Conker trees, also referred to as horse chestnut trees, grow easily from seeds when planted in appropriate soil and watered as necessary. Plant the seed in the fall before the first frost to see it sprout the following spring.
Conker trees grow best in Zones 3 through 8 as defined by the United States Department of Agriculture. Those zones cover almost the entire continental United States. Plant the tree in an area that receives at least 8 hours of full sun, covering the seed by about 2 inches of soil.
In areas with poor soil, add fertilizer to provide additional nutrients for the plant. Water regularly to prevent the soil from drying out, but ensure that the water drains properly to avoid root rot, which kills the seed or sapling. In colder climates, cover the sapling over the winter to protect it from damaging frost. During the growing season, surround the sapling with a 4-inch radius of mulch to protect the roots and prevent disturbance from weeds.
As the tree grows, watch for signs of distress such as leaf blotches and discolorations. Conker trees are susceptible to some bacteria and pests, some of which can kill the tree if not addressed.