Many different species of maple trees (Acer sp.) exist, all of which can be grown from seed. Maple fruits or nuts, also called samaras, ripen and drop to the ground in fall, except for red and silver maples, which mature and drop in late spring or early summer. The red maple (A. rubrum) and silver maple (A. saccharinum) need no pretreatment and can be planted directly into the ground immediately after harvesting the seed. For the other maple tree varieties, some pretreatment is necessary in order to coax the seeds into germinating. For all maples, you can plant the entire “fruit” instead of extracting the seed first.
Stratify (provide a cold treatment to) the maple tree seeds in the fall. Fill a plastic sandwich bag with a handful of damp peat moss or vermiculite and place the seeds in the bag. Store the seeds in a refrigerator at 33 to 41 degrees Fahrenheit for about 90 days.
Fill a seed tray with a 3- to 4-inch layer of rich but well-draining potting mix. You can also use a mixture of equal parts peat moss, organic compost, vermiculite and coarse sand.
Plant the maple tree seeds a quarter-inch to 1-inch deep in the potting mixture, spaced about 1 or 2 inches apart. Plant the stratified seeds in late winter or early spring.
Water the potting mix to keep the seeds evenly moistened, but allow the water to drain thoroughly. Let the potting mix dry out completely between waterings.
Set the seed tray in partial sunlight (about 50 percent) when the seeds begin to germinate. Keep the seed tray at room temperature while germinating and sprouting the maple tree seeds.
Transplant the strongest maple tree seedlings outdoors or into individual planter pots after they’ve developed their second set of leaves, or “true leaves.”