Hawthorn (Crataegus): how to identify it

Common hawthorns in the United States

North America is the center of hawthorn diversity: Virginia Tech notes that the USDA PLANTS Database lists 216 species, and that hybrids make the genus confusing even for botanists. These four are the ones you are most likely to meet in yards, parks and the woods of the eastern half of the country.

Cockspur hawthorn is the easiest to name: the Morton Arboretum's cockspur profile gives thorns 2 to 3 inches long and glossy, unlobed leaves rounded at the tip and narrowed toward the base. It grows 20 to 30 feet tall and wide. A thornless variety (var. inermis) is widely planted, so a smooth-twigged tree with those leaves can still be a cockspur.

Washington hawthorn has small, triangular leaves with three to five toothed lobes, more like a tiny maple leaf than a typical hawthorn, and turns red to purple in fall, according to the Morton Arboretum. Its red fruits hang on into winter.

Downy hawthorn is a Midwest tree whose leaves are "very hairy early in the season" (Morton's downy hawthorn profile); rub a young leaf and it feels soft.

Green hawthorn is a southeastern native of lowlands, valleys and swamps. The University of Maryland Extension describes its planted cultivar 'Winter King' as tolerant of city conditions, with small, inconspicuous thorns, orange-red fruit that persists into winter, and, on mature trees, patches of gray outer bark that shed to show orange inner bark. That bark is a good winter mark for 'Winter King' along streets and in parking lots.

Common hawthorn in the UK and Ireland

In Britain and Ireland, "hawthorn" almost always means common hawthorn (Crataegus monogyna), the thorny tree that makes up much of the hedgerows that divide fields. The guide to identifying British trees covers the other hedgerow and woodland trees. The Woodland Trust lists its other names: May tree, whitethorn, quickthorn and one-seed hawthorn. Cut as a hedge it stays a dense shrub; left alone it grows into a small tree of about 15 m (50 ft) with brown-grey, knotted, fissured bark.

Four checks, in this order:

• Leaves: about 6 cm (2 1/2 in) long, with toothed lobes cut at least halfway to the midrib, so the leaf looks deeply lobed. They are often among the first leaves to open in spring.
• Flowers: white, occasionally pink, highly scented, five petals, in flat-topped clusters in May, which is where the name May tree comes from. Each flower has a single stigma.
• Haws: deep red, each with one seed. That single seed is the quickest test against Midland hawthorn.
• Winter twigs: slim, brown and thorny, with each spine growing from the same point as a bud.

Midland hawthorn (C. laevigata) is the look-alike. The Woodland Trust's Midland hawthorn page describes glossy, three-lobed leaves 2 to 6 cm long with shallow lobes cut less than halfway to the midrib, flowers with two stigmas from mid-April (one to two weeks before common hawthorn), and oval red haws with two seeds. It favors ancient woodland and clay hedgebanks and is most common in central and southern England, uncommon in Wales, Scotland, south-west England and East Anglia. The two species hybridize, so some hedge trees sit in between.

Common hawthorn in Ireland. University College Cork's Tree Explorers describes common hawthorn as native to Ireland, where its Irish name is sceach geal, "bright thorn". Its leaves have three to five deep, slightly toothed lobes; the white blossom comes around mid-May; the haws form in July and August and ripen deep red in autumn and early winter. Hawthorn hedges are a common feature of the Irish landscape: UCC dates hedge laying to the mid-seventeenth century in the Pale around Dublin, spreading across Ireland from the mid-eighteenth century, and calls the thorny hedge "stock-proof".

UCC also records hawthorn's place in Irish folklore. It is best known as a fairy tree, especially a lone hawthorn standing in a field, and many stories warn that harming one brings misfortune. It was thought bad luck to bring any part of the tree into the house. In 1999, storyteller Eddie Lenihan objected to cutting a lone hawthorn on the route of the Newmarket-on-Fergus bypass in County Clare, and the road was routed around it. A lone thorn in the middle of a field is therefore often a tree someone chose not to cut.

Hawthorn look-alikes and how to rule them out

Blackthorn (Prunus spinosa) shares British hedges with hawthorn and is just as spiny. The Woodland Trust gives the winter test: hawthorn spines come from the same point as a bud, while blackthorn has its buds on the spines.

Callery pear, including the wild offspring of the Bradford cultivar, forms thorny thickets along American roads and field edges. Its leaves are glossy and unlobed, and it blooms in a sheet of white very early in spring, before or with the leaves. Virginia Tech lists it among hawthorn's look-alikes; the Bradford pear profile covers it in detail.

Crabapples share the white spring flowers and small red fruit. Their fruit can be anywhere from 1/4 inch to 2 inches across, and many cultivars open pink or red. A tree with clusters of 1/4-inch red fruit and stiff 1-inch thorns is far more likely a hawthorn.

Seasons and where to look

• Spring: leaves first (common hawthorn is often one of the first trees in leaf), then flowers. In the eastern US most hawthorns bloom in late spring; Maryland's green hawthorn flowers in April. In Britain, Midland hawthorn blooms from mid-April and common hawthorn in May.
• Summer: haws form green, ripening through late summer.
• Fall: haws turn red; Washington and green hawthorn leaves turn red to scarlet, downy hawthorn's yellow-brown.
• Winter: red fruit on bare, thorny branches, red buds, and on 'Winter King', orange patches in gray bark.

The Woodland Trust says common hawthorn flowers and fruits best in full sun, which is why the most heavily flowered trees stand alone or on the sunny side of a hedge. In the US, downy hawthorn grows in a variety of habitats across the Midwest (Morton), and planted cultivars such as 'Winter King' turn up as street trees far from their native range, so a range map alone can't settle which species you have. If you want to come back to a particular tree when its haws ripen, Tree Identifier's Tree Map pins each located identification.