Supplemental lighting allows the grower to extend the hours of daylight and to improve the quality of light on overcast days. This will give you more control over the vegetative state of your plants.
This greenhouse effect opens up the door to year-round cultivation, but cannabis still needs light from the sun in addition to the warmth that a greenhouse provides.
On a hot day, you experience the science behind a greenhouse when getting into a parked car that has been left in the sun.
Solar radiation (energy from the sun) passes through the transparent walls of a greenhouse and heats up soil and plants, keeping a greenhouse warm even when the outside air temperature is cold.
Cannabis generally goes in the ground outside between April and July, when the sun is out for most of the day. This keeps plants in the vegetative stage.
Advantages of Growing Greenhouse Cannabis
If you want to continue growing cannabis through the fall and winter, you will have to lean more heavily on supplemental lighting and heaters.
Advanced greenhouses can allow you to grow year-round by controlling light. They can provide supplemental lighting when it’s too dark outside and they can block out all incoming light if it’s too light outside.
Many outdoor cannabis growers eventually upgrade to greenhouse growing. The greenhouse allows more potent crops, higher THC levels and a better terpene profile due to the protection offered by a greenhouse. Whether you are growing with a large commercial budget, or a small greenhouse with just one or two plants, the quality improvements are always important and appreciated. Because greenhouse grown cannabis plants grow in a more sheltered environment the plants are healthier, enjoying more optimized conditions. The plants can grow without damage from extreme cold, storm/hail damage and wind damage. Pests and disease are easy to prevent and deal with in a greenhouse. A greenhouse protects your plants from the worst of the weather, hail and torrential rain. Greenhouses protect your plants from cold weather, creating a warmer environment where your buds can ripen and mature under conditions which are often far superior to outdoor weather.
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.
The recent explosion in ‘growing your own’ cannabis includes the rapidly growing community of greenhouse growers. For many people, growing cannabis seeds in a greenhouse is simpler than creating an indoor grow room. Greenhouse growers find it easier than growing cannabis seeds outdoors.
Even in warm climates, many greenhouse growers supplement the natural light with additional light on cloudy days. These days LED grow lights can be used to provide additional illumination which can be automatically switched on when ambient daylight (PPFD) levels drop too low. Growers in cool climates, such as Scandinavia may prefer to use supplemental HPS lighting which offers both light and heat to the plants. Supplemental lights also allow you to extend the natural sunlight hours. This would allow you to grow autoflower seeds in a greenhouse and have 18-20 hours of daily light. Artificial light would be used to give the autoflower plants their preferred 20 hours of daily light with optimized yields and quality.
Growing cannabis seeds in a greenhouse with artificial lighting
As a result, a greenhouse allows you to grow larger plants which can start earlier and finish later than would be possible growing outdoors without a greenhouse. Many growers of photoperiod feminized seeds routinely harvest several hundred grams, or more, of dried buds from a single plant. Plants can easily reach 2-3 metres tall and just as wide. A greenhouse also protects your plants from the autumn/winter storms. This can allow the greenhouse grower to grow a broader range of later blooming cannabis seeds than is possible outdoors.
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.
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.
How do I get rid of excessive greenhouse humidity?
Feminized seed varieties grow very well in greenhouses. Often, they will grow vegatively until they sense the shortening days, and will start to show first signs of bloom around August, depending on your variety. In the northern hemisphere feminized seeds are often grown from around April to October in a 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 cannabis seed varieties started earlier in the season than they could outdoors. This allows the growing season in a greenhouse to start earlier. Your greenhouse will therefore 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.