Malus coronaria

This record represents Malus coronaria in the broad sense, following FNA (vol. 9, 2014) including M. angustifolia var. puberula, M. coronaria var. dasycalyx, M. glabrata, and M. glaucescens. In contrast, Kartesz (1994) treats M. coronaria var. coronaria, M. coronaria var. dasycalyx, M. angustifolia var. puberula, M. glabrata, and M. glaucescens as distinct.

Malus coronaria is a wide-ranging small tree or shrub found in open woods, forests, oak savannas, occasionally in bottomlands, forest edges, thickets, stream banks, alvars, fields, fencerows, and roadsides. It occurs in eastern North America from southern Ontario, Canada, south through the Great Lakes region to Georgia west to Louisiana. There are over 400 estimated occurrences, which face threats from habitat loss and fragmentation, rights-of-way maintenance, mammal and insect herbivory, hybridization with cultivated apples, and climate change. Little is known about trends. Research is needed to better understand the validity of the purported three Malus taxa in eastern North America, impact of hybridization on native taxa, and threats from nonnative insects.

Malus coronaria occurs in eastern North America from southern Ontario, Canada, south through the Great Lakes region to Georgia west to Louisiana (FNA 2014, Roulston et al. 2025, Weakley and the Southeastern Flora Team 2025). Range extent was estimated to be over 1.5 million square kilometers using herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1994 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 1994 and 2025, it is estimated that there are over 400 occurrences rangewide (GBIF 2025, iNaturalist 2025, NatureServe 2025, RARECAT 2025, SEINet 2025). This species may be cultivated, and occurrence data was not thoroughly evaluated for evidence of cultivation. Also, difficulty distinguishing this species from other native taxa in eastern North America (M. angustifolia and M. ioensis) may result in an underrepresentation of true abundance.

Native Crabapples (Malus) in North America face numerous threats. Habitat loss and fragmentation has been the highest threat over time, with additional threats from rights-of-way maintenance, mammal and insect herbivory. New, emerging threats from nonnative insects, hybridization with cultivated apples, and climate change have unknown impacts on future impacts to native Malus populations.

Mammal herbivory has been documented in native populations of Malus in North America. Large mammals, such as deer, moose, and elk, eat nearly all parts of Malus plants, including flowers, fruits, leaves, twigs, and bark; at elevated densities, large mammals can negatively affect populations of Malus by preventing recruitment (Roulston et al. 2025). Small mammals, such as rabbits, hares, squirrels, voles, mice, and porcupines, consume Malus seedlings (Sutton et al. 2014 in Roulston et al. 2025).

Insect herbivory has also been documented in Malus populations. Many insects, including approximately 15% of over 12,000 butterfly and moth species in the United States, use Malus as a host plant (Narango et al. 2020). Most insect herbivory damages leaves, which may reduce photosynthesis but is rarely lethal (Roulston et al. 2025). However, internal insect pests, living within and feeding upon the vascular system of plants, may more acutely impact tree health. There are both native (e.g., Round-headed Apple Tree Borer (Saperda candida, Coleoptera: Cerambycidae)) and nonnative insect pests (e.g., Black Stem Borer (Xylosandrus germanus, Coleoptera: Curculionidae)) that feed on the phloem of Malus (Roulston et al. 2025). Impacts of rapidly expanding nonnative insects, such as Brown Marmorated Stink Bug (Halyomorpha halys Stål, Hemiptera: Pentatomidae), Japanese Beetle (Popillio japonica Newman, Coleoptera: Scarabaeidae), and Spotted Lanternfly (Lycorma delicatula White, Hemiptera: Fulgoridae), on wild populations of Malus is largely unknown.

Wild populations of Malus also face threats from introduced genetic material from hybridization with cultivated plants. While the introgression between M. coronaria and cultivated Malus has been quantified in southern Ontario, rangewide impacts are unknown (see references in Roulston et al. 2025). However, hybrid plants do not appear to live to reproductive age or reproduce, possibly due to higher mortality of hybrid plants. Hybridization can lead to population reductions through limiting reproduction, increasing proportions of asexual plants in populations, and decreasing genetic integrity and therefore resilience of plants, impacting their long-term survival.

Climate change is likely to have a strong impact on Malus populations. The life history of Malus species, as woody perennials with long generation times and extended juvenile phases, may inhibit adaption to climate change. Milder winters may reduce cold hardiness, shifting to earlier timing of plant phenology (such as earlier flowering, potentially mismatching with pollinator availability), increasing damage to flowers or flower buds from late-spring frosts, and increasing abundance or expanding distribution of pests and pathogens (Roulston et al. 2025). Alteration in rainfall patterns and water availability during the growing season may lead to increased droughts or prolonged wetness (Volk et al. 2015a). Range shift models predict poleward expansion to entirely new ranges by 2070 (Roulston et al. 2025).