How to Propagate Horse Chestnut Trees
In general, horse chestnut propagation is not the simplest task. However, it can be accomplished. The process of propagating horse chestnuts can be done by seed (through conkers) or you can choose to propagate horse chestnut trees through cuttings.
Propagating Horse Chestnut Conkers
To begin the process of growing new horse chestnuts by seed, growers need to collect the conkers. To collect the seeds, it is best to wait until they have naturally fallen from the tree. This will help ensure that the seeds are fully mature and viable. Always choose seeds that show no cracks, holes, or other signs of insect damage. Like many tree seeds, horse chestnut propagation requires both time and patience. When handling horse chestnut seeds, always make certain to wear gloves and limit exposure, as the seed contains several toxins that may irritate skin. Remove the seed from the outer spiny husk and place into a vented plastic bag filled with moist peat moss. The bag will require at least a three month period of cold stratification. This stratification can occur by placing the bag into an old refrigerator. Label the bag clearly with its contents and the date. Make certain to keep the bag out of reach of children, pets, or anyone else who may disturb it. Remove the horse chestnuts from the cold treatment, and plant them indoors in deep containers with excellent drainage, as horse chestnuts are prone to rot when conditions are too wet. Plant the conkers at least two times as deep as their height. Place the newly potted seeds in a warm and sunny window.
Growing New Horse Chestnuts with Cuttings
Propagating horse chestnuts can also be achieved through softwood and hardwood cuttings. Cuttings of horse chestnut can be taken in spring, for softwood, or during fall for hardwood cuttings. These cuttings should be 4-6 inches (10-15 cm.) long and placed into well-draining soil media. You may dip the cut ends in rooting hormone for better results. Place softwood cuttings out of direct sun and keep the soil consistently moist but not too wet. Hardwood cuttings will need to be kept in a location that won’t freeze over winter, like the garage or even a greenhouse, until spring planting. You can also place them in the refrigerator. These, too, must be kept moist. Allow the seedlings or cuttings to become established, and plant out into the garden as soon as all chance of frost has passed in the spring. Make certain to harden off the seedlings before transplanting to ensure the greatest chance of success.
