Key to the Trees of Wisconsin

Crataegus: hawthorns or thornapples

Crataegus is a large genus of trees and shrubs with fruits similar in appearance to small apples (Malus pumila), and in most cases with conspicuous thorns on the branches. The taxonomy of Crataegus remains unsettled. It appears that various aspects of reproduction in this genus have resulted in numerous distinctive local populations difficult to relate to others, and botanists have probably recognized more species than actually exist. There does not appear to be a workable method of identifying the species based on vegetative characters. Indeed, all credible keys for our area require that individuals be tagged and revisited so that flowers, fruit and mature leaves can be collected before identification is possible. The list below includes all (17) species of Crataegus judged to be of tree form in Wisconsin. Fourteen of these species generally have at least shallow lobes in addition to teeth on the leaf margins. C. crus-galli and C. punctata, (and sometimes C. succulenta) are toothed, but usually unlobed. An additional 23 species of Crataegus reported for Wisconsin are deemed to be shrubs and are not listed here.

Few, if any, current botanists in Wisconsin claim thorough knowledge of Crataegus, and I offer no new insights to the means of recognizing species here. In my experience, the number of individual plants of Crataegus is far greater in the southern half of the state, north to Brown County. In Brown County Crataegus is widespread and numerous, especially in disturbed, sunny locations, including consistently grazed areas where the competing plants are apparently diminished by the cattle, and Crataegus and its thorns are left to prosper. The most common species in Brown County appears to be C. mollis and it is apparently the first species to flower in this area each spring. C. punctata is also common and C. crus-galli is widely planted. North of Green Bay, in northeastern Wisconsin C. chrysocarpa appears well distributed, though not usually numerous. Several other species are currently under observation, but I can offer no further insight into the Crataegus of Wisconsin based on my own observations.

The following list includes all 17 tree species of Crataegus reliably reported for Wisconsin.

Latin name common name

Crataegus beata Sarg.

Dunbar's hawthorn
Crataegus calpodendron (Ehrh.) Medik. sugar hawthorn, pear hawthorn
Crataegus chrysocarpa Ashe fireberry hawthorn, round-leaved hawthorn
Crataegus crus-galli L. cockspur hawthorn
Crataegus dodgei Ashe Dodge's hawthorn
Crataegus douglasii Lindl. black hawthorn
Crataegus flabellata (Bosc ex Spach) K.Koch fan-leaf hawthorn
Crataegus holmesiana Ashe Holmes' hawthorn
Crataegus irrasa Sarg. Blanchard's hawthorn
Crataegus margaretta Ashe Margarett's hawthorn
Crataegus mollis (Torr. & A.Gray) Scheele downy hawthorn
Crataegus monogyna Jacq. one-seeded hawthorn
Crataegus pedicellata Sarg. scarlet hawthorn
Crataegus pruinosa (H.Wendl.) K.Koch frosted hawthorn, waxy-fruit hawthorn
Crataegus punctata Jacq. dotted hawthorn
Crataegus schuettei Ashe Schuette's hawthorn
Crataegus succulenta
fleshy hawthorn

Based on distribution maps from the University of Wisconsin-Madison, derived from confirmed specimens from several Wisconsin herbaria, relatively common tree species of Crataegus include C. calpodendron (southern WI), C. chrysocarpa (throughout WI, but more records from the south) , C. holmesiana (SE WI), C. mollis (common in SE), C. pedicellata (mostly SE), C. pruinosa (mostly southern 3 tiers of counties), C. punctata (southern ¾), C. schuettei (eastern) and C. succulenta (mostly southern, but a few north).

For those brave enough to pursue further identification of Crataegus specimens in Wisconsin, the following works will prove valuable.

Kruschke, Emil P. 1965. Contributions to the Taxonomy of Crataegus. Milwaukee Public Mus. Publ. Bot. 3. 273 pp.

Voss, E.G. 1985. Michigan Flora. Part II. Dicots (Saururaceae-Cornaceae). Cranbrook Inst. of Sci. Bull. 59 & Univ. Mich. Herb. 724 pp. Crataegus covers pages 386-418.


Glossary of terms

Return to start of tree key

Return to list of tree species

Contact the author