By Sally Brown, University of Washington

We finally took the plunge.  While buying cannabis is legal in most of the Northwest, growing it in a University is not.  Universities receive funds from federal agencies and the feds frown on legal cannabis.  That has essentially stopped any research on cannabis on campus.  In order to grow legally, you have to apply for a permit and then wait on a long list until one day you are allowed to grow a strain that is produced in a federal facility in Alabama (maybe Mississippi).  That strain is as old and outdated as the ‘loco’ weed some of us knew back in high school.  

Instead of applying for a permit, we made the switch from cherry tomatoes to hemp.  Our first attempt to buy hemp seed on line got us some type of legume.  With the second try we were able to purchase hemp seed out of California that looked and smelled like the real deal.  The seeds were planted in Tagro, Tagro + biochar, and Happy Frog (shown below from left to right).  Happy Frog is a commercial soil blend that is used by container cannabis growers.

greenhouse trials

The pots were set up in the greenhouse in a randomized complete block design with 4 replicates.  While hemp is different from cannabis to the untrained eye, the two plants are very similar.  As our trail began to take root, the aroma in the middle chamber of the greenhouse at UW was strikingly similar to what you would expect at a cannabis growing operation.  There were no signs of pilfering and I only got one email from another faculty asking what exactly we were growing.  The plants flowered, had plenty of pollen and we decided it was time to harvest.

hemp resuults

As with the prior studies using cherry tomatoes as a surrogate, both Tagro based mixes far outperformed Happy Frog.  Biomass and number of buds for both Tagro products were much higher than in the commercial growing media.  In fact seedlings in two of the four Happy Frog pots barely germinated and were only a few inches high at the time of harvest.  There was no statistical difference between the regular Tagro and the Tagro + char.  With that said, adding the char may have added a minimal benefit- certainly enough to create a designer ‘growers blend’ if one so desired.  After many tries with tomatoes, we can now say that the results we saw with tomatoes can be applied directly to hemp. Biosolids based soils appear to be an excellent choice for cultivating cannabis.  Let the new market take hold!