Flower:

Flat-topped, branching cluster of 10 to 30 flowers at tips of branch twigs, emerging after the leaves in mid to late spring. Flowers are ½ to ¾ inch across with 5 round white petals. In the center are 6 to 10 stamens; stamen tips (anthers) can be either pink or white and are 1 to 1.4 mm long.

The 5 sepals around the base of the flower are narrowly triangular, the edges usually with gland-tipped teeth or narrow gland-tipped lobes. The cup-shaped hypanthium below the sepals and flower stalks are both usually covered in soft hairs, though may become hairless.

Leaves and stems:

Leaves are alternate, 1½ to 3½ inches long, up to about 2½ inches wide, broadly elliptic to somewhat diamond-shaped in outline, widest near or above the middle, blunt to pointed at the tip, mostly wedge-shaped at the base but may be somewhat rounded. Edges are toothed except near the base; the 2 to 4 shallow lobes per side are often obscure. The upper surface is sparsely covered in stiff, appressed hairs, the lower usually hairy along major veins. The leaf blade tapers at the base to a narrowly winged stalk up to about ¾ inch long that lacks glands and may be hairy only on the upper surface; the wing does not usually extend to the base of the stalk.

Young twigs are hairless, shiny reddish to brown, turning gray the 3rd year and developing slightly curved thorns 1½ to 4 inches long. Thorns are usually abundant and are shiny dark reddish-brown when young.

Mature bark is thin, gray to gray-brown and splits into narrow plates. Stems are single or a few from the base and may reach 6 inches in diameter on larger stems. Compound thorns are sometimes present on lower stems; branches are spreading to ascending. Plants are not colony-forming or root suckering.

Fruit:

Fruit is fleshy and berry-like, round, about 3/8 inch diameter, dull to somewhat shiny red at maturity, hairy or hairless.

Notes:

Large-thorned Hawthorn is the most common Hawthorn in North America and found across Minnesota in a variety of habitats and soil conditions, but primarily in forest and woodland edges and old pastures where it receives some sun.

Large-thorned Hawthorn is recognized by the combination of: single or few-stemmed shrub or small tree, sometimes with compound thorns; spreading to ascending branches with abundant slightly curved thorns up to 4 inches long; leaves often obscurely lobed, wedge-shaped at the base, toothed except near the base, usually hairy on major veins on the underside; short, winged leaf stalks that lack any glands, hairless on the back; flowers with 6 to 10 stamens and white or pink anthers; sepals with gland-tipped serrations or narrow lobes, hypanthium and flower stalks usually hairy. Fruit is round, dull or somewhat shiny red at maturity. The thorns are the largest of the Minnesota Hawthorns, a trait it shares with the very similar Crataegus succulenta (Fleshy Hawthorn).

Some references do not recognize the Crataegus macracantha found in Minnesota as a separate species, but lump it with C. succulenta, sometimes as var. macracantha. The typical C. succulenta has flowers with about 20 stamens and tiny (less than 1mm long) white or pink anthers but is otherwise essentially identical; its range, according to Welby Smith's book “Trees and Shrubs of Minnesota”, is also mostly limited to the southeast counties and the Twin Cities Metro area, though herbarium records have it all over the state. Those records should be reviewed to determine the current taxonomy as published by Flora of North America and accepted in Minnesota.

C. macracantha may be confused with C. chrysocarpa (Fireberry Hawthorn), the most common Hawthorn in the state, which never has compound thorns, usually has at least a few glands on leaf stalks, and leaves tend to consistently have more distinct lobes, are somewhat smaller and rounder in outline.