Intergeneric grafts between Cannabis and Humulus (hops) have fascinated researchers and cultivators for decades. Warmke and Davidson (1943) claimed that Humbles tops grafted upon Cannabis roots produced ". . . as much drug as leaves from intact hemp plants, even though leaves from intact hop plants are completely nontoxic." According to this research, the active ingredient of Cannabis was being produced in the roots and transported across the graft to the Humulus tops. Later research by Crombie and Crombie (1975) entirely disproves this theory. Grafts were made between high and low THC strains of Cannabis as well as intergeneric grafts between Cannabis and Humulus, Detailed chromatographic analysis was performed on both donors for each graft and their control populations. The results showed ". . . no evidence of transport of inter mediates or factors critical to cannabinoid formation across the grafts."
Grafting of Cannabis is very simple. Several seedlings can be grafted together into one to produce very interesting specimen plants. One procedure starts by planting one seed ling each of several separate strains close together in the same container, placing the stock (root plant) for the cross in the center of the rest. When the seedlings are four weeks old they are ready to be grafted. A diagonal cut is made approximately half-way through the stock stem and one of the scion (shoot) seedlings at the same level. The cut portions are slipped together such that the inner cut surfaces are touching. The joints are held with a fold of cellophane tape. A second scion from an adjacent seedling may be grafted to the stock higher up the stem. After two weeks, the unwanted portions of the grafts are cut away. Eight to twelve weeks are needed to complete the graft, and the plants are maintained in a mild environment at all times. As the graft takes, and the plant begins to grow, the tape falls off.
