Orchid Supply Store uses Black Gold Organic Mushroom Compost. It is an organic and all-natural way to improve your soil. It is a slow release fertilizer, analysis 0.5-0.5-0.5,that will not burn roots and is great for houseplants. Black Gold provides moisture holding capacity to sandy soils and provides aeration and moisture holding capacity to hard, clay-type soils. It is organic and contains nutrients that are released slowly without burning tender roots.