Crataegus macrosperma

Kartesz (1999) includes Crataegus fluviatilis (= C. apiomorpha) in C. macrosperma, while Kartesz (1994) and FNA (vol. 9, 2014) here treat them as distinct.

Crataegus macrosperma is a wide-ranging shrub or tree found in old fields, pastures, fencerows, brush, open woods, wooded slopes, mesic to subxeric hardwood forests, rock outcrops, montane balds, and rocky slopes and summits. It occurs in eastern North America from the United States in Minnesota through the Great Lakes region and the St. Lawrence Valley to southern Newfoundland in Canada, south to Arkansas, and in the Appalachians to northeastern Alabama. There are over 300 occurrences. This species is moderately and possibly highly threatened across its range due to disease but also the conversion of habitat for other land uses. More information on the distribution, abundance, and threats are needed to better understand the extinction risk of this species. Continued specimen collection for expert identification, and herbarium work is needed to confirm identification of specimens, as well as digitization and georeferencing.

Crataegus macrosperma occurs in eastern North America from the United States in "north-central Minnesota through the Great Lakes region and the St. Lawrence Valley to southern Newfoundland [in Canada] south to Arkansas, and in the Appalachians, to northeastern Alabama," and it is "particularly common in the Appalachians" (FNA 2014, Weakley and the Southeastern Flora Team 2025). Range extent was estimated to be over 2.7 million square kilometers using herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1984 and 2025 (GBIF 2025, iNaturalist 2025, NatureServe 2025, RARECAT 2025, SEINet 2025).

By applying a 1 km separation distance to herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1984 and 2025, it is estimated that there are over 300 occurrences rangewide (GBIF 2025, iNaturalist 2025, NatureServe 2025, RARECAT 2025, SEINet 2025).

Like most Crataegus, this species is susceptible to blight and fungal rusts which can cause stem cankers and dieback, as well as inhibit seed production. Fungal rusts are especially problematic when the alternate host, Eastern Red Cedar (Juniperus virginiana) is prolific in the vicinity (Lance 2014). Aggressive, invasive woody species, such as Lonicera japonica and Rhamnus cathartica, outcompete hawthorns and other natives, shifting the composition of the habitat such that native biodiversity is reduced, often eliminating hawthorns from these altered communities (e.g., Catling and Mitrow 2012). This species is also threatened by densification/mesophication of open woodland habitat (Nowacki and Abrams 2008) and conversion of natural woodlands to human uses. Plants growing in pastures are tolerant of browsing; while new growth may be consumed by cattle, spines deter further browsing (Lance 2014). The Asian Longhorned Beetle (Coleoptera: Cerambycidae, Anoplophora glabripennis) can use Crataegus for larval hosts, though Acer, Populus, Salix, and Ulmus are preferred (Meng et al. 2015). Modeling changes in range size with habitat shifting due to climate change had mixed results, with some hawthorns expected to have range expansions and other species expected to have no change or range contractions (Naghiloo and Vamosi 2023).