The cold stratification approach produces very high germination rates in these species.1.Fill a plastic bag with growing material. Place a handful of peat moss, vermiculite, or germination paper in a small, plastic, zip-locked bag. For best results, use sterile material and handle it with disposable gloves to avoid introducing fungus.- Tiny "snack-sized" bags work best. Larger bags trap more air with the seeds, which can lead to fungal problems.
- Red maple seeds are sensitive to acidity.For this species, choose vermiculite (a neutral or basic substance) rather than peat moss (acidic).
2.Add a little water. Add a couple drops of water to the growing material to dampen the material slightly. If you see standing water, or if you can squeeze out water from the material, it is too wet.
3.Apply a little fungicide (optional). Fungicide can prevent mold from destroying your seeds, but it is not always necessary, and may damage the plant if overused. Add only in tiny quantities, following manufacturer's instructions.
- Some growers rinse the seeds in very diluted bleach solutions instead.
4.Add the seeds and close the bag. Place your seeds in the bag. Starting from the base, roll the bag to expel most of the air. Zip it closed.
5.Store in the refrigerator . Now it's time to "stratify" the seeds, or expose them to temperatures that trigger germination. For most species, the ideal temperature is usually around 1–5ºC (33.8–41ºF).The crisper drawer of a refrigerator is usually about this temperature.
- Ideally, use a thermometer to confirm the correct temperature. Some seeds may fail to germinate if the temperature is just a couple degrees off.
6.Leave them for 40–120 days, checking every week or 2. Most of these species take 90–120 days to germinate, check on the bag and make adjustments as needed:
- If you notice condensation, pick up the bag and gently tap it to knock the water droplets off. Lay the bag back down on the opposite side, so the wet seeds have a chance to dry off.
- If the growing material has dried out, add a drop or 2 of water.
- If you notice any mold or black spots, remove the affected seed and throw it away. (If the whole batch is molding, try a little fungicide.)
- If the seeds have begun to sprout, remove them from the refrigerator.
7. Plant the seeds. Once the seeds have germinated, plant them 0.6–1.2cm (¼–½ inch) under moist soil. Most do well in partial shade, but look up the exact species if possible for more info on planting.
- To increase the odds of survival, start the seedlings in an indoor seed tray instead. Fill the tray with 7.6–10 cm (3–4 inches) of well-draining potting soil, or an even mix of peat moss, rotted compost, vermiculite, and coarse sand. Water whenever the soil becomes completely dry. Transfer to planter pots once the second set of leaves appear.