Field Notes
On October 5, 2000, members and guests of the Philadelphia Society for Promoting Agriculture toured the C.P. Yeatman & Sons, Inc. mushroom production facility located in Kennett Square, Pennsylvania. This farm is one of the older mushroom production operations in this southeastern Pennsylvania area. The Yeatman family has been operating the farm since 1921 and the fourth generation is currently managing operations.

The farm consists of 22 houses containing over 150,000 square feet of bed space. with surrounding acreage used to produce the hay for compost. The houses are air-conditioned and closely monitored. Yields average over seven pounds of mushrooms per square foot per crop and there are 4.7 crops produced per year per house.

The farm is a Pennsylvania State licensed organic farm on which no pesticides or chemical fertilizers are used. For insect control in and around the mushroom houses, suspensions of a parasitic nematode are used for small fly control, and a parasitic wasp is used for control of houseflies.

The compost from which the mushrooms are produced is made from equal portions of straw bedded horse manure and mulched hay which is supplemented with cottonseed hulls, chicken manure and gypsum. The use of manure in compost eliminates a disposal problem that would otherwise be present at the sources. After the compost has been placed in the beds and spawned with the mushroom fungus, it is cased with a thin layer of material made from shredded sphagnum moss, lime and ground limestone.

All wastewater is collected, drained into a central holding tank and recycled for irrigation/fertilization of the hay fields. The spent compost that remains after the mushrooms have been harvested is spread on hay fields as a slow-release organic fertilizer, or it is sold to potting soil distributors.

Mushrooms are vacuum-cooled immediately after picking, sorted, packaged and held at 40° F until and during shipment.

The Yeatmans currently produce the white mushroom, Agaricus bisporus, although they have grown some of the exotic species – oyster, portobello, maitake, crimini – in previous years. A worldwide glut of mushrooms, exacerbated by virtually unrestricted importation from Mexico, Taiwan and other Oriental sources has depressed prices and almost eliminated the premium paid for organically grown mushrooms.