How To Grow Hemp In A Greenhouse

With the 2018 Farm Bill in place, the United States gave the signal for farmers to start cultivating hemp (finally!) by removing it from the group of Schedule I Controlled Substances. 

Hemp has been around for hundreds of years due to its versatility and health benefits. Still, because of its similarity to marijuana, hemp was made illegal in 1937 under the Marijuana Tax Act. The 2018 Farm Bill paves the way for hemp to be treated as the agricultural commodity it has always been.

Hemp is usually grown outdoors in fields, but what if the climate, weather, or other agricultural factors get in the way of its proper growth? In that case, learning how to grow hemp in a greenhouse resolves this concern.

Cultivating hemp in a greenhouse is not any different from growing marijuana when it comes to producing large yields and big buds. For example, hemp and marijuana both require a vegetative and flowering stage of development. 

Understanding how to grow hemp in a greenhouse means tackling how you would cultivate the crops without natural daylight. A heated greenhouse requires supplemental lighting. These days, growers have been turning to LED technology, according to a 2021 survey by Cannabis Business Times.


You can grow hemp all year around.

In areas with warmer temperatures, hemp is usually only harvested once per year. It is easier to control the climate with a greenhouse, which means that you can grow hemp all year, and you will likely see multiple harvests.

Depending on environmental factors and allowing natural sunlight in your greenhouse, you can easily transition your hemp plants into vegetation through the winter and flowering through the spring and summer. It is also possible for you to increase your production of CBD per year in a greenhouse by pruning plants in a more prolonged vegetative state before they start to flower.

You have fewer concerns with pests.

Pest management is a significant aspect of growing outdoor field crops. But when you’re growing hemp indoors like a greenhouse, it is much easier to manage pests in this environment. 

Hemp grown in fields is highly susceptible to many different bugs, rodents, and birds. This entails farmers having to use many pesticides, which can be expensive. It can also generally not be healthy for the environment or the outcome of your crops. 

In a greenhouse environment, hemp growers have more control over pest management. Your internal equipment works its magic and benefits the crops while pests that may damage them stay outside. 

Greenhouse hemp growing means fewer pesticides and more control about what enters your greenhouse. However, always be sure to have climate controls set in place to avoid mold and mildew, which occurs from the humidity.


Consider your location.

The most crucial factor to consider before making other decisions is where you will grow your hemp and the positioning of your greenhouses. 

If you plan to start with a few greenhouses, you may need to consider the spacing of your environment or lack thereof. You must place your structure in a location that faces natural sunlight, cutting down on your energy costs and reducing the need for supplementary lighting.

Choose your structure.

There are several greenhouse structures available, so it is in the consumer’s hands to choose the most practical and cost-effective option for an indoor hemp cultivation operation.

These greenhouses are great options for growing hemp:

  • Poly-connected greenhouse 

A poly-connected greenhouse is a versatile choice for almost any crop, including hemp. The structure can easily undergo expansion and is one of the most economical greenhouse options for large-scale hemp growers. It also provides superior condensation control because they utilize gutter vents and other ventilation options that allow for proper airflow.

  • Cold frame greenhouse (also known as a hoop house) 

A cold frame greenhouse is also a cost-effective option for growing hemp all year-round. Hoop houses are an excellent starter greenhouse for beginners. Growers may simply add fans or natural ventilation equipment, making it quite budget-friendly.

Consider blackout curtains.

If you are growing hemp for CBD production, your crops will require stages of total darkness during the flowering stage. Light deprivation curtains, also known as blackout curtains, can penetrate the greenhouse and provide darkness during the flowering stage. 

The hemp plants will require 12 hours of continuous darkness, which allows the crops to start flowering. Make sure that the blackout curtains cover the door, walls, pretty much any access to light– to ensure that no light is entering the greenhouse.

Regarding the benefits of growing hemp in a greenhouse, this is only the tip of the iceberg. The demand for low THC and high CBD products is increasing, and we will likely see more cultivation of hemp in greenhouses in the coming years.


Here are general tips when it comes to how to grow hemp in a greenhouse:

  • Adequate spacing and airflow are vital in greenhouse hemp growth. Ensure that your crops have plenty of space, so much so that they should constantly be moving from the air current.
  • Conduct water and soil testing before applying fertilizer to avoid the over/under fertilization of your crops.
  • Hemp is best suited with well-drained soil that has a pH level between 6 to 7.
  • Use water-soluble greenhouse fertilizer on your crops.
  • Avoid low-grade fertilizer with high sodium content. It may cause stress in your plants, and they may stop absorbing nutrients.
  • Ensure continuous feeding through drip irrigation lines, which is the most effective way to water and fertilize your crops.
  • Apply more nitrogen and potassium during vegetative growth. 
  • Apply more phosphorus and potassium during flowering to the harvest.


Building a hemp greenhouse is only the first step in your journey as an indoor hemp cultivator. It can also be the start of a profitable revenue source for hemp growers everywhere. 

However, if the greenhouse is not set up with the essentials of proper hemp cultivation, it may not yield high-quality and reliable results.

That is why we prioritize helping hemp growers in their cultivation journey through helpful resources on proper environmental controls, heating, cooling, ventilation, and light equipment— to ensure that they have success from the start.

If you are interested in learning more about how to grow hemp in a greenhouse or even hemp in general, we at Zera would love to help. Ready to get growing?