Fill a growing tray with 2 inches of perlite, peat moss or other planting medium. The medium must be able to hold water but also drain well.
Sow the sycamore seeds in the tray 2 inches away from each other. Plant them in a furrow 3/4 inch deep.
Place the tray where it will receive direct sunlight for several hours a day. The seeds will not germinate in full shade.
Mist the tray regularly. You want the planting medium to remain damp but not wet.
Regulate the tray's temperature. If it falls below 59 degrees Fahrenheit, warm it by giving it more sunlight. If it rises above 86 degrees, remove it from direct sunlight.
Continue tending the seeds. Within two to three weeks, they will sprout. The first leaves will look round and immature. As soon as the first true leaves appear, the seedlings are ready for transplant.