Red-flowering trees bring a dramatic touch to gardens and landscapes. Their bright blossoms harmonise with orange- and yellow-blooming plants, while contrasting with cooler purple or blue blooms and green foliage. Many trees, including maples, crabapples and elms, produce red blooms. Sumac plants have eye-catching, conical red berry clusters. None of them, however, compare in showiness to the red conelike blooms of Aesculus x carnea, the red horsechestnut tree.
The first documented red horsechestnut appeared in Germany in 1812 as the hybrid offspring of scarlet buckeye (A. pavia) and European horse chestnut (A. hippocastrum). Scarlet buckeye, also called firecracker plant for the brilliance of its blooms, grows from 10 to 40 feet high. Its 6- to 10-inch, erect clusters of tubular blooms open above glossy, dark-green compound leaves in spring. The flowers entice hummingbirds and bees. European horsechestnut, from the mountains of Greece and Albania, typically stands 50 to 75 feet high. Its deeply veined, compound leaves, emerging pale green, darken as they age. Up-to-12-inch clusters of red-and-yellow-blotched, white spring blooms appear on its branch ends in mid-spring.
Red horsechestnut trees typically stand 30 to 40 feet high, with rounded crowns and a 25- to-30-foot spread. Like their parents, the trees have compound, pinnate green leaves. Red horsechestnuts' measure between 6 and 10 inches, with five to seven oblong, serrated leaflets. The foliage retains its lustrous dark-green hue well into autumn before browning and dropping. The trees' greyish-brown bark separates into plates as it ages. Upright, conical red flower clusters from 6 to 8 inches high adorn the ends of the trees' branches in midspring. They give way to prickly, 1 1/2-inch seed capsules containing glossy, squirrel-attracting brown nuts.
Red horsechestnut trees tolerate winter temperatures between --6.67 degrees C and -6.67 degrees C in U.S. Department of Agriculture Plant Hardiness Zones 5 through 8. Their heat tolerance extends to American Horticultural Society Plant Heat Zone 6 through 8, where annual days above 86F number between 45 and 120. The trees flourish in full sun to partial shade and moist, rich soils. They may suffer leaf scorch in extended drought.
Red horsechestnut cultivar "Briotti," introduced in 1859, stands 25 to 35 feet high and wide. Sometimes called ruby horsechestnut, it boasts larger flower clusters of a richer red than other varieties. Aesculus x carnea "Fort McNair," at 35 to 50 feet high with an up-to-40-foot spread, produces rose-red flower clusters in late spring and early summer.
While red horsechestnut's disease resistance surpasses that of both its parents, the tree may experience cracking bark with excessive sun exposure. Its fallen flowers and leaves can be messy. Its branches droop with age. Trees planted where vehicles or passersby pass beneath them require removal of their branches for clearance.