Many of the bonsai styles we use represent a struggle for the tree's survival in nature. A dramatic example is "root-over-rock". The image is of a stunted tree growing in the scarce soil of rock crevices, with its roots searching in the cracks for what little water and nutrients it can find. Usually the plant chosen is deciduous with small leaves and long, strong roots which thicken relatively quickly. Appropriate plants include Ficus spp., Fuchsia, Oriental Bittersweet (Celastrus orbiculatus), Trident Maple (Acer buergerianum), Carmona microphylla, Kinnikinnick and several varieties of spreading juniper. We are going to use Cotoneaster horizontalis (rock cotoneaster), which has tiny, shiny green, oval leaves. It was a purchased plant from a nursery, in a one-gallon pot, with a large root system for the size of the plant.

Next, we need a rock. This may take some time, if you hope to find one when walking, camping, etc. Searching construction sites can sometimes be successful, as rocks are unearthed from well below ground. They can also be purchased where you would buy bonsai equipment. Soft slate or sandstone will crumble quickly, so would not be a good choice. A stable, hard rock such as granite, would be fine. Look for one with lots of cracks and fissures, a rough surface and an appearance of age and character. The size of the rock will determine the final appearance of the bonsai. A large plant on a smaller rock will give the impression of closeness and a healthy, large tree. A smaller plant on a larger rock will appear to be farther away - a struggling tree dwarfed by the massive rocks. Leaf size should also be taken into consideration. The proportion of plant size, leaf size, rock size and pot size combine to give different messages.

Press a mixture of soft, moist clay and fine peat into the cracks of the rock to give the plant's roots a medium to grow in. The soil is gently removed from the root ball of the plant, to expose the roots, and it is placed on one side of the rock, in an indentation. Try to visualize the plant as it will be after it is pruned and shaped, in relation to the shape of the rock. It could take several tries to find the best position. The roots are tucked into the cracks, and flat polyethylene ribbon or narrow strips of nylon stocking are tied around the rock to hold them in place. Plastic wrap can also be wrapped around the top portion of the rock to hold the roots snugly and maintain humidity around the exposed roots. Small anchorage wire loops can be fastened to the rock with epoxy cement, to hold a root in a specific spot. It is important to keep the roots moist during this time, by misting regularly.

The container we choose could be a deep, inexpensive, thin plastic pot, or a similarly-shaped plastic bag with some drainage holes added at the bottom. The rock and plant are placed in the container and porous soil is added to almost reach the top. Very gradually, over a period of months, or even years, the top of the bag or pot is rolled down or cut off, a little at a time, to expose the roots. During this time, no vegetative pruning is done, as top growth promotes thickening of the trunk and root development. Care is the same as for any other bonsai, except that a fertilizer a little higher in phosphorous (the middle number) is used to promote root growth.

When sufficient roots have been exposed, the rock may be placed into an attractive pot, but this pot should be deeper than a typical bonsai pot, and the rock buried enough so that the roots still have soil around them at the bottom. Once there are enough roots at the bottom of the rock to reach out into the soil and sustain the plant, it is planted into a shallow bonsai pot appropriate for that plant. Now it is time to begin pruning and shaping the plant, to exhibit the characteristics you have been visualizing all along! It may be shaped to appear to be clinging to the rock for protection from the elements and its very survival. Or it may be one of those trees you occasionally see in the mountains, defying all odds, gracefully reaching upwards and outwards to the sun, entirely oblivious to the fact that 'it can't do that!'. By this time, you will have spent many hours on its care, so it is quite appropriate to spend many more gradually shaping it to echo a picture in your mind.