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Tip of the Week  #14

"Root Over Rock" Planting

Welcome to our next installment of  "Tips Of The Week".

This feature is for the benefit of visitors to this site, I would be happy to hear from you if there is something you would like to see covered here in future weeks. Please direct your E-mail to let me know if I should include your first name, last name, city, E-mail address or no acknowledgement.

Interested in past articles? There's a list at the bottom of the page.

If you've had the good fortune to see a full sized tree with it's roots growing over a boulder, you understand why the "Root Over Rock" or "Rock Clasping" style is so prized by bonsai people. As with all good bonsai styles, it copies things that happen in nature. When a seed sprouts from the ground, thick "anchoring roots" form, and grow down and slightly outward from the trunk. If a root meets a rock, it grows along the rock to the edge, then continues its downward journey. If there is a boulder a few feet beneath the surface, all the "anchoring roots" grow along the rock in an outward pattern away from the trunk. If the weather conditions and/or terrain cause soil erosion, you have a candidate for a natural "root over rock" tree. It can take decades, or even centuries for the eroding soil to expose the boulder being grasped by the thick, gnarled roots, but when it happens, it's a sight to behold.

To copy this style, you'll need a tree that develops thick roots and can be bare-rooted, a deep bonsai pot, some live moss, and some fast draining bonsai soil. Maples are good temperate-climate candidates, and Serissas are good sub-tropical candidates. You'll also need a good rock. Try to find one that's egg shaped, and between 5 and 12 inches from top to bottom.  If it has grooves & crevices running from top to bottom, that's a plus, but a smooth one will do just fine.   If you need to "anchor" the roots to the rock, but don't want to damage the rock, try this. Cut a 2 inch piece of wire and place one end in the crevice where the root to be anchored will go. Put a few drops of silicone or epoxy over the wire to secure it in place, and allow it to dry for 24 hours. Put the root in the crevice, bend the wire over the root, and it will stay put. When that portion of the rock is exposed, unbend the wire. If the root stays in place, remove the wire, chip or scrape away the silicone or epoxy, and your rock is as good as new.

You'll also need some "peat muck". To make "peat muck", you put some peat moss in a medium grade (larger than window screen) sieve and shake it. Gather what comes through the sieve, and mix it with water to form a thick paste. Place the rock in the middle of a bonsai pot that's two inches or more deep. Put an inch or so of the fast draining bonsai soil mix in the bonsai pot. Spread the paste in the grooves of the rock, or if it's a smooth rock, cover it completely. Place your bare-rooted tree so that the top of the rock is touching the underside of the trunk, and drape the roots over the rock and down the sides. If the roots are long enough, arrange then in the soil at the bottom, then add soil to fill the pot. Next, cover the entire rock with moss that has been soaked and flattened. (For information on working with live moss, see "Tip Of The Week #12). To water, use a misting bottle. It is important that you soak the moss covered rock. If the moss dries, the roots will die. Spray heavily & often. Water the soil portion the way you water your other bonsai.

A few months after the bonsai begins to grow, peel away an inch or two of moss from the top of the rock. Choose the 4 to 6 roots that will clasp the rock, Cut & remove one or two of the thinnest remaining roots. Every few months remove another inch of moss and another thin root. If in the process of doing this you reach the end of a root that you want to grow into the pot, cover it immediately with moss, and give it a few more months to grow before checking it again. Continue this process until the rock is bare, and all the selected "clasping" roots have grown into the soil at the bottom of the pot. You now have a Rock Clasping bonsai. The roots will seem too thin at first, but with time and good fertilization they'll steadily thicken. Adding a drop or two of Super Thrive in all water will thicken them even faster.

To either change the pot or root prune this bonsai, it is important to think of the rock as part of the tree. It will be decades before the roots are thick enough to completely hold the rock in place. When handling it, hold it by the rock, not by the trunk of the tree.

If there are any parts of this article that are not clear, or if there is something you don't understand, E-mail me at  I'll answer your inquiry, and if necessary, update this article.    The idea for this article came from a reader.    Got a question?    Send it in.

Interested in past articles? Click for your choice below.

#1-Things to do in the spring

#2-Forest Plantings

#3-Planning a trimming schedule

#4-Trimming Japanese Maples (And other trees with opposing Buds)

#5-Trimming Chinese Elms (And other trees with alternating Buds)

#6-Trimming Conifers (Such as Pine, Juniper and Cypress)

#7-Improving Your Bonsai Skills

#8-Things to Remember During the Winter Months

#9-Some Thoughts About Tree Roots. Their Strengths & Weaknesses

#10-Potting Medium: The Foundation of a Bonsai

#11-Growing Bonsai Under Artificial Light.

#12-The Importance of Moss, How To Get It & Put It On a Bonsai.

#13-The Right Tool For The Job

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