I've been impressed with the buckeyes blooming on campus this spring. These trees seem to have been unaffected by our late spring frosts or recent downpours.
Buckeyes (also known as horsechestnuts) are members of the genus Aesculus. They all have palmate leaves meaning they have about 5 leaflets that fan out like fingers on your palm. They have showy flowers in spring, which mature to large dark brown capsules by 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 used most often as landscape trees. All are coarse looking in winter with stout, barren twigs and branches. Most insist on sunny sun sites with moist, fertile, well-drained soils. All abhor poorly drained soils.
Below are descriptions of a few of the species planted at the Iowa State University campus in Ames. You might consider some of these for sites in your landscapes.
Ohio Buckeye (Aesculus glabra) has greenish yellow flowers in mid May on trees that may reach 40 foot 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. The capsules are housed in husks covered with small spines. You don't have to be from that other state college in Ohio to root for this buckeye!
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 centers. 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 at maturity.
For more vibrant flowers, the Red Horsechestnut (Aesculus xcarnea) 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.
There are several hybrid buckeyes; most notably 'Autumn Splendor'. The leaves of Autumn Splendor Buckeye have little summer leaf scorch and brilliant maroon-red fall color. The flowers are cream colored on trees that ultimately reach 30-40 feet tall.
The Red Buckeye (Aesculus pavia) is another red flowering buckeye. It is one of the parents in the Aesculus xcarnea 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 and generally look poor on campus by mid to late summer (especially in soils that are dry). In addition, Red Buckeye is not commonly available in nurseries and garden centers in the Midwest.
One of my favorite buckeyes is the Bottlebrush Buckeye (Aesculus parviflora). Bottlebrush Buckeye is also the oddball of the buckeye bunch. It is the smallest; reaching only 8-12 feet tall. Because of its diminutive size, it is often used as a shrub in the landscape. It has showy, white, 12-inch long flowers in summer (usually July) 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.
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