Do not pack or fill the soil so that it forms what gardeners call “waterproof hardpans.”
To hold the tree in place, you can add twigs, covering soil, etc. The chief base soil should not be sandier than the added soil however. The additives will assist in growing a healthier tree with outward roots and attractive side root shapes. Once you reach this stage, you may want to consider transporting. Be careful since some bonsai will suffer transport shock. You can grow the plants in beds or pots. Growing the plants in beds is ideal, since you will not need to water the plants as often, as well the trunk will thicken as it grows rapidly.
Now you are ready to shape your seedlings once you get past the basics. For now, however we can learn how to propagate the Japanese White Pine.