Conkers are funny little seeds. Shed from the horse chestnut in the fall, they litter yards and streets. When clearing them from your yard to save your bare feet, collect a few and set them aside for planting. Horse chestnut trees are easy to start from conkers. Simply plant them in the fall and wait for nature to take over in spring. To avoid disappointment after a long winter wait, plant twice as many as you think you will need. A few out of the harvest are bound to be inviable.
Place a roughly 1/4-inch layer of broken pottery shards or gravel in the bottom of the pot to encourage drainage.
Fill the pot to within 1/4 inch of its lip with moistened potting soil.
Remove the spiked casing of the conker to reveal the seed within. Observe the seed for any holes or other signs of damage or disease. Do not plant compromised conkers.
Plant the seed 2 inches deep in the center of the pot.
Water the seed until water drains from the holes in the bottom of the pot.
Place the pot in a shaded spot outdoors.
Water the soil only when it is dry to the touch (stick your finger into the soil to check).
Move the seedling into direct sunlight once it has developed two leaves.
Transplant the horse chestnut to a permanent location the following spring.