Bonsai is the practice of growing miniature trees in containers and carefully controlling their size and shape through pruning. There is no such thing as a bonsai species of tree; instead there are more than 250 varieties of trees that are cultivated and groomed in the art of bonsai. Planting seeds for development as bonsai trees is not difficult, but the right container and growing conditions are important. This information is provided to help propagate seeds for your bonsai tree through forced germination, indoors at any time of year.
Place the seeds in a bowl of water and soak for between five and six hours. Seeds that sink to the bottom of the bowl are viable for germination; seeds that float are empty shells and should be discarded.
Wet the inside of a plastic bag to dampen it, and place the seeds inside the bag. Leave the bag at room temperature for three to four days.
Place the bag on the bottom shelf of your refrigerator. Over a two-week period, gradually move the seeds up the shelves of the fridge, one shelf at a time. Let the bag rest on the top shelf for two to three days, and then gradually move it successively down the shelves over another two-week period. This process is called cold stratification. There are certain species of trees that require heat stratification in the midst of the cold stratification process. Check with your local nursery to determine if your seeds are in this category. If so, remove the bag from the fridge after the first two-week period, place the seeds in a bowl and let them sit at room temperature for two to three days. Put them back in the bag and refrigerate them for another two weeks, beginning at the top shelf and successively working them down the shelves.
Sow the tree seeds for your bonsai tree into a small pot filled 1/2 to 2/3 full of fast-draining seed compost. Tamp the soil lightly. Spread the seeds on top of the soil and cover them with a layer of the seed compost, not more than 1/2-inch thick. Add a thin layer of sand over the compost to keep the seeds in place.
Keep the seeds moist but not soaking, at all times. Place the seed pot in a windowsill that receives indirect sunlight for most of the day. Depending on the tree species you planted, the seeds may take from two to four weeks to germinate.
Plant the seedlings into individual pots, once they have at least two true leaves. Plant the seedlings in the same type of seed compost that you used to help them germinate. Fertilize the seedlings gently for six weeks after you replant them. As the seedlings thrive, replant them into the container where you will train them to become bonsai.