Hawthorn
Crataegus spp.

Introduction

Hawthorn is a large shrub or small tree, often growing in large, dense thickets. Generally it occurs on moist, deep, fine-textured soils. Although predominantly an understory species, it also forms pure stands. It does not typically grow on disturbed sites. Hawthorn thickets provide both food and cover for wildlife. The species stabilizes soil and stream banks very well (Habeck 1991). The spines of hawthorn were used by first peoples as needles and fishhooks (Turner 1979). There is confusion about the taxonomy of species in the genus Crataegus (Phipps 1998a). Crataegus spp. have undergone great diversification and rapid evolution, facilitated by forest clearing (making new habitats available), polyploidy and apomixis (asexual reproduction via seed) (Lauriault 1989), not just on the American continent but also in Eurasia. As a consequence of this taxonomic confusion, much of the information about the distribution of various Crataegus species, as well as reports about existing varieties, may be inaccurate. According to Parish et al. (1996), Douglas (or ‘black’) hawthorn (C. douglasii) is the most common species in the southern interior of British Columbia. Columbia (‘red’) hawthorn (C. columbiana) is less common. In coastal British Columbia, Pojar et al. (1994) report Douglas hawthorn as common and C. monogyna as less common. Brayshaw (1996) mentions four species: C. columbiana, C. douglasii, C. suksdorfii, and C. monogyna. The latter, a commonly planted native of Europe, has escaped and become common and even weedy on bare ground near urban areas. The following five species of Crataegus, not included in any available floras, are reported as new to British Columbia: C. chrysocarpa, C. macracantha, C. phippsii, C. okanaganensis and C. okennonii (Phipps 1998b; Phipps and O’Kennon 1998). None of them are endemic to the province, but no one knows how rare they are. Since Douglas hawthorn is the most common species, the information about hawthorn regeneration is specific to this species, although, presumably, not too wildly different for the other species.

The most widespread occurrence of Douglas hawthorn is in the central and south of the Pacific region, from southeastern Alaska to northern California. The species also occurs central in the Cordilleran Region, down to Colorado, with isolated areas further east in the Great Plains (Little 1976). Columbia hawthorn, according to Little (1976), has a limited and scattered distribution in the interior of British Columbia, in Alberta, Washington, Oregon, and Idaho.

Distribution and Protected Areas – from Hamann et.al. 2005

Conservation Status Summary – from Chourmouzis et.al. 2009

“Crataegus spp.occurred at such low frequency in the data set that estimated protection levels are low or near zero in all zones except the IDF. Verification is recommended in the BG, CDF, CWH, and even the IDF zones, but not in the ICH and PP zones, where occurrence is particularly low. It is recommended that conservation efforts be directed first to the BG zone. Crataegus spp. observations could represent one of six proposed native black-fruited hawthorns. We suggest that the taxonomic complexity and the presence of this early-seral species in rural settings, modified habitats, and smaller regional or district parks be addressed when determining the conservation needs for this species group. Also, a comprehensive re-evaluation of protection status and conservation needs for this species in the CDF zone is recommended prior to field verification in the zone.”

Reproduction

Douglas hawthorn produces many fertile seeds. The interval between good seed crops is one to two years (Banerjee et al. 2001). After removal of stems it will re-sprout and sucker from the root system. Habeck (1991) reports difficulties in seedling establishment and slow growth. Our own survey of its occurrence in British Columbia has yielded no results to date. Since C. monogyna has been reported to hybridize with C. suksdorfii in Oregon (Brayshaw 1996), there may be some concern for the introduction of foreign material.

Genetic structure

Hitchcock and Cronquist (1961) report three varieties: var. douglasii, var. rivularis and var. suksdorfii. The latter is probably a different species (Brunsfeld and Johnson 1990). Considering the taxonomic confusion mentioned above, a re-evaluation of the whole Crataegus genus, using molecular systematic methodology, is in order.

Resource management and seed transfer

No information available.