Aesculus parviflora, Bottlebrush Buckeye – 4 (2)

By Catherine Siddall

Michael Dirr’s tome on woody plants is unlikely bedside reading because of its unwieldy size and dry, point-form style. It is a manual, after all. But by skipping to the Landscape Value listing I am often rewarded with an entertaining insight based on Dirr’s experience with these plants over a considerable period of time. (It can take years, even decades, to learn about how woody plants adapt and grow.) I pay particular attention to his evaluation of North American woody natives because I am convinced of their great untapped potential for use in the built landscape.

Aesculus parviflora, bottlebrush buckeye, is featured in glorious golden fall colour on the cover of my paperback copy of Dirr’s Manual of Woody Landscape Plants. The author’s enthusiasm for this plant is evident: “Excellent plant for massing, clumping or placing in shrub borders…even if it didn’t flower it would be a superb shrub for foliage effect”. Under the Flowers heading he continues, “In my mind, it is one of the handsomest of all native southeastern flowering shrubs.” After reading this, I was hooked.

I was excited to discover two mature bottlebrush buckeyes on the way home from my daughter’s school near Ossington and Davenport in Toronto, Ontario. These shrubs were massed with overgrown yews tight against the shady west side of a yellow brick house. Not the most inspiring specimens, but a clear indication that this native of South Carolina and Alabama is hardy and living in difficult conditions up here. (Various sources report Aesculus parviflora as hardy to USDA zone 4.)

When I asked Wendy Woodworth, Horticulturist for the Toronto Museums, about this plant she directed me to one she had planted several years ago in a shady back border at Spadina Historic House. Although I had missed its blooms, I could see that seeds were beginning to form on this buckeye. Consulting Dirr again I read that he had “not noticed abundant fruit set in northern states possibly because of shortness of growing season”. He cautioned that seeds not be allowed to dry out but be planted as soon as they were collected.

There was a good supply of light brown smooth seeds produced by the Spadina plant and I carefully collected a few when they had attained a size between one and two inches. I planted them in containers filled with rich soil and sank the containers into the ground in my rows of perennial divisions next to my compost bins. It was close to the Spadina Gardens Plant Sale in May when I thought of them again, as I helped to haul the perennials out of their holding beds in preparation for the sale. I was excited to see that most of the bottlebrush buckeye seeds had germinated and were sending up new growth. I carefully potted all but one of the seedlings and found new homes for them through the plant sale. The last one has been struggling along under my mature apple tree ever since; it’s now up to 16”.

A few years later, having planted some bottlebrush buckeyes on clients’ properties, I harvested seeds once more and planted them carefully in small pots, again sinking them in the ground. This time none germinated. Even though I put netting all around the pots to protect them from marauding squirrels, my early success germinating these seeds was not to be repeated.

The most magnificent bottlebrush buckeye I know is on a well-treed property north of Toronto in gardens that I maintain. It stands about two metres or seven feet high (bottlebrush buckeyes can get much taller in warmer climates) excluding the foot-long flowering panicles resembling the bottlebrushes that give this shrub its common name. The showy upright spikes are bedecked with small white-petalled flowers whose curving stamens are tipped with dark red anthers. This particular specimen, which is planted in a shrub border under a canopy of mature hemlocks and white pines, flowers gloriously at the same time as trumpet lilies when no other woody plants are blooming. Since I am often too busy working to observe the flowers for long, I have not seen the many species of butterflies and insects that reportedly visit them frequently. The flowers must be successful in attracting pollinators since this plant has little difficulty producing seeds.

Bottlebrush buckeye has lustrous, large, dark green, palmately compound leaves typical of the chestnut family. Unlike the exotic horsechestnut, Aesculus hippocastanum, it appears immune to the many pests and diseases that discolour and ruin the leaves of other plants of this genus. In fall the leaves turn a clear yellow before dropping to reveal the elegant curving branch structure that will grace the winter garden.

This shrub is suitable for even the most difficult growing situation – under the dreaded Norway maple (Acer platanoides). With a little irrigation and occasional top dressings of compost several bottlebrush buckeyes I know are doing well under these common Toronto residential trees. In deep shade they do not produce as many flowers as they would in sun, but the shape, leaves and carefree nature of this plant more than recommend it for difficult situations. I have rarely designed a garden that does not include one.

Some experts suggest that bottlebrush buckeye grows too large for a small garden; they even recommend cutting it to the ground if this becomes a problem. I think that with some allowances for its eventual wide girth (perhaps as much as twice its height), it can happily be sited in many cultivated and naturalized settings. It grows so slowly that it is not likely to exceed its allotted space.

The only problem I have had with this plant is acquiring decent-sized specimens. My limited experience would indicate the bottlebrush buckeye is difficult and slow-growing when starting it from seed. Even when the suckering growth is used to produce new plants – a much faster method – I have found that the resulting plants are often a bit pricey at nurseries. This confirms the investment in time made by growers.

When purchasing Aesculus parviflora check that it was grown in your area to ensure hardiness there. Many marginally hardy and hard-to-source plants are imported from distant nurseries (bottlebrush buckeyes among them). Plants from Carolina may not be hardy in the Toronto region but local stock would.

The addition of a bottlebrush buckeye to your garden or woodland will be a carefree investment that will repay you with many seasons of pleasure.