Tree seeds come in many shapes and sizes. Left alone in the wild, some tree seeds can take years to germinate. Most tree seeds are dormant when they reach maturity, and they need certain conditions to break their dormancy. Tree seeds are more likely to grow successfully if you germinate them before planting them in the garden, to keep them protected from animals, insects and disease. The process of germinating the seeds also tells you if they are viable so you do not waste precious garden space waiting to see if they will grow.
Scarify your tree seeds if they are very thick. Thick, hard shells like those on cherry or plum seeds need to be scarified to help them open up for germination. Scarify the seed by gently rubbing it with a file or sandpaper, or by nicking it with a knife. Take care not to damage the soft, white embryo inside.
Soak the seeds in room temperature water for 24 to 48 hours. Soaking softens the shells and lets some moisture reach the embryo, to help it break its dormancy. Soaking also helps you see if any seeds are dead because viable seeds usually sink to the bottom and dead seeds float.
Plant directly into the ground the seeds that do not need any treatment before they germinate. Seeds vary greatly in their germination requirements. For example, seeds from some maple tree varieties can be planted soon after they have matured and dropped to the ground.
Stratify seeds that need temperature changes to break their dormancy. You can artificially stratify seeds in the refrigerator or stratify them naturally in pots outdoors, during the cold season. Fill the pots with dampened, sterile peat moss. Cover the seeds with the moss and set the pots outside in the sun where they will not be disturbed by strong winds. Keep the peat moist. Leave the seeds until late spring, when the soil has started to warm. Outdoor stratification may not be effective for seeds that are not native to your region if the winter temperatures are too cold or too warm for them.
Use the same sterile peat moss to artificially stratify tree seeds. Soak the peat moss with water and wring it out until it is moist and not drippy. Place the seeds and the peat into a resealable plastic bag and mix them around so all of the seeds are touching the wet peat. Seal the bag and place it in the crisper drawer of the refrigerator for one to four months, according to the seeds' requirements.
Check naturally and artificially stratified seeds for signs of rot, mold or other damage just before you plant them. In general, seeds that feel hollow or squishy, or seeds that are covered with mold are not viable and can be thrown away.
Plant the seeds in earth-filled pots or directly into the ground. Tree seeds should be planted at a depth that is twice the length of the seeds. Make sure the seedlings stay in partial shade for the first year or two, and ensure that their soil stays moist and not too wet.