greenhouse weed growing guide

If you’ve ever seen cannabis growing indoors or in a greenhouse then you’ll most likely remember a tightly packed canopy of buds. Cannabis growers call this the Sea of Green Method ( SOG ). The benefit of growing cannabis using a SOG is to accelerate bud development to gain large yields as quickly as possible. This method of growing calls for more plants per square foot and a short vegetative stage. The most popular benefits of a SOG grow include:

When setting up your grow room, consider these tips when setting up your SOG environment:

It’s simple to begin growing in a Sea of Green in just a few simple steps, but first, you’ll want to consider that:

Brief History of the Sea of Green (SOG) Method.

Helpful Tip: You can use specialized grow light software to automatically adjust lighting intensity when transitioning between growth stages.

When the marijuana industry began transitioning to indoor growing, farmers began to increase the density of their grow rooms to use light and space efficiently. Over time, these farmers realized that by growing smaller plants using the SOG method, they could get more harvests while saving on HVAC, water, fertilizer, labor, and other costs.

Photo showing lighting layout for a SOG grow.

The number of plants per square foot should be determined based on how much space you have available. Using the SOG method of cultivation, we generally recommend 1 plant per square foot, with no more than 2 plants per square foot max.

To get your grow room lighting, temperature, humidity, VPD, and CO2 right, use the helpful SOG growing guide below and get started in no time!

When growing plants using SOG you will get bud sites quickly since you don’t need to “top” the plants. The faster the buds form means more harvests you can fit in a year. For cannabis businesses or anyone else whose goals rely on consistent harvests of big yields, SOG is an important method for speeding up your crop cycles for consistently high yields.

Determining How Many Plants Per Square Foot Using a Sea of Green.

Now that you’ve chosen the plants you want to work with, it’s time to start growing with these basic rules-of-thumb:

Close-up photo showing a Sea of Green setup.

When the marijuana industry first moved to indoor growing, farmers began to use artificial light to control flowering times. This meant that they could increase yields and shorten harvest times by growing more plants in a smaller space, a method now known as a Sea of Green. But this was not always a popular method for growing.

Photo of an outdoor cannabis farm in Humboldt.

How to Use the Sea of Green (SOG) Method.

A detailed growing guide for the Sea of Green method.

It seems simple, right? Well, for the most part, it is. The difficulty comes when you need to adjust environmental parameters and genetics to improve flower yields. Luckily, we’ve got the lighting part of the equation dialed in for you:

The traditional way of growing used large marijuana plants, which comes from the outdoor farming methods practiced in Northern California and Humboldt. In the region known as the “Emerald Triangle”, growers had all summer to produce large vegetative cannabis plants before fall came around to flower. Some of these trees could produce upwards of two to three pounds or more.

Helpful Tip: Before starting your own Sea of Green, it’s important to check the local regulations in your region. Some cannabis authorities and governments limit the number of plants you can have. If this is the case, there are other growing methods that will be better suited for high yields with fewer plants than using a SOG.

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.

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.

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.

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.

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.

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.

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.

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.

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.

First, let’s get some terminology issues out of the way. Greenhouses and high tunnels are similar but not exactly the same.

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.

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.

Consider Your Location.

A greenhouse protects your plants from high winds, damaging rain and low temperatures. Insects and pests can be easier to deal with in a greenhouse and less of a nuisance. All these factors are reasons why greenhouses are a great asset for the cannabis grower.

If you get a greenhouse it pays to think carefully about the location. When it comes to security, always think about a location which makes it difficult for neighbours or the public to see/smell your crop. Also consider your local climate. If you are living in a cool climate it pays to locate the greenhouse where it will receive maximum sunlight for as much of the day as possible. If you live in a hot, desert climate you may want to consider locating the greenhouse under some trees which will shade the greenhouse during the hottest hours of the day in mid-summer. Mediterranean greenhouse growers may wish to place their greenhouse in a cooler, northern part of the garden where some shade may be present. Remember that when temperatures reach 40-45ºC the temperatures become damaging.

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.

Feminised cannabis seeds and greenhouses.

Some greenhouse growers even feed their greenhouse cannabis with automatic systems (e.g. AutoPot, Blumat, dripper systems or similar). It’s possible to grow cannabis in soil, coco fibre or any other grow medium in a greenhouse.

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 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.

Sophisticated greenhouse growers have watering systems in place to simplify and even automate water delivery. If the greenhouse is not in an entirely private location then it might benefit from a coat of white shading paint. This is sold in garden centres and used to protect greenhouses from overheating on the hottest summer days. For the cannabis grower this shading paint also stops people seeing what is inside your greenhouse, but green plastic plant mesh and tomato plants have also provided excellent cover for many generations of greenhouse growers.

Greenhouses can be fitted with windows which open in hot weather and close automatically when it cools down again. These allow the hot air to escape quickly. An open door in your greenhouse can allow a cooling breeze to flow through. Greenhouse doors made with panels of fine wire mesh keep insects out but allow air to flow through.

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.

Where to locate your greenhouse?

Greenhouses can be heated if required. This allows you to optimise the greenhouse environment even if you have unexpected frosts or stormy weather. It also allows you to germinate your cannabis seeds earlier than you might do for an outdoor grow. Read all about how to germinate your seeds in our germination guide .

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.

One problem with greenhouse growing is that the temperatures can get very hot in sunny mid-summer weather. High temperatures make it difficult for the plant to grow. Leaves may wilt and the roots can find it difficult to provide sufficient water. This can be a serious problem, especially in a heatwave when temperatures inside the greenhouse can be in excess of 30ºC or even 40ºC. At these temperatures the cannabis plant struggles since conditions are so far from optimum. But the determined greenhouse grower can find ways around these challenges.

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.

Greenhouse cultivation of cannabis seeds. Using pots vs planting directly into the ground.

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.

In a heated greenhouse the seeds can be germinated and planted around March/April, depending on your local weather conditions. This allows an earlier start than is usually possible outdoors. That’s because the greenhouse offers extra protection from the worst of the early season weather.

Some people copy the large legal greenhouse growers in the USA and fit an extraction fan to pump humid stale air out of the greenhouse. This can be combined with a carbon filter to remove any cannabis aroma from the exhausted air.

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.

Greenhouses are available in a wide range of sizes and budgets. The lowest cost ones use a flexible transparent plastic mesh sheet which fits over a small plastic/metal pole frame. These can cost as little as €20 but can only fit a single plant inside. Some greenhouses are designed to be leant against an outside wall of the house. Heat from the house helps keep the greenhouse warm. Greenhouses are also available for people that live in an apartment and have a small balcony. Polycarbonate greenhouses use toughened ‘unbreakable’ transparent plastic panels instead of glass, these are useful if you are worried about safety or have small children. Whatever your budget and space, somewhere there is a greenhouse for you.