So you want to try to grow the magnificent Southern Magnolia from a seed? It's not to difficult a process, but there are pros and cons.
You can propagate Southern Magnolia by seed, cuttings taken in the summer, or from grafting. The drawback growing them from seed is that the trees might take 15 or more years to bloom. Cutting grown plants are superior to most seedlings because they begin flowering the first year or two after propagation. But, then, there's a drawback to rooting magnolias: it's not easily done. Even with misting systems and rooting hormones, the percentage of successfully rooted cuttings is often very low and best left to the professional/ commercial growers.
Growing Magnolia From Seed
Collect the seeds as soon as possible after the fruit is mature. Depending on the weather, and your location, this is usually sometime from mid-September through early October. Spread the cone-like fruits on a table and allow them to dry for several days. When the fruit has opened shake it and the seeds should fall right out.
You can either plant the seed now - if you have a greenhouse or indoor growing environment - or you can wait until spring to plant them, which is what I recommend.
Whether you plant the seed now or in spring, the seed should be cleaned before planting or stratifying (storing). To remove the fleshy seed coat, soak the seed overnight in warm water. Rub the seeds against hardware cloth or window screening to remove the fleshy coat. After cleaning, the seeds should be sown immediately or stored for 3 to 6 months at about 40 degrees F and planted in the spring. Note: Seeds stored over winter at room temperature seed will lose its viability.
An excellent way to stratify (store) seeds is to use a polyethylene bag and place alternating layers of a moist medium such as a sand and peat mixture and seeds in the bag. Tie the top of the bag and place in a refrigerator at about 40 degrees. The medium should be just moist enough to stick together but not so wet that it will drip if squeezed by hand.
Planting the Seeds
Whether sown in the fall or in the spring, the seeds should be planted in seedbeds or small containers (3 to 4" pots). Cover the seed with about l/4" of soil and then mulch to prevent drying. The soil in seedbeds or small pots should be kept moist until germination is complete. Then keep soil damp.
Grow the seedlings in a partially shaded environment during the first summer. Morning sun with afternoon shade would be perfect.
When a good amount of roots have developed, or have filled the soil in the small pot, you can transplant the seedling to a larger container (6" or 1 gallon). When the roots have filled out in the larger container the trees can be transplanted to landscape beds.