These trees sport long, showy, typically upright clusters of flowers atop their branches in springtime. Some develop good fall color. Leathery capsules release glossy, dark brown, chestnutlike seeds (buckeyes) in autumn. Prune established horsechestnuts only to remove dead branches. Summer leaf scorch is common when the plants are grown in poor, dry soil; severe cases result in defoliation.
A. x arnoldiana 'Autumn Splendor'. Zones US, MS, LS; USDA 6-8. Very attractive, hybrid of A. flava, A. pavia, and A. glabra. To 3540 ft. tall and nearly as wide. Glossy, dark green leaves with five (rarely seven) leaflets turn brilliant maroon in autumn and are resistant to leaf scorch. Yellow flowers, each with an orange-red blotch, are borne in clusters to 8 in. long. Best with some shade.
A. x carnea. RED HORSE-CHESTNUT. Zones US, MS, LS; USDA 6-8. Hybrid between A. hippocastanum and A. pavia. To 40 ft. high and 30 ft. widesmaller than A. hippocastanum, better fit for small gardens. Round headed with large, dark green leaves, each divided into five leaflets; casts dense shade. Bears hundreds of 8-in.-long plumes of soft pink to red flowers. 'Briotii' has rosy crimson flowers; 'Fort McNair' blooms rose-pink, and 'O'Neil's Red' has bright red blooms.
A. flava (A. octandra). YELLOW BUCKEYE, SWEET BUCKEYE. Zones US, MS, LS; USDA 6-8. Native to the American South. Most majestic of the North American native species: handsome, round-crowned tree to 90 ft. tall and 50 ft. wide, with dark green leaves divided into five to seven finely toothed, 5- to 8-in.-long leaflets. Yellow flowers form on erect panicles; less showy than those of A. hippocastanum. Smooth, brown bark. Orange fall foliage.
A. glabra. OHIO BUCKEYE. Zones US, MS; USDA 6-7. From the central and eastern U.S. Low-branching tree with dense, rounded form; to 40 ft. or possibly taller, to 30 ft. wide. Early to leaf out. Foliage is bright green when new, matures to dark green, turns yellow to orange in fall. Greenish yellow flowers in 4- to 7-in. clusters. Prickly seed capsules enclose shiny brown buckeyes.
A. g. arguta (A. arguta). TEXAS BUCKEYE. Zones US, MS, LS; USDA 6-8. Native to southern U.S. Attractive small tree to 1520 ft. or taller, 1215 ft. wide. Leaves divided into seven to nine narrow, pointed, 3- to 5-in.-long leaflets. Pale yellow flowers in late spring. Weight of fruit may bend branches in fall.
A. hippocastanum. COMMON HORSECHESTNUT. Zones US, MS; USDA 6-7. Native to Europe. To 60 ft. tall, 40 ft. wide. Bulky and densely foliaged; gives heavy shade. Leaves divided into five to seven toothed, 4- to 10-in.-long leaflets. Spectacular flower show: ivory blooms with pink markings in 1-ft. plumes. Invasive roots can break up sidewalks. 'Baumannii' has double flowers, sets no seed.
A. parviflora. BOTTLEBRUSH BUCKEYE. Zones US, MS, LS, CS: USDA 6-9. Native to southeastern U.S. Shrub to 1215 ft. tall and wide, spreading by suckers, with dark green leaves divided into five to seven 3- to 8-in.-long leaflets. Very showy white flower clusters (812 in. tall, 24 in. wide). Bright yellow fall foliage. Good choice for massing, shrub borders, or specimen or understory planting. A. p. serotina 'Rogers' has 112- to 212-ft.-long flower clusters that are drooping rather than upright and appear about 3 weeks later than those of the species.
A. pavia. RED BUCKEYE. Zones US, MS, LS, CS; USDA 6-9. Native to eastern U.S. Understory shrub or tree grows to 1220 ft. tall and as wide, with irregular rounded crown. Glossy deep green leaves with five to seven 3- to 6-in.-long leaflets. Bears narrow, erect 10-in. clusters of bright red or orange-red (rarely yellow) flowers. Does best in light shade. Good choice for warm, humid climates.