Attached greenhouses : These are usually shaped like a house and attached to the existing wall of a house, garage, shed, or barn. This greenhouse option is made of metal or wood framing with glass, fiberglass, or plastic panels. While they might be slightly less expensive than free-standing greenhouses because one wall is already built, the location of attached models is dictated by the location of the existing structure. Prices vary greatly depending on location, size, and construction materials.
A marijuana greenhouse also puts you in control of two primary factors in successfully growing marijuana plants.
Free-standing greenhouses: From a simple walk-in greenhouse with room for a couple of plants to the massive connected behemoths set up by commercial growers, free-standing greenhouses are what most people picture when they think of a greenhouse. They are apex shaped, like a house, and consist of metal or wood frames and glass, fiberglass, or plastic panels. Many have roof and/or side panels that open to allow for ventilation. This may be the most expensive option, but it also has the most room for plants while still allowing for location flexibility so growers can move it to best capture the sunlight. Inexpensive free-standing models start at less than $100 but they may not be very durable. Sturdier models cost closer to $1,000 and prices go up from there.
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.
If DIY is not your style, think about your budget and how many plants you’ll want to grow then decide how much space you’ll need for plants, climate control, and the rest of your greenhouse setup. Armed with that information, consider the options below.
Buying a cannabis greenhouse.
In this guide, you’ll learn why growing marijuana in a greenhouse can be effective and how to get started.
Whether you want to grow recreational weed or medical marijuana, the best greenhouse may be one that you build yourself. If you have the time and skills (or helpers) to construct your own greenhouse, this route will be the most cost-effective.
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.
Equipment: From irrigation to climate-control systems to exhaust fans, the supply list for a cannabis greenhouse can be long. But once you make an initial investment, most equipment will last season to season. Down the road, don’t be afraid to add things like heating or lighting if your cannabis plants seem to need it.
Knowledge: The most high-tech equipment won’t matter unless you have a thorough foundation in how to grow cannabis. This means understanding when seeds should be sown (generally April), when flowering occurs (eight to 12 weeks typically), and which cannabis strains do best in greenhouses (autoflowering strains such as Purple Punch Auto, Jack Herer, and 8-Ball Kush enjoy a great reputation among cannabis growers).
Size and panel opacity: Aside from type and material, two other greenhouse considerations are size and panel opacity. When deciding on size, think about what strains you might want to grow and how tall they might get. A good general rule of thumb is to get a larger greenhouse than the one you think you’ll need. If you don’t need the extra room for equipment and maneuverability, you can always add more plants. As for panel opacity, clear might seem like the best choices but the sun beating down on your cannabis plants can lead to competition in young plants and hot spots later. Diffuse or semi-diffuse panels provide ample, even light, preventing hot spots, competition, and uneven growth. All that should equal better yields.
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 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.
Cold frames: Cold frames are another affordable choice, though they are small and temporary. While it’s possible to construct a cold frame yourself, you can purchase a solid one for between $80 and $200, depending on the size. Cold frames are generally small boxes that sit on the ground. They are constructed out of wood or plastic frames with plastic or glass panels. Cold frames are normally used as is, with only heat from the sun, especially in warm, dry climates like Southern California. In areas with colder temperatures, consider installing a heating system, also known as a hotbed.
Cannabis cultivation can take place indoors, outdoors, or in a combination of these two places: the greenhouse. A greenhouse can be as small as a tool shed or as large as an industrial building. If you have enough space to accommodate even a small greenhouse, this option may propel your cannabis cultivation to the next level.
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.
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.
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.
The ideal spot for your DIY grow room will be facing the sun. A slightly shaded area is fine, but make sure nothing is keeping the natural light from reaching your greenhouse. The more hours of light, the bigger the yield.
Invest in top-quality soil as this will impact the entire growing process. Photo by: Gina Coleman/Weedmaps.
Growing marijuana in a greenhouse.
Lighting: A greenhouse gives cannabis plants the benefit of natural light without exposure to the harmful environmental stressors of outdoor grows. Using natural sunlight is energy efficient, so you can save money on electricity costs by not using artificial lighting.
The key word when it comes to cannabis growing in a greenhouse is control. Photo by: Damien Robertson/Weedmaps.
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.
When considering greenhouse cultivation, think about how much control you would like to have over your crops. If reliable conditions make growing cannabis a more enjoyable experience for you, then a greenhouse may be the way to go. Also, assess how much elbow grease you want to put into the growing process and if you want to build a structure from the ground up. Finally, evaluate your budget and cultivation goals before you make the decision to grow marijuana in a greenhouse. Whether you choose to grow weed outdoors, indoors, or in a greenhouse, raising plants from seed to harvest can be a rewarding experience.
Whether you’re raising cannabis as a cash crop or just for personal use, you have many options for where and how you grow it. It’s possible to grow pot outdoors, indoors or in a greenhouse or high tunnel.
You will want to be sure to give your cannabis plants adequate amounts of water and fertilizer to ensure steady, strong growth throughout the season. A drip irrigation system can supply these essentials reliably and economically. DripWorks.com has an entire section on the best irrigation products to grow cannabis.
If you live in a climate prone to more clouds than sun, you may want to consider investing in auto-flowering seeds. These will flower in a set time rather than depending on sunlight to spark flowering.
Greenhouse vs. High Tunnel.
In many ways, growing marijuana in a greenhouse or high tunnel offers the best option. An outdoor marijuana greenhouse or high tunnel lets you take advantage of some of nature’s benefits, like abundant sun, without having to kneel to nature’s bad side, like frost, storms and deer, rabbits and other pests.
Many folks in northern latitudes start their seeds indoors in April under grow lights and transfer them to a greenhouse in May. Your own schedule will depend on your climate and growing season, of course.
To help you get on your way, DripWorks is happy to provide you some basic tips on how to grow marijuana in a greenhouse or high tunnel.
Once you have purchased or built your greenhouse or high tunnel, you’ll need to decide where to put it. Generally, a spot with southern exposure is best. This will provide a steady source of growth-inducing sunlight to your plants. You may also want to locate your high tunnel or greenhouse in an inconspicuous spot to deter thieves, vandals and other troublemakers.
Like greenhouses, high tunnels shelter plants from the elements. They differ from greenhouses, however, in that they are more passive. Generally, greenhouses provide heat and ventilation through electrical systems, while high tunnels rely on passive ventilation systems for moving air and on the sun for providing warmth.
Plants will usually begin to flower around the summer solstice, the longest day of the year. Flowering will continue for two or three months till they are ready for harvest.
Growing Marijuana in a High Tunnel or Greenhouse.
You can start with marijuana seeds or clones. Whichever you choose, pick the highest-quality stock you can find. This is no place to pinch pennies. Dealing with a reputable company and getting top-notch genetics will help ensure a bountiful crop that’s high in quality as well as quantity.
Of course, that means high tunnels cost significantly less than greenhouses. How much less depends on the options you are looking for. A variety of high tunnel greenhouse kits and traditional greenhouse kits are available for purchase. If you are handy and looking to save, you can also assemble your own high tunnel or greenhouse with some basic materials.
Generally, two basic options are available for growing your pot plants. You can grow each marijuana plant separately in its own container, or you can put the plants in the ground. Using containers will make the plants easier to work with and to move if you want to transplant them.
First, let’s get some terminology issues out of the way. Greenhouses and high tunnels are similar but not exactly the same.
Consider Your Location.
We hope this basic greenhouse marijuana growing guide has been helpful. If you have any questions, feel free to call the irrigation experts at DripWorks toll-free for advice you can trust.
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.
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.
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:
Considerations When Growing Cannabis in a 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.
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.
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.
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.
One to two weeks before the harvest, consider bringing the humidity levels down as much as possible in the 30-40% range.
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’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.
Ventilating the Cannabis Greenhouse.
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.
Too often novice growers handle the seed too much when they are trying to germinate which can accidently 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!