Growing Cannabis/ Marijuana in a Greenhouse

Considerations When Growing Cannabss in a Greenhouse

Considerations When Growing Cannabss in a Greenhouse

So you are growing cannabis in a greenhouse. Most of this information is nothing new unless you are new to cultivating cannabis.  Here are a few recommendation to stay on top of during your cannabis growing adventure. 

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Monitor the Temperature and Humidity in the Greenhouse

Humidity and temperature affect each other.  When it is warmer, warm air hold more water than cold air.  For cannabis to grow nicely the temperature and humidity levels need to be in an ideal range for the plants to thrive.  When the plants are in the seedling stage the humidity can be between 70% and 80%.  Some growers will tell you that seedling and clones prefer the level to be from 65-70% humidity. The high humidity is necessary because the roots are not yet developed, and the plant will take in water through its leaves.

Once the plant is in the vegetative stage, the humidity should be between 40% and 70%.  The humidity needs to be lowered by 5% each week. The temperature can also be increased a bit because the roots are now absorbing more water, and evaporation is occurring through the leaves which cools the plant.

Once the plant is flowering, the humidly needs to be lowered to 40-50%. This is considered critical by some growers. At this time you may lower the ambient temperature. With the lights on a good temperature range is 68 to 78.8 degrees Fahrenheit.  

One to two weeks before the harvest, consider  bringing the humidity levels down as much as possible in the 30-40% range.

How doe you monitor the humidity and temperature? Purchase a hygrometer and a thermometer. A digital unit with memory showing you the maximum and minimum values from the past is important. Greenhouse Plastic Questions? 6 mil,  SolaWrap? Let us help!

Cannabis in a SolaWrap Greenhouse



Ventilating the  Cannabis Greenhouse

It's no surprise that heat from the lights will raise up the greenhouse temperatures to dangerous levels if you don't have proper ventilation. In addition you will need proper inlet air coming into the greenhouse. One way to accomplish this is with one fan bringing air into the greenhouse, and one sending the air out of the greenhouse.  The total airflow into the greenhouse affects the humidity.

Overwatering in the greenhouse

It's tempting as a new cannabis grower to overwater your plants. Plants will droop and can drown and die in water. One simple way to know if the plants are dry is to stick your finder in the top inch of the soil and see if the soil sticks to your finger.  If it does not stick, then it's time to water.

Ample Light

As a new grower, don't try to grow without sufficient light. Did you know that the plant yield is in direct proportion to the amount of light it receives? There are three types of lights:

  1. LED Grow Lights
  2. High Intensity Discharge (HID) Grow Lights
  3. Fluorescent Grow Lights


pH Level for your cannabis in your greenhouse

As a grower it is important to monitor the pH levels of the water you use to feed your plants. pH is the measure of how "acidic" or "alkaline" something is on a scale off 1 to 14.  "7" is considered neutral.  Small sickly buds may be the result in part of improper pH levels.  A cannabis grower can measure the pH of water sample using a special p tester drops or a digital pH pen.  When the pH is within the correct range, the plants can get the most out of all the nutrients, and their buds will reflect it. If the pH at the roots is too high or low, the plant can't properly absorb the proper nutrients.

Don't Harvest the Cannabis Too Early

It has been said that new cultivators are apt to harvest the crop too early. If you harvest too early, when the trichomes are still clear, the THC will not be as strong.  Ideally one should wait until a more milky color has filled half of the trichome heads.

 Be Gentle with the Seeds

Too often novice growers handle the seed too much when they are trying to germinate which can accidentally kill them before they have the opportunity to sprout.  Seeds can take as long as 10 days to sprout. Patience in this case is a virtue!


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