Ohio and yellow buckeyes
Ohio buckeye is the smaller of the two and ranges in height from 20 to 40 feet. The palm-like compound leaves carry five leaflets reaching an impressive 6 inches long. A wonderfully dense canopy results from these large, dark-green leaves. The deep shade created below is an excellent retreat from the heat of the day for man or wildlife.
Ohio buckeye is easy to identify in early spring because it is one of the first trees to leaf out. In the fall it can have spectacular yellow color but it is generally the first to concede to an extremely hot and dry summer, dropping its leaves as early as late August. This characteristic alone limits its popularity for use in the urban landscape environment.
The flowers are a pretty, greenish-yellow, or as I like to describe them, not quite white. They emerge in early May just as the leaves have finished unfolding and are 6-7 inches long and about 3 inches wide at the base, tapering to the tip. It is very intriguing to walk upon a buckeye as the flowers begin to open, rising slightly above the foliage-you are definitely compelled to get a closer look.
Yellow buckeye, also found throughout Kentucky, is quite similar to the Ohio buckeye but is larger, reaching heights of 60 to 75 feet. The flowers emerge at the same time and are roughly the same color, but the seed capsule formed after flowering is smooth while the seed capsule of Ohio buckeye is slightly prickly.

Horse chestnuts
While most buckeyes are too large or too messy for a small yard, we occasionally see them on large estates, parks, and in botanical gardens or an arboretum. More frequently in cultivation you will see the European horse chestnut, Aesculus hippocastanum, or red horse chestnut, Aesculus x carnea. The foliage tends to be cleaner and holds on longer. The leaves, also palm-like and compound, carry seven leaflets.
The flowers are what makes the horse chestnuts more desirable. Much larger in size and much showier, the flowers of European horse chestnut start out yellow and turn red and are an incredible 12 inches long. The red horse chestnut's flowers are a rosy red and up to 8 inches long. The fruit capsule is very prickly and typically bears two seeds, while most buckeyes bear only one seed per capsule.

Bottlebrush buckeye
My favorite buckeye has to be bottlebrush buckeye, Aesculus parviflora. While this buckeye is not native to Kentucky it is more suitable to the urban landscape. This large, sometimes-suckering shrub grows to about 12 feet tall and 12 to 15 feet wide. What makes this plant great is that it will grow in sun or shade. It tends to sucker less in a sunny site. It is also more tolerant of dry soils and more disease-resistant than most buckeyes, holding onto its foliage later in the season, giving you great yellow color each fall.
The flowers are white and rise above the foliage, making an absolutely stunning show. They are also long, as with most buckeyes, but are slender from base to tip resembling a bottle scrub brush. The flowers form and begin to elongate in late May, reaching peak color about June 15.

Least poisonous buckeye
In our area bottlebrush buckeye blooms beautifully but rarely sets fruit, which is consistent throughout the north. In most cases only 2 or 3 capsules are formed per mature plant. It can be disappointing, but in many cases this serves as an advantage in the urban landscape since all buckeyes are poisonous. The poor fruit set allows us to plant bottlebrush buckeye in areas where other buckeyes would be too dangerous, such as schoolyards, around a farmhouse, or even in our own back yards.
The beauty and the danger of the buckeye remind us to choose our plants wisely. We often make quick decisions and are lured to purchase a plant without having all the facts. I encourage you to take the time for a little research, consult a professional, or stop by your local library and get to know the plants you fall in love with, before choosing to plant them in your garden.