Soil: First and foremost, invest in top-quality soil as this will impact the entire growing process. Pick a nutrient-packed soil that contains organic substances like compost and worm castings. Pay attention to the pH levels of the soil as well — aim for a range of 5.8 to 6.3. Other qualities to look for in soil include good drainage ability, high oxygen levels, and effective water retention. You could also make your own super soil.
Climate: In addition to protection from rain and wind, marijuana greenhouses can contain climate control equipment like dehumidifiers, exhaust fans, and heating and cooling systems. With the help of these tools, greenhouses can extend the growing season and allow for year-round cultivation.
Think about the storage space you’ll need for your greenhouse setup, including supplemental lighting and nutritional blends. You’ll also need an easily accessible place to store water and soil, so that the greenhouse is a one-stop location for all your cannabis cultivation items.
The key word when it comes to cannabis growing in a greenhouse is control. Photo by: Damien Robertson/Weedmaps
When planning to build your own marijuana greenhouse, consider which material will create the ideal environment for happy plants. While glass is the traditional material, you can also use fiberglass or plastic. The latter two will be equally effective but not as fragile or expensive. Whichever material you choose, make sure you install proper ventilation to release trapped heat and let your plants breathe.
Polytunnel: These elongated, dome-topped greenhouses have an aluminum frame and a covering of polythene. They are usually big enough to walk into but not as sturdy as actual greenhouses. Accordingly, polytunnels are on the lower end of the price range, starting at around $160. These can be durable but do need some maintenance, especially replacement of the cover every three to five years.
The key word when it comes to growing cannabis in a greenhouse is control. Greenhouse cultivation provides the natural sunlight, fresh air, and other benefits of growing outdoors while eliminating the unpredictability of Mother Nature. Periods of rain and wind can wreak havoc on your weed garden, but a greenhouse protects plants from the elements. Likewise, pests, bacteria, and diseases are less likely to invade your plants in the shelter of a greenhouse.
Once you have the best greenhouse for you, it’s time to put your cannabis cultivation skills to the test. Here are the most important aspects of growing top-quality weed in a greenhouse.
Whether it’s a simple walk-in greenhouse or something more elaborate, check local laws to see if building permits or other formalities need attention before you start building.
When growing with good cannabis 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 ample root space. Remember too that a few seeds could provide a years worth of medication or recreational weed, so regard the cannabis seed as an investment and get a good variety. Cannabis seeds are one area of your life where you really don’t need to compromise. Look at the Dutch Passion website for some cannabis cup winning options. Proven varieties for greenhouse growing, especially at northern latitudes, includes Shaman, Durban Poison, Passion #1, Frisian Dew and Frisian Duck. These varieties have been used by numerous repeat growers over many years. They have passed stringent standards for potency, quality, pest/mold resistance and vigour. Growing these feminized seeds in a greenhouse will deliver excellent results.
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.
Many greenhouse growers also arrange a hosepipe/water connection near their greenhouse. This simplifies the process of getting water to your plants. The last thing you need on a hot day is numerous long walks from your house to the greenhouse with a watering can.
Early flowering using a ‘darkening system or extending your growing season
Plants that are rooted directly in the ground obviously can’t be moved, but will survive well even when you are away for a week or two. There is less need to worry about daily watering. If your greenhouse contains good quality moist soil then your cannabis plants will establish an extensive root network which will support a large plant with heavy yield potential. However, if the ground under the greenhouse contains poor quality soil then remove it and replace with good quality soil before growing plants in it. Serious greenhouse growers will dig in plenty of manure and compost at the end of each growing season to ensure optimized soil quality for the following years crop. One advantage of rooting your plant directly into the ground is that you can grow very large plants with unrestricted root space. It’s one way to get XXL harvests. Some greenhouse growers, when using the best cannabis seeds, find that a single plant can occupy the entire greenhouse and occasionally even run out of space. If this happens you can try low stress training to tie down the taller branches. In extreme situations, some growers have even had to remove some roof panels from their greenhouse if the plant grows uncontrollably. Plants which are rooted directly into the ground can be grown using automated feeding systems such as dripper systems etc.
Many greenhouse growers enjoy large harvests of over 100g (dried buds) from each autoflower plant. The protective environment of a greenhouse protects the autoflower plants from the worst of the weather and the extreme low temperatures which can occur especially in early spring and autumn.
Greenhouses also have the benefit of allowing the grower to extend the end of the 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.
Greenhouse grown cannabis versus outdoor cannabis
The experienced grower can use the benefits of a greenhouse to grow larger plants, with improved quality and a longer life cycle. Plants can be started earlier and harvested later thanks to the extra protection offered by the greenhouse. During the cultivation process the conditions inside a greenhouse are better than those outside, promoting improved plant health, superior yields and better potency. Outdoor grown plants, without these benefits, usually offer lower yields and quality.
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 more frequent watering and occasional feeds. A large cannabis plant in a 10 litre container will need watering daily during very hot weather. That could be a problem if you are away and unable to visit your plants.