Lady slipper orchids have great potential as a perennial bedding plant in temperate-zone climates Unfortunately, many gardeners fear these species because of their high cost and perceived difficulties associated with growing plants outdoors. The former factor can be addressed by improving the production of plants at the wholesale level. Growers contest that sphagnum peat and coconut coir are poor organic addenda for these species due to their natural acidity. Anaerobic digestion-derived biosolids (ADB) are not acidic like sphagnum peat or coconut coir, and may be the perfect organic addendum for the culture of ladyslipper orchids. Hence, 3-year-old plants of showy (Cypripedium reginae) and yellow ladyslipper (Cypripedium parviflorum var. pubescens) orchids were grown in soilless potting mixes containing vermiculite and perlite plus various concentrations and combinations of ADB and coconut coir. Plants were grown in the greenhouse at 70 ± 10 °F and received normal light and photoperiod during Summer 2005. Growth, as assessed by the dry weight of dormant stem tissue, of showy ladyslipper potted in media containing ADB was three- to four-times greater than those grown in media containing coconut coir. Growth was similar among yellow ladyslippers grown in media containing ADB or coconut coir due to the fact that these plants had produced all their stem growth for the season before the experiment was initiated. ADB has great potential as an organic addendum to horticultural growing media used for the culture of Cypripedium species. Use of anaerobic digester-derived biosolids in horticultural growing media is a protected intellectual property and available for license through the WiSys Technology Foundation.