Cottonseed Hulls and BonsaiThe original cottonseed hulls article appeared in my Bonsai with Tropicals newsletter Issue 1, 1996. Edited and updated for this site. (Thanks for your help Mike!) I first saw bonsai soil covered with cottonseed hulls while observing a program by Mike Kling. He was creating an extensive mini-landscape (including mountains, valleys, streams, rivers etc.) on a large restaurant carry tray. 
It was quite a unique undertaking. Mike attributed much of his success to using these hulls instead of 'muck'. It kept many of his geographical formations in place, and added texture to the landscape. What are Cottonseed Hulls?Hulls are the covering of the actual cotton seed. When cotton is processed, this is what remains. It is then bagged and sold as roughage for animal feed (cows and pigs). Hulls are not to be confused with cottonseed meal, which is used as fertilizer.What Do Hulls Look Like?
Hulls have a very small amount of leftover cotton mixed in, giving them a “fluffy” look and feel (before they are soaked in water). Once they are wet and in place they become darker and have a neutral ‘earthy’ appearance. Moss and other groundcovers should be planted directly in the soil. In time, they will spread over the hulls. What do They Do?In bonsai circles, these hulls prevent soil erosion in shallow saikei landscapes and root-over-rock plantings. They replace the muck mixture which is often so thick roots can barely penetrate it.Cotton seed hulls are a great alternative to muck and in many cases a preference. Another good purpose is a “natural” ground cover to deter weeds - instead of using chemicals. More good news: they are porous, the water drains right through. They are also very clean to work with. Where Did the Idea Come From?Dr. Leon Snyder first discovered the value of cottonseed hulls in his work with micro-environments. He was a frequent guest at bonsai conventions in the 1970s, where he introduced them to the bonsai world.As Dr. Snyder explained “the cotton fibers stick to the hulls much like Velcro”. Therefore, they stick to themselves when patted together. It seemed to especially enjoy the cold winter of 2010, and stayed dormant until early April. In this photo it is just budding out. The roots are prolific and need to be pruned annually. This year I chose a very shallow Japanese container and used cottonseed hulls to keep the soil from washing away. How Are Cottonseed Hulls Prepared?Start with a small amount of hulls. Allow for expansion, they almost double in volume when saturated.SOAK amount to be used in a container of water for at least an hour, best overnight. Take a handful of hulls without squeezing the excess water out and begin lightly placing a thin layer on top of the bonsai soil/rock or other area as needed and tap it in place. Cover all the soil, tapping it on as you go. Place it especially where you want to avoid erosion. During the first couple of hours after placement, occasionally mist or spray lightly with the hose to help the hulls set. Firmly tap them again. Can I Save the Leftovers?Wet? Absolutely NO! There isn’t much that smells worse than “rotten cotton” and it can (and will) attract rodents. When used as recommended it neither smells nor attracts rodents.Store dry leftovers out of the sun and in a closed, air tight container. If kept dry, they last forever. I still have some from ten years ago. What Happens in Time?After several months (possibly more depending upon your climate), cottonseed hulls on soil begin to break down. As needed, they are easily replaced.Where Can I Find Cottonseed Hulls?Try a local farm supply or feed store (not garden centers). If the feed store doesn’t have them, ask them to place a special order for you. Be sure you ask for HULLS, not just seed, or meal.They are inexpensive; however, they are usually packaged in 50 lb. bales. So, find some bonsai friends who share your enthusiasm for experimenting! Top of Page
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I inherited this imported Trident Maple root-over-rock bonsai, and wasn't sure how well it would do deep into Zone 10. It does just fine! 