Horse chestnuts are large trees that provide lovely shade and interesting fruits. They are hardy to USDA zones 3 to 8 and are normally used as landscape trees. Their prolific fruit litter results in hundreds of intriguing nuts that can be container grown into trees. However, a potted horse chestnut is a short-term solution, as the plant will be happiest in the ground unless used as a bonsai.
Can You Grow Horse Chestnuts in Pots?
You can start horse chestnut trees in containers and plant them out when the trees are two to three years old. By that point, you would need a super huge pot to continue to grow the tree or it will need to get in the ground. Since the tree develops into a 30 to 40 foot (9-12 m.) specimen, container grown horse chestnut plants will eventually need to be moved to a well-prepared site in the landscape. However, they are fairly easy to turn into bonsais with a little know how.
If you want to try growing one of these stately trees, collect healthy, firm nuts from the ground in fall. Use good potting soil and cover the seed, removed from the husk, in enough soil to cover it to twice its length. Moisten soil and keep it damp, placing the container in a cool site such as a protected area outdoors, an unheated greenhouse, or cold frame.
Cover the container with plastic film or glass to conserve moisture and direct heat into the soil. It is fine if the container experiences cold. Like many seeds, horse chestnut plants need a period of chilling to release embryonic dormancy. Mist the container when it feels dry.
Caring for a Young Potted Horse Chestnut
Your container grown horse chestnut will produce two little cotyledons in spring and eventually some true leaves. Remove the plastic or glass as soon as you see these. Soon the plant will develop several true leaves. At this point, move the plant to a larger container, taking care not to damage the delicate, new root structure.
Keep the plant outside in a sheltered location and give average water. After a year of growth, the following spring, the tree can be moved into the garden or start training as a bonsai. Keep weeds away from an in-ground little tree and mulch around the root zone. Once it establishes, it will need little attention.
Bonsai Training for Horse Chestnut Trees in Containers
If you want to keep horse chestnut trees in planters, you will need to root prune. In spring, nip off the leaves and allow just three pairs to sprout and persist. Keep pruning off other leaves that sprout until summer. Let any further leaves remain.
The next year, repot the plant. Once removed from soil, prune two-thirds of the taproot. After four years, the tree is ready to be wired to develop an interesting form.
Every few years, repot the tree and prune the roots. Over time, you will have a little horse chestnut tree that will happily grow in its container with continued pruning, wire training, and root care.