How to Grow a Bonsai Around a Rock

by Jonathan Brandt

Question: I love the look of bonsai roots growing around a rock. Can you tell me how to achieve that?

Ficus Bonsai Tree - Root Over Rock - (ficus natalensis)

Answer: If you have mastered the basics of growing bonsai, you may now be ready to learn how to grow a bonsai around a rock.

Root over rock is one of the most dramatic and interesting bonsai forms, and although it is not necessarily difficult, it does require extreme care and patience. This style is designed to depict a tree in nature that has grown in a rugged or mountainous area and has had to stretch its roots over rock or rough terrain in order to find sufficient nutrients.

The goal of the root over rock form is to make sure that the roots grip the rock securely as the stone will be your tree's only source of stability. Since very little soil is used, one of the most difficult challenges of this style is ensuring that your plant receives adequate support, making both your choice of rock and use of proper technique vitally important.

Supplies Needed

Before you begin your project, it is important that you have the necessary supplies to create bonsai around a rock. You will need:
  • A rock: You can find a suitable rock on local terrain or you can purchase one at a nursery or quarry. Make sure that it is an appropriate size for your finished product and has plenty of natural hallows and crevices. You can use a chisel to make extra depressions if necessary. Unlike a bonsai pot, the rock will become a permanent features, so it is important that you choose well.

  • A plant or tree: It is best to choose a plant that can be easily grown in this style and will suit both your choice of rock and artistic vision. Your tree must have a long, extensive root system that can be easily draped and wrapped around the rock. If the tree does not have long enough roots, you can plant it in a tall, thin container that will encourage the roots to grow downward rather than spreading out. Leave it for about a year, or until the roots have reach a suitable length, about one and a half times the height of the rock you will be using.

  • Securing material such as grafting tape, plumbing thread tape, raffia, or copper wire.

  • Scissors and/or pruning shears

  • Concave branch cutter (depending on size of tree and pruning necessary)

  • Root hook/fork

  • Bonsai soil

  • Chopsticks

Professional Bonsai Tool Set - 6 Piece Plus Hemp Brush

How to Grow Bonsai Around a Rock

    1. Clean your chosen rock so it is free of dirt and debris.

    2. Carefully remove the tree from its pot. Gently brush away as much soil as possible from the root system by hand and then wash the roots with a hose. The closer to the rock that the roots can be attached, the better. This is a very delicate procedure, so take care not to cause any damage or injury.

    3. Using a root hook, carefully untangle the roots and inspect the root system.

    4. Using sharp pruning shears, cut away any dead, dying, thin, or rotting roots as well as those that cross over each other.

    5. Place your plant over the rock and carefully experiment with various positions until you find the one you like the best. Remember to place roots in hallows, crevices and cracks as they would appear in nature, and keep in mind that they should also follow the natural water path. Try not to place all the roots in one place because you will want your bonsai to be viewed from all directions.

    6. Attach the roots to the rock. Some people prefer to tie the roots down with raffia or copper wire before covering with grafting tape. You may also find it helpful to have someone hold the roots in place while you secure them to the rock surface. Wrap grafting tape gently around the rock, making sure to cover the roots entirely except for the bottom where they will grow into the soil. Inspect to make sure that there are no gaps where the roots can escape or get through the tape.

    7. Repot the bonsai in an container large enough for your chosen rock. Fill all holes and cracks with bonsai soil and make sure to cover all the roots completely to encourage quicker growth. No parts of the rock or root system should be exposed.

    8. Trim your tree immediately to balance any root pruning you may have done and remove any unhealthy or vigorously growing branches and stems. Cutting back your plant's foliage will also lessen the demand on its root system, giving the tree time to recover.

    9. Water the tree well and leave it in its training pot for at least one year. If you have a very fast growing plant, the roots may attach quite nicely in a year's time; however, some trees will need longer.

    10. Gently remove the bonsai from its container and brush the soil away from the roots, being careful not cause any damage. Use a sharp pair of scissors to cut away the grafting tape, making sure not to cut through any roots. Use a chopstick to removing any remaining soil then wash the rock and root ball, and inspect to make sure the roots have bonded well to the rock.

    11. Repot your root over rock bonsai in a suitable container and fill with new potting soil.

Growing bonsai around a rock is a very delicate process that requires extra care and patience. But, the finished product will be a unique work of art that will make all the time and effort worth the investment.

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