Temperature at time of collection has no effect on eventual grafting success. However, grafting wood should not be collected when wet unless the surface is allowed to dry thoroughly before storage. Scionwood may be stored dry in ventilated plastic bags in a cooler or refrigerator at or just above freezing. Care must be taken so that condensation does not form on the scion inside of the bags. If it does, remove the scion, and allow the surface to dry.
Excessive moisture encourages mold and fungus growth which damages the buds.
In fact, scionwood can be stored for up to three months on the cooler shelves without plastic bags. Below freezing temperatures from 20 F to 32 F may provide up to six months storage, but scionwood must be placed in nonvented, sealed plastic bags. Grafting An extremely sharp grafting knife is a must. Walnut wood is very hard compared to other commonly grafted woody plants and requires a great deal of control, strength, and practice for the proper cuts. The rootstock should be cut first.