Colorado Lava Rock Granules Bonsai Tree Soil Additive - 2 lbs. (1 Qt.)
Lava Rock is a naturally occurring volcanic cinder that has a porous structure which makes the material lightweight and highly moisture retentive. Incorporate into your bonsai soil mix to increase drainage (aeration). It will absorb up to 40% of its weight in water. Small lava rock (1/4 inch) is the best "sand" component around because it is "sharp" and has very irregular surfaces.