Rice hulls are a great, sustainably sourced material for drainage/aeration. Unlike coco chips, rice hulls are very fine in texture, which makes them great for plants with fibrous roots like begonias. The concave shape of the hulls allows the soil to maintain aeration due to small air bubbles trapped in the hull.
Please note: these hulls are not boiled and contain occasional grains of rice which may sprout. We don't use boiled hulls because they break down too quickly in soils.