Aesculus

Bottlebrush buckeye (Aesculus parviflora) is a big, suckering, mound-forming deciduous shrub from the rich woodlands of the Deep South, native to Alabama and southwestern Georgia. It is grown for three things: bold, palmately compound leaves that cast deep summer shade; tall, erect white flower panicles, 8 to 12 inches long, that stand up like bottle brushes above the foliage in mid summer when little else blooms in shade; and a clean golden-yellow fall colour. The flowers, white petals set off by pink-red anthers, draw bees and butterflies and are visited by hummingbirds. Its greatest asset and its main catch are the same trait: it suckers steadily from the roots into a broad, dense colony 8 to 15 feet across, so this is a shrub for space, not for a tight foundation bed. It wants part to full shade and moist, rich, well-drained soil, and it resents drought, especially when young. Note that the smooth brown seeds (buckeyes) and the other parts are poisonous if eaten.

A large, stately deciduous shade tree from the Balkan mountains of southeastern Europe, long planted across cool-temperate parks, avenues, and large lawns for its dramatic spring bloom and dense summer shade. In May it covers itself in upright, candle-like panicles of white flowers blotched yellow then pink, carried above big, coarse, palmately compound leaves of five to seven leaflets. By autumn it drops spiny green husks that split to release glossy mahogany-brown seeds - the 'conkers' of British schoolyard tradition. It is grand but high-maintenance and strictly ornamental: all parts, and especially those tempting shiny seeds, are toxic to people and livestock, and the tree is plagued by leaf blotch and the horse-chestnut leaf miner that brown the foliage by late summer. Do not confuse it with the unrelated, edible sweet chestnut (Castanea sativa) - that name overlap is a genuine and dangerous source of poisonings.

Red buckeye (Aesculus pavia) is a small understory tree or large shrub of the moist woods, bottomlands, and bluff bases of the southeastern and south-central US, grown above all for its spring flowers. It is among the first woody plants to leaf out, and in April and May it hangs the new palmate foliage with showy, erect panicles, 4 to 10 inches long, of narrow, tubular, red to orange-red flowers. Those tubes are built for hummingbirds: in much of its range the bloom is timed almost exactly to the return of ruby-throated hummingbirds on spring migration, and bees work the flowers too. It is a modest 12 to 20 feet tall, often multi-stemmed, happiest in the part shade of a woodland edge in moist, well-drained soil. Be honest about its two catches. It is one of the earliest trees to quit for the year, with the leaves declining in mid to late summer and often dropping by the end of September, so it can look bare while everything else is still green; and the smooth brown seeds (buckeyes) and other parts are poisonous if eaten.

A garden hybrid (Aesculus hippocastanum x A. pavia) grown for its showy, upright panicles of rose-red to pink flowers in mid-spring, set against bold, dark-green, palmately compound leaves. It makes a tidy 30-40 foot medium shade or specimen tree with a dense, pyramidal-to-rounded crown. Its main selling point over the common horse chestnut is health: red horse chestnut is far less prone to the leaf blotch and leaf scorch that brown out and disfigure A. hippocastanum by late summer, so the canopy holds up better through the season. The flowers draw bees and, with their narrow rose-red tubular florets, hummingbirds. One load-bearing caution applies: like all Aesculus, the smooth brown seeds (conkers) and other parts are toxic if eaten, so site it thoughtfully where there are children or pets. It is a low-seed-set hybrid, not weedy or invasive.