The following requirements specifically apply to scion blocks of containerized plant genera Amelanchier, Chaenomeles, Cydonia, Crataegus, Malus, Prunus, Pyrus, and Sorbus species:

1. (1) The roots of trees being containerized must be free of soil prior to planting in the containers;
2. (2) The growing medium must consist of nonsoil material including, but not limited to, expanded or baked clay pellets, ground coconut husks, coffee hulls, cocoa pods or rice husks, peat, perlite, sawdust, sphagnum, volcanic ash, cinder, or vermiculite. The components of the growing medium must not have been previously used for growing plants or other agricultural purposes. The components of the growing medium must be mixed and maintained under conditions which preclude soil contamination or contamination by water run-off. Samples of the growing medium may be taken to verify the absence of soil.
3. (3) The containers must be set on a barrier that prevents the roots of the plants from permeating the soil or prevents direct contact with the soil, such as plastic, hard-packed clay, pavement, or a minimum of two inches of coarse gravel. The site must be located so as to preclude soil contamination, either directly or through water run-off from drainage, flooding, irrigation, or other means.
4. (4) All other requirements for growing scion blocks must be met (see WAC 16-350-025).

[Statutory Authority: RCW 15.14.015. WSR 26-10-008, s 16-350-033, filed 4/27/26, effective 5/28/26.]