Valuable landscape trees, hawthorns (Crataegus spp.) have one major drawback: thorns. The 1- to 3-inch thorns on most hawthorns can inflict nasty scratches. This makes them useful as barrier hedges but difficult to use as landscape trees, which is a shame since they're lovely trees. Several thornless varieties are available that are more gardener-friendly.
Cockspur hawthorns (C. crusgalli) get their name from their curved thorns that resemble the heel spurs on roosters. The thornless variety, sold as either C. crusgalli var. inermis (inermis means thornless) or as the cultivar Crusader (Cruzam), is completely thornless on both the trunk and branches. It's a small tree, rarely over 15 feet in height and spread. Thornless cockspur hawthorns are covered in white flowers in late spring and have orange fruits in fall that persist well into winter. Fall leaf color is bright gold. Crusader hawthorns are also resistant to rust, a fungal disease that can damage hawthorns.
Princeton Sentry Hawthorn
A native American tree, Washington hawthorn (C. phaenopyrum) is a four-season tree. Spring brings fragrant white flowers, summer has clean green foliage for cool shade, fall foliage color is orange to scarlet to purple and the winter fruit display persists for months. Princeton Sentry is a columnar form of Washington hawthorn that's nearly thornless.
Winter King Hawthorn
Winter King hawthorn is a common cultivar of the green hawthorn (C. viridis), another native tree. Growing in a distinct vase shape, Winter King has large fruits and red fall color. The name comes from the exuberant display of bright red fruit during the winter. Although technically not inermis, it has few thorns, particularly as it ages.
You may have to search a bit to find Pygmaea hawthorn, a thornless cultivar of the singleseed hawthorn (C. monogyna), the sweetest-scented of all the hawthorns. Pygmaea is also sold as Inermis Compacta. It's a small, mushroom-shaped tree with no thorns.
Ohio Pioneer Hawthorn
The dotted hawthorn (C. punctata) can be grown as a tree or large shrub. The white spring flowers are followed by deep yellow to dull red fruit that are conspicuously dotted, hence the common name. Ohio Pioneer is a thornless cultivar discovered at the Secrest Aroboretum in Wooster, Ohio. It's similar in habit to the species, with good fall fruiting.