There are several factors to take into consideration when planting bonsai seedlings, with temperature, time of year and seed quality being chief among them. When growing bonsai seedlings it is important to try to replicate the natural environment of each particular species. This is because the seeds are conditioned to sprout in their native areas where the temperature and weather conditions are most favorable to their successful germination. Seeds that are local to a grower's particular area should be ideal for planting and maximum growth. Bonsai seedlings are no different to seeds that are used to grow regular sized trees; it is the method of pruning and cultivation that sets the mature trees apart.
Growing bonsai trees from seedlings can be a long and involved process. The bonsai seedlings can take many months to produce sprouts, with some varieties of trees taking even longer. Many seedlings are notoriously delicate and require different temperatures and conditions to thrive. The fall season is usually the best time to plant the seedlings as they will have had time to sit in the cold winter ground and then be slowly warmed and softened by the spring temperatures. This natural process helps to crack open the seed and jump-start early growth.
An artificial process known as cold stratification can be used if growing the bonsai seedlings indoors and out of season. This requires soaking the seeds in water for a period of 24 hours. The seedlings are then wrapped in a damp paper towel, sealed in a plastic bag and placed into a refrigerator for one week to begin the germination process.
The bottom of a seed tray is layered with small pebbles or gravel for drainage, and then the tray is filled with soil. A thin utensil is used to create furrows in the soil and the seeds are placed, or sown, into the furrows. The bonsai seedlings are then covered with soil and carefully watered with a misting device.
The tray is placed in dappled sunlight, with growers periodically checking to see that the soil is kept moist. Whether the seeds are germinated indoors or outside, after a period of time a few fledgling leaves should begin to appear. At this point the smaller, weaker sprouts are removed to allow the strongest amongst them to grow as a singular sprout. After the mature leaves begin to appear, the saplings are transplanted into separate pots. They are then planted into progressively larger pots, or in the ground, as they continue to grow.