A variety of plants and vegetables have been grown commercially in greenhouses for decades. Follow that model when scaling up a greenhouse for the purpose of growing cannabis.
By Shane Hutto
As the cannabis market sees a huge influx of cash, with investors all wanting a piece of the pie, many new grow facilities will be looking at the greenhouse option. I can argue until I’m blue in the face as to why the greenhouse is the correct option over a warehouse, but realistically people just haven’t seen what’s possible in a greenhouse.
Most of the cannabis greenhouses, and even some of the large warehouses are simply scaling up from using the basement growing model, with hand-watered pots on the floor. This makes absolutely no sense when it comes to a commercial production environment. First, we can all understand why watering should be fully automated. Next, we need to look at utilizing every bit of available growing space and getting the very most out of that footprint we can.
When you’re setting up a high-tech facility, should you try and reinvent the wheel or look at what has already been done? The easy answer is use the existing model that has already been optimized and perfected. So let’s talk tomatoes!
Tomatoes have been grown using hydroponic methods in greenhouses for decades. Now, with technology advances, crops are producing higher yields than ever. Cannabis is no different. We can use the same modeling, equipment and technology to give a greenhouse the highest possible output.
Using the tomato model is not easy, but it is the right way to go. You may pay more for a consultant and the equipment up front, but your lowered labor costs and higher yields will drastically increase your profits.
When specifically using the tomato model, there are two primary options for substrate. First and foremost is stone wool, this product is specially designed to give the grower ultimate control over the root zone. Your other substrate option is coco. When I talk coco, I don’t mean the bricks or loose fill bags you buy in your hydro store, I am talking the professional grower’s coco, slabs and blocks. Many of our cannabis growers don’t even know these exist, let alone where to get them. I’ll get into that in a minute.
Next, look at what your slabs are sitting on. The pros don’t use tables or sit their plants on the floor. This is just unsanitary and tables are a pain in the butt, plus once the crop is flowering, it shouldn’t be mobile. The crop should stay in place once flowering is initiated and preparations should be made for stabilizing the top heavy branches.
Whatever method of stabilization you choose, whether it is a trellis or hooks and twine, it should spread the canopy to get maximum light penetration as well as cover the entire footprint allotted for each plant. For those of you wondering about the hooks and twine, it is essentially a yo-yo that attaches the string to the plant and can wind around the yo-yo like a hook as the plant grows taller. This is an excellent method for low-stress training, particularly in a greenhouse. This method is used widely in the commercial vegetable model.
Once you’ve got plants in media, you’ve got to feed them. Professional greenhouses don’t feed by hand whatsoever, so why on earth would cannabis be any different? It’s not. It’s a matter of knowing what automated technology is available, and not only how to use it, but how to get it and how to install it. Also, sometimes your structure may have to be adapted so the technology conforms to building/fire code. There are tons of automated irrigation systems, and any commercial cannabis grower should have a custom irrigation plan to meet the designs of their facility. The key is having the right consultant to help you plan a retrofit or do a new overall design. The consultant should have access to all the suppliers already for any products he recommends to you and should be able to use those contacts to get you the best deal.
So now you’ve got the plants taken care of, but what about lighting? If you’re using a greenhouse, you are obviously going to use as much natural sunlight as possible. However a major misconception is that a professional greenhouse doesn’t need lights. This is wrong. A commercial cannabis greenhouse will have lights throughout, simply for photoperiod control; they will also be utilized during low-light days as an additive source of energy to maintain plant growth rates. Automated blackout cloths will likely need to be used because the hours of sunlight per day are often too many for flowering cannabis. These cloths can even black out individual zones at different times. The real key is knowing how to manage the photoperiod, temperature and humidity using these technologies in conjunction with each other.
If you decide to go the greenhouse route, you’ll want to hire a greenhouse contractor. There are a number of them now that are very willing to sell to cannabis growers. Be careful though because you will get what you pay for. The cheapest greenhouse manufacturers are famous for building your structure and walking away without installing all the ancillary equipment. These cheapies are also not really designed in conjunction with the high-tech systems that are available. One major requirement is wall height. The higher the ceilings are, the more suitable the structure — not because we are growing particularly tall plants, but because the high ceilings allow us easier control over the temperature and humidity, especially in time of extreme temperature. For example one of the biggest issue growers run into is during the winter. Greenhouses can get too hot from the heaters running in the morning and then the sun continuing to increase the temps. Then they need to vent to decrease temperature, but because it’s cold outside and warm in the greenhouse the vents won’t work properly in all cases. Often the greenhouse will fill with fog or condensate and completely screw your humidity balance. We all know this is a major problem for cannabis during flowering so the tall peak heights can curb the effects of this issue to some extent.
The things I have mentioned here are truly only the tip of the iceberg and the technology being employed in the commercial market is far better than what most cannabis growers are doing. I hope that this read has given you a wider eye to not just follow convention of cannabis, but follow convention of agriculture; after all, we are just growing flowers!
Shane Hutto is the owner of Horticultural Solutions, a consulting firm based in Colorado. He specializes in high-tech greenhouses and large-scale warehouses, as well as other aspects of the cannabis industry.