly established along roadsides.  For more information on common hawthorn distribution, see the UW Burke Museum website.

Control

  • Common hawthorn - Crataegus monogyna - click for larger imageSeedlings and young saplings can be pulled or dug up when soil is moist, but roots quickly become deep and stout and sharp thorns are present even on young seedlings.
  • Mature trees have deep and extensive roots so digging is labor-intensive and results in considerable soil disturbance if all of the roots are removed.
  • Common hawthorn often stump-sprouts, so removal by cutting alone is not usually effective.
  • Applying herbicide with the cut stump or frilling method is probably the most effective approach for plants that cannot be removed by digging or grubbing out the roots. Foliar herbicide treatment is another option but may result in spray drift to desireable vegetation.

What to do if you find this plant

Because common hawthorn is already naturalized in many places in King County and is not on the State Noxious Weed List, we are not tracking locations. Common hawthorn - Crataegus monogyna - click for larger imageHowever, if you know of any heavily infested natural areas in state or federal forests or other remote natural areas, we would be interested in having that information. We are also gathering information on effective control methods. If you have had any success (or failures) controlling this plant, please contact our office.  Please note that common hawthorn is legal to sell and plant in Washington.

Common hawthorn photos - click thumbnail for larger image

 

Common hawthorn - Crataegus monogyna - trunk - click for larger image Common hawthorn - Crataegus monogyna - leaves - click for larger image Common hawthorn - Crataegus monogyna - flowers - click for larger image Common hawthorn - Crataegus monogyna - flowers and berries - click for larger image

Some of the photos on this page are courtesy of Ben Legler. Please do not use these images without permission from the photographer.  Other photos not otherwise labeled may be used for educational purposes, but please credit the King County Noxious Weed Control Program.

More information on common hawthorn

Related information

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Program offices are located at 201 S. Jackson St., Suite 600, Seattle, WA 98104. To contact staff, see the Noxious Weed Control Program Directory, send an email, or call 206-477-WEED (206-477-9333).