Growing Cannabis in a Greenhouse

The recent explosion in ‘growing your own’ cannabis includes the rapidly growing army of greenhouse growers. Growing cannabis in a greenhouse removes the complexity of designing an artificial indoor grow room. For many it is safer, more predictable and easier than growing outdoors. Greenhouses offer protection from the elements and provide a longer growing season, allowing growers in northern European regions the ability to grow crops either with traditional or autofem seeds.

Greenhouses can be heated if needed and with a little bit of thought and planning growing cannabis in a greenhouse can be a safe, secure and pleasurable way for the home-grower to be self sufficient in recreational or medical ganja. Greenhouse-grown cannabis is incredibly potent when grown from good seed stock and more people than ever are growing in greenhouses and enjoying the benefits.

Greenhouse growers are split into two main groups; those that grow their cannabis plants in plant pots and those that grow them directly in the ground. Plant pots can be easily moved if they need to be, for example if visitors, extreme weather or other problems are present. But plant pots will need watering and occasional feeds. Plants that are rooted directly in the ground obviously can’t be moved, but may survive well even when you are away for a week. If the ground under the greenhouse contains poor quality soil then remove it and replace with good quality soil before growing plants in it. Some greenhouse growers even run hydroponic systems very effectively in their greenhouses.

Sophisticated greenhouse growers have watering systems in place to simplify and even automate water delivery. If the greenhouse is not in an entirely private location then it might benefit from a coat of white shading paint. This is sold in garden centres and used to protect greenhouses from overheating on the hottest summer days. For the cannabis grower this shading paint also stops people seeing what is inside your greenhouse, but green plastic plant mesh and tomato plants have also provided excellent cover for many generations of greenhouse growers that hide the occasional cannabis plant in a secluded corner of the greenhouse.

Anyone that has been in a greenhouse on an early spring day will note how quickly they warm up in sunshine. This allows growers to get their preferred marijuana varieties started earlier than they could outdoors. So the growing season starts early which allows the greenhouse grower to benefit from larger plants and subsequently superior harvests. Cold nights can be mitigated with the use of greenhouse heaters that are available to purchase at any garden centre.

Just as with outdoor grown cannabis, the shift towards shorter days during the summer is a signal to the cannabis plant to start flowering and produce the desired female buds.

If the greenhouse grower can get good soil for his plants and (most importantly of all) start with good seed genetics then the plants can grow into true monsters by the end of the grow season. The greenhouse grower can see cannabis plants reach sizes rarely seen indoors. Many greenhouse growers have grown single plants that have filled small greenhouses and produced several hundred grams of top quality weed per plant. Some greenhouses have windows that will open and let the plants grow out, but a safer option is to use cord to try to ‘tie down’ the plants if they do start growing massively. The photo below shows what can happen when a prolific strain starts to turn into a large bush that wants to grow as high as a small tree. The plant simply becomes too tall for the greenhouse.The soil conditions, temperatures and good care resulted in a plant that was thriving as if in the jungle rather than a garden in northern Europe. Of course this type of success rarely occurs when cheap seed is grown in poor quality, poorly prepared soil. The grower here had properly dug, conditioned and prepared the soil at the start of the season and in our opinion reaped the reward at the end of the growing season. He was growing the Dutch Passion Shaman variety that was bred for specifically for outdoor/greenhouse conditions. The Shaman variety combines some incredibly potent skunk/purple skunk parents. In the photo the plant eventually grew into a bush 3 metres tall and two meters wide. A real beauty that won one of our photo contest awards in 2006. In this case the grower was forced to remove a pane of glass from the greenhouse as his resin soaked Shaman outgrew the tall greenhouse. The plant was too strong to be tied down, and security was not a problem on this particular grow so the grower went on to harvest an abundance of excellent stash despite the obvious size problems of the Shaman.

When growing with good seeds in a greenhouse remember that some plants will grow as wide as they are tall especially if they have plenty of sun, good soil and plenty of root space. Remember too that a few seeds could provide a years worth of medication or recreational weed, so regard the seed as an investment and get a good strain. This is one area of your life where you really don’t need to compromise. Look at the Dutch Passion website for some ideas, there are some proven strains that have passed stringent standards for potency, quality and vigour.

Some growers equip their greenhouses with a ‘darkening’ system. Essentially this involves using dark blinds/curtains to create blackout conditions inside even when it is sunny outside. This can be used to simulate short summer days and ‘force’ the plants to start flowering and producing buds much sooner than normal. Although this involves extra expense it is one way of accelerating greenhouse weed production. The grower simply uses the blinds to reduce daily light exposure to 12 hours (or less) and the plants in the greenhouse respond by flowering.

Greenhouses also have the benefit of allowing the grower to extend the end of his growing season. Cold sunny autumn days on the outside become warm and comfortable in a greenhouse and allow plants to ripen properly. Pests are normally easy to control in a greenhouse, and so long as the greenhouse is secure it is a great and simple way of growing.

Many also grow weed in polytunnels these days, the benefits of the poly tunnels being much the same as greenhouses. Polytunnels protect against the worst of the elements, keeping the plants safe and giving a long growing season. Polytunnels come in a wide range of sizes and they also offer privacy to the grower.

The growth in cannabis use, both medical and recreational, has been extraordinary over the last few decades. That growth continues today where cannabis is increasingly seen as a less damaging recreational drug than alcohol and a non-addictive one in contrast to tobacco. Unlike either alcohol or tobacco, cannabis is also being rediscovered as an increasingly important medicine after a century of prohibition. Up until the prohibition of cannabis that began in the 1930’s it is estimated that every US citizen in the preceding 100 years would have used some form of cannabis medicine either as dried bud, tablet, liquid extract or impregnated sticking plasters.

What is also interesting, taking Europe as an example, is that cannabis imports from Asia, Africa and South America have more or less completely collapsed in recent years. Instead Europe is now growing the vast bulk of its own cannabis from seed. Much of this is coming from greenhouses and many of these belong to private individuals becoming self sufficient. You might expect that the misguided government policies that made cannabis illegal would have handed control of the cannabis industry over to organised criminal gangs just as American prohibition of alcohol handed control of alcohol (and revenues) to the mafia. Yet cannabis seems to have escaped from the grip of the criminal world that runs the hard drug business. Instead cannabis has found its ways into private greenhouses, indoor growrooms and countryside fields and here it will surely stay.

Rather than harass those who grow the seeds, governments and police should be grateful that cannabis is no longer generating such huge profits for the criminals who used to run its import and supply. The man who grows and consumes his own weed is neither a social threat nor criminal menace. Cannabis consumption in many countries remains a curiously unique ‘crime’ in that there is no victim. Fortunately attitudes are changing, and in any event recreational and medical cannabis are here to stay.

Growing cannabis in a greenhouse is a simple and effective way towards self sufficiency. Judging by the increasing number of internet forums, greenhouse growing also seems to be a rapidly expanding pastime amongst growers of all backgrounds in a wide range of countries.

The more professional greenhouse grower will take care to introduce new, good quality soil each year and keep the greenhouse clean and tidy to minimise potential for pests and disease. Some greenhouse growers use strategically placed fencing and shrubs to make the greenhouse inaccessible to unwanted visitors and invisible to prying eyes. Greenhouses are cheap to buy, they are available everywhere and come in any shape/size required. Some of the modern polycarbonate greenhouses are also opaque giving instant privacy and have lockable doors. What more could you need in your back garden? Just remember that poor seeds always give poor weed, invest in the best you can get.