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By Alan Branhagen, Arboretum Director of Operations
Put a couple of buckeyes in your pocket, luggage or car and you shall have good luck and safe travels – so goes the myth at least! In late summer into early fall, buckeye trees’ fruits ripen: the husks split and out pops a rich brown, almost polished looking dark brown nut with a light tan eye – the buckeye! The nuts are often first spied on the ground with a “where did that come from?” glance upward.
Buckeyes and their Old World relatives known as horsechestnuts (the nuts known as conkers in England) are shrubs to shade trees found widely across the Northern Hemisphere. They comprise the Genus Aesculus and the Arboretum has a lovely collection of these on Three-Mile Drive just past – and downhill from – the maze garden on the left side. They are loved as ornamental trees the world over for their showy late spring blooms. The white-flowering Common Horsechestnut (Aesculus hippocastanum) is widely planted as a street tree across Europe and wherever hardy, although it originated in the wild from a small area in high elevations of the Balkan Peninsula.
North America’s most famous member is the Ohio Buckeye (Aesculus glabra) which is its namesakes state tree. It is usually an understory tree but can become quite large and over 50 feet tall over time. It is common in the lower midwest and surprisingly hardy across the entire upper midwest. It has greenish-yellow flowers rich in nectar for pollinating insects and hummingbirds and these produce the classic buckeyes described prior.
Buckeyes and horsechestnuts are often the first trees to leaf out, with stunning palmately compound leaves (the leaflets arranged like fingers on a hand). One drawback is they can also be the first tree to drop their leaves in late summer. The Arboretum selected the hybrid cultivar Autumn Splendor for the reason that is often holds its foliage well and then turns a rich fall color.
Bottlebrush Buckeye (Aesculus parviflora) is a huge shrub species of buckeye native to the state of Alabama and barely into adjacent areas. This shrub has towering spikes of white flowers in mid-summer and puts on quite a show like the fireworks of the season. It was considered marginally hardy but shrubs at the Arb have thrived for decades now without dieback as the winters have moderated. Be sure and plan for a lot of room for this shrub as it also suckers to form a thicket over time.
Horsechestnuts are tenderer at the Arboretum and show past signs of winter injury in the form of bark splitting. The Arb’s collection includes the Common Horsechestnut, its double flowering cultivar ‘Baumannii’ and the Japanese Horsechestnut (Aesculus turbinata) which might be a bit showier tree with white flowers and good orange fall color.
Red Buckeye (A. pavia) with brilliant red flowers pollinated by hummingbirds is native to the American Southeast and not proved hardy whatsoever at the Arb. Hybrids with this species and the buckeyes and horsechestnuts have proven hardier and the Arb is trying to backcross some of these to get even richer red flowers. Hybrids of Red Buckeye and Common Horsechestnut (Aesculus x carnea) have pink flowers and a cultivar from Nebraska ‘Fort McNair’ is doing quite well, destined to be a more popular pink-flowering tree for gardens.
Buckeye and Horsechestnut nuts are not edible to humans but squirrels devour them just fine and plant them all around – buckeye trees readily naturalize because of this, but we do not see any horsechestnut seedlings.