Crataegus monogyna
(hawthorn)

Preferred Common Name

• hawthorn

Other Scientific Names

• Crataegus aegeica Pojark
• Crataegus alutacea Klokov
• Crataegus azarella Griseb.
• Crataegus boissieri Willk.
• Crataegus brevispina Kunze
• Crataegus calycina Peterm. subsp. calycina
• Crataegus calycina Peterm. subsp. curvisepala (Lindm.) Franco
• Crataegus ceratocarpa Kossych
• Crataegus granatensis Boiss.
• Crataegus laciniata sensu Willk., non Ucria
• Crataegus lasiocarpa Lange
• Crataegus leiomonogyna Klokov
• Crataegus lipskyi Klokov
• Crataegus maura auct. hisp., non L.f.
• Crataegus oxyacantha L., nom. ambig.
• Crataegus oxyacantha L., nom. ambig. subsp. oxyacantha
• Crataegus oxyacantha var. praecox hort. ex Loudon
• Crataegus panachaica C.K.Schneid.
• Crataegus popovii Chrshan.
• Crataegus praearmata Klokov
• Crataegus transalpina A.Kern.
• Crataegus triloba auct., non (Poir.) Pers
• Mespilus monogyna (Jacq.) All.
• Mespilus oxyacantha (L.) Crantz

International Common Names

• English: European hawthorn; May tree; May-tree; oneseed hawthorn; one-seeded hawthorn; single-seed hawthorn; whitethorn
• Spanish: espino albar
• French: aubépine a un style; aubépine monogyne
• Russian: boyaryshnik odnopestnyi
• Portuguese: pirliteiro

Local Common Names

• Czechoslovakia (former): hloh jednosemenny
• Germany: Eingriffeliger Weissdorn; Eingriffliger Weissdorn; Saulenweissdorn
• Italy: biancospino; cratego monogino
• Netherlands: eenstijlige Meidoorn
• Poland: glog jednoszyjkowy
• Sweden: trubbhagtorn
• UK: common hawthorn; single-seed hawthorn
• USA: European hawthorn; singleseed hawthorn

EPPO code

• CSCMO (Crataegus monogyna)

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Rosales
•                         Family: Rosaceae
•                             Genus: Crataegus
•                                 Species: Crataegus monogyna

The genus Crataegus, part of the Rosaceae family (subfamily Maloideae), contains over 200 species, though some taxonomists divide these further and they may be over 1000 species depending on the descriptions followed. Several varieties and forms have been proposed, and European species are described and defined by Christensen and Janjic (2006). A number of subspecies are also recorded: subsp. monogyna (Royal Botanic Garden Edinburgh, 2007) from France to southern Ukraine, subsp. aegeica (Pojark.) Franco in the eastern Aegean, subsp. azarella (Griseb.) Franco in southeastern Europe (southern and eastern Spain and Italy, also Sicily), subsp. brevispina (Kunze) Franco in Portugal, Spain and the Balearic islands, subsp. leiomonogyna (Klokov) Franco in Russia, and subsp. calycina (Peterm.) Soó and subsp. intermedia (Fuss) Jáv. (ranges not stated).

Crataegus spp. are commonly known as the hawthorns, though species-specific vernacular names may be applied to several species, such as English hawthorn and white thorn being applied to both Crataegus monogyna and Crataegus laevigata. It is also not impossible that some introduced populations will in future be attributed to C. laevigata and not C. monogyna, and also that new spontaneous hybrids will develop in introduced ranges with both exotic and native Crataegus species as parents. The ‘haw’ in hawthorn is the name of the fruit. Many species are able to freely hybridize, further increasing variability and speciation. Being a valued ornamental, horticultural selections have also been made, and there exist a large number of cultivars.

C. monogyna is a thorny shrub or small tree up to 10 m high though commonly 2-6 m, with smooth pale grey bark. Branches straight with stout spines on branches; leaves alternate, ovate to obovate, 1.5-3.5 cm long, 3-7-lobed, margins entire or sparingly serrate, mostly glabrous except for patches of hairs in axils of veins on the underside. Flowers white fading to pink, in clusters, petals 5, styles 1. Fruit single-seed red berries, 1.25 cm in diameter.

It has been widely introduced, is commonly planted and has become naturalized in North America, southern Africa, Australia and New Zealand having been introduced to each sometime in the 1800s. It has been observed to be an aggressive colonizer (Bass, 1990; Williams et al., 1986), and has become an invasive species in the Pacific northwest of the USA (Oregon and Washington), also British Columbia, and it was recently noted as fully naturalized and a potential pest in northern California, USA (Hrusa et al., 2002). It is also one of six woody invasive species in New York, USA, by Hunter and Mattice (2002), and noting its widespread distribution in North America (USDA-NRCS, 2007), further invasion in other states and provinces is highly likely. C. monogynais also invasive in South Africa, where birds are aiding spread in the Eastern Cape (Reichard et al., 2001). It is very invasive in northern New South Wales, having spread rapidly and conspicuously throughout the region and elsewhere in southern Australia at rates of 80–120 m yr^-1 (Bass et al., 2006), and it is an environmental weed of concern in New Zealand, having been introduced in 1899 (Owen, 1996).

Soil drainage

• free

Soil reaction

• acid
• neutral

Soil texture

• heavy
• medium

Special soil tolerances

• infertile
• shallow

The principal means of long-distance dispersal has been its intentional introduction as an ornamental/landscaping and hedging/boundary plant. For these reasons, it was introduced to North America, South Africa and Australasia, and further introduction may be likely.

There are clear positive impacts from the propagation and sale of C. monogyna and its many cultivars as ornamental plants, and also for the sale of seedlings or cuttings from commercial forestry nurseries for planting as hedges or in general landscaping. However, no exact data as to its economic contribution are forthcoming, and it may be expected that such exact figures would be difficult to estimate. Negative impacts are also increasing likely in the form of control programmes in natural areas of North America and Australasia where it is becoming a problematic invasive weed.

In addition, due it acting as a host for crop pests and pathogens or pests, it should not be planted near some crops, such as fruit trees and hops (Puszkar, 1981; Zajaczkowski, 1998).

Hawthorn's thickets are shelters for many birds and little mammals, therefore, they are important for nature protection purposes, especially on agricultural or urbanized grounds.

However, where invasive, it displaces native plants, and dense thickets alter the structure of the forest understory and can make the movement of large animals difficult. Some species of Crataegus contain hydrocyanic acid in the leaves, which is poisonous to cattle, though the presence of this in C. monogyna is not yet known. Birds may prefer its berries to those of native berried plants, which may cause a reduction in the regeneration of native plants. Also, the ability of C. monogyna to hybridise with native species of Crataegus, means that there will be genetic pollution of the indigenous gene pool over time in invaded areas.

One nature preserve in Willamette Valley, Oregon, USA, has had to be abandoned because C. monogyna has invaded and there are not adequate resources to control it (Alverson and Sigg, 2008), and there is also a specific threat to the Garry Oak ecosystem of British Columbia, Canada.

• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Highly adaptable to different environments
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
• Pioneering in disturbed areas
• Highly mobile locally
• Long lived
• Has high reproductive potential
• Reproduces asexually
• Has high genetic variability

• Changed gene pool/ selective loss of genotypes
• Ecosystem change/ habitat alteration
• Modification of successional patterns
• Monoculture formation
• Reduced native biodiversity
• Threat to/ loss of endangered species
• Threat to/ loss of native species

• Competition - monopolizing resources
• Competition - shading
• Pest and disease transmission
• Hybridization
• Interaction with other invasive species
• Pollen swamping

• Highly likely to be transported internationally deliberately
• Difficult to identify/detect as a commodity contaminant
• Difficult to identify/detect in the field

C. monogyna is often planted in hedges and shelterbelts on farms and as an ornamental shrub or small tree in towns and cities and has been successfully used in revegetation and land reclamation of wastelands and mine spoils (Kluczynski, 1981; La Marca et al., 1998) as well as on polders in Holland (Peeters and Stuurman, 1981). The species is relatively tolerant to air pollution (Hirka, 1992) and as such seems to be particularly convenient for planting along roads and motorways. The spines deter grazing animals, and the plant is regarded as an impenetrable barrier to grazing. Seeds require stratification before sowing in spring, and 1-2-year-old seedlings or cuttings are used, the latter best in gaps within old hedges.

The wood of C. monogyna is narrow-ringed, extremely hard and durable and is sometimes used for the production of various small objects. The possibility of its utilisation for other purposes is limited by its low speed of growth. The flowers and fruits of hawthorn have been used in folk medicine for a long time and are now regarded as a precious raw material in production of important drugs to combat heart disease (e.g. Iwamoto et al., 1981), hypertension and allergies. The fruits of C. monogyna contain many vitamins, and are widely collected and consumed in some rural areas where native.