This is what I could find on the subject.
One of the most persistent myths in marijuana lore concerns grafting Cannabis to its closest relative. Humulus, the hops plant of beer-making fame. The myth is that a hops scion (shoot or top portion of the stem) grafted to a marijuana stock (lower stem and root) will contain the active ingredients of marijuana. The beauty of such a graft is that it would be difficult to identify as marijuana and, possible, the plant would not be covered under marijuana statutes. Unfortunately, the myth is false. It is possible to successfully graft Cannabis with Humulus, but the hops portion will not contain any cannabinoids.
In 1975, the research team of Crombie and Crombie grafted hops scions on Cannabis stocks from both hemp and marijuana (Thailand) plants 205. Cannabis scions were also grafted to hops stocks. In both cases, the Cannabis portion of the graft continued to produce its characteristic amounts of cannabinoids when compared to ungrafted controls, but the hops portions of the grafts contained no cannabinoids. This experiment was well-designed and carried out. Sophisticated methods were used for detecting THC, THCV, CBD, CBC, CBN, and CBG. Yet none of these were detected in the hops portions.
The grafting myth grew out of work by H.E. Warmke, which was carried out for the government during the early 1940's in an attempt to develop hemp strains that would not contain the "undesirable" drug 58. The testing procedure for the active ingredients was crude. Small animals, such as the water flea Daphnia, were immersed in water with various concentration of acetone extracts from hemp. The strength of the drug was estimated by the number of animals killed in a given period of time. As stated by Warmke, "The Daphnia assay is not specific for the marijuana drug ... once measures any and all toxic substances in hemp (or hop) leaves that are extracted with acetone, whether or not these have specific marijuana activity." Clearly it was other compounds, not cannabinoids, that were detected in these grafting experiments.
Unfortunately, this myth has caused some growers to waste a lot of time and effort in raising a worthless stash of hops leaves. It has also leg growers to some false conclusions about the plant. For instance, if the hops scion contains cannabinoids, the reasonable assumption is that the cannabinoids are being produced in the Cannabis part and translocated to the hops scion, or that the Cannabis root or stem is responsible for producing the cannabinoids precursors.
From this assumption, growers also get the idea that the resin is flowing in the plant. The myth has bolstered the ideas that cutting, splitting, or bending the stem will send the resin up the plant or prevent the resin from going down the plant. As explained in our discussion of resin glands in section 2, these ideas are erroneous. Only a small percentage of the cannabinoids are present in the internal tissues (laticiferous cells) of the plant. Almost all the cannabinoids are contained and manufactured in the resin glands, which cover the outer surfaces of the above-ground plant parts. Cannabinoids remain in the resin glands and are not translocated to other plant parts.
We have heard several claims that leaves from hops grafted on marijuana were psychoactive. Only one such case claimed to be first hand, and we never did see or smoke the material. We doubt these claims. Hops plants do have resin glands similar to those on marijuana, and many of the substances that make up the resin are common to both plants. But of several species and many varieties of hops tested with modern techniques for detecting cannabinoids, no cannabinoids have ever been detected 212.
The commercially valuable component of hops is lupulin, a mildly psychoactive substance used to make beer. To our knowledge, no other known psychoactive substances has been isolated from hops. But since these grafting claims persist, perhaps pot-heads should take a closer look at the hops plant.
Most growers who have tried grafting Cannabis and Humulus are unsuccessful. Compared to many plants, Cannabis does not take grafts easily. Most of the standard grafting techniques you've probably seen for grafting Cannabis simply don't work. For example, at the University of Mississippi, researchers failed to get one successful graft from the sixty that were attempted between Cannabis and Humulus. A method that works about 40 percent of the time is as follows. (Adapted from 205)
Start the hops plants one to two weeks before the marijuana plants. Plant the seeds within six inches of each other or start them in separate six-inch pots. The plants are ready to graft when the seedling are strong (about five and four weeks respectively) but their stem has not lost their soft texture. Make a diagonal incision about halfway through each stem at approximate the same levels (hops is a vine). Insert the cut portions into each other. Seal the graft with cellulose tape, wound string, or other standard grafting materials. In about two weeks, the graft will have taken. Then cut away the unwanted Cannabis top and the hops bottom to complete the graft. Good luck, but don't expect to get high from the hops leaves. {Smoking any plant's leaves will give a short, slight buzz.}
