Corylus

A rounded, multi-stemmed deciduous shrub native across eastern and central North America, grown for its edible nuts and its season-opening catkins. Showy 2-3 inch yellowish-brown male catkins dangle from bare branches in early spring before the ovate, double-toothed leaves emerge; small egg-shaped edible nuts ripen inside leafy husks by mid- to late summer. Easygoing in average soil and tolerant of clay and black walnut, it suckers into thickets that screen and shelter wildlife.

Common hazel (Corylus avellana), also called cobnut or European filbert, is a multi-stemmed deciduous shrub or small tree of European and western-Asian woodland and hedgerow, growing 12 to 20 feet tall with soft, doubly toothed, rounded leaves. It is one of the great wildlife and working plants of the temperate garden: pale-yellow "lambs-tail" male catkins hang all winter and open in late winter before the leaves, and the edible hazelnuts ripen in autumn. Coppiced on a rotation it yields straight poles and, per the Woodland Trust, opens a wildflower-rich woodland floor. The honest catches: it suckers and can become a thicket if left unmanaged, and in North America it is susceptible to Eastern filbert blight, which is why nut growers there favour resistant hybrids.

Filbert (Corylus maxima) is a large deciduous shrub native to southeastern Europe and southwestern Asia, from the Balkans through to Ordu in Turkey, where it has been cultivated for its larger-than-hazelnut edible fruits for millennia. In the garden it doubles as bold structural foliage - especially the wine-purple cultivar 'Purpurea' - making it as much an ornamental as a productive shrub. The honest catch is its sheer bulk and suckering ambition: left unmanaged it rapidly forms an impenetrable multi-stemmed thicket 20 to 33 feet tall, requires another Corylus nearby for worthwhile nut crops, and squirrels reliably harvest the nuts before the gardener does.