Buckeyes and horsechestnuts are members of the genus Aesculus. The true chestnuts are members of a different genus - Castanea. Members of the genus Aesculus have palmate leaves – meaning they have 5-7 leaflets that fan out like fingers on your palm. They have showy flowers in spring, which mature to large dark brown capsules in late summer or early fall. While the hard, shiny buckeye fruits are considered good luck when carried in your pocket, they should not be eaten since they are poisonous to people.
Members of this genus are frequently planted in the landscape. Some are giant trees – reaching 75 feet tall while others are much smaller. All are coarse-looking in winter with stout, barren twigs and branches. Most insist on sunny sites with moist, fertile, well-drained soils. All abhor poorly drained soils.
Below are descriptions of a few of the species grown in Iowa and around the Midwest. You might consider some of these for sites in your landscapes. With this sort of diversity, surely there is a buckeye or horsechestnut that will work in your landscape.
Ohio Buckeye (Aesculus glabra) has greenish-yellow flowers in mid-May on trees that may reach 40 feet tall or more. While the foliage is a beautiful complement to the flowers in spring, the Ohio Buckeye is troubled by foliar diseases in some summers. One notable cultivar is Autumn Splendor. The leaves of Autumn Splendor Buckeye have little summer leaf scorch and turn a brilliant maroon-red color in fall. The capsules are housed singly in husks covered with small spines.
The Yellow Buckeye (Aesculus flava) has yellow flowers in May and smooth capsules covering a pair of buckeyes. The leaves of this buckeye are less troubled by foliar diseases and often display decent orange fall color. But give this one plenty of room in the landscape – it often reaches 75 feet tall.
Common Horsechestnut (Aesculus hippocastanum) has large showy white flowers with yellow and red center markings. The leaves are large (up to 10 inches), coarsely toothed and turn yellowish in fall. The nut is enclosed in a spiny husk. The Common Horsechestnut is also a large tree, often reaching 50-75 feet tall or more at maturity.
For more vibrant flowers, the Red Horsechestnut (Aesculus ×carnea) is a popular landscape tree. The bold rose-red flowers are spectacular in May. The trees are smaller than the other horsechestnuts, usually ranging from 25-40 feet tall, making this beauty more suitable for the typical home landscape.
The Red Buckeye (Aesculus pavia) is another red flowering buckeye. It is one of the parents in the Aesculus x carnea cross. It is typically used as a large shrub or small tree and grows to about 20 feet tall. While the red flowers and foliage are more refined looking than the Red Horsechestnut, the leaves on Red Buckeye scorch by mid to late summer (especially in soils that are dry).
One of my favorite buckeyes is the Bottlebrush Buckeye (Aesculus parviflora). Bottlebrush Buckeye is also the oddball of the buckeye bunch. Unlike the other buckeyes, this one blooms in summer and it is the smallest; reaching only 8-12 feet tall. This makes it a wonderful large shrub in the landscape. It has showy, white, 12-inch long flowers with elongated white stamens that give the flower a "bottle-brush" effect. The leaves are smaller than other buckeyes, dark green, finely toothed, and have no foliar disease problems. Bottlebrush Buckeye will also tolerate light shade considerably better than the other buckeyes and still bloom well. The only drawbacks to this buckeye are that it is slow to establish and is relatively expensive.