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Growing Cannabis in Raised Garden Beds

Over the last few years in the United States, public perception of the use of marijuana for recreational and medicinal purposes has softened dramatically, accompanied by varying degrees of emerging legality. As of May 2017, federal law still prohibits the possession, use, sale and cultivation of marijuana; however, it also provisions the allowance of a state to individually mandate its own laws regarding recreational and medicinal use, so long as there is a regulatory system in place.

For instance, California has legalized both recreational and medicinal use, whereas Florida only allows for medical use. We encourage everyone to seek and fully understand the laws and regulations regarding marijuana in their state.

How to Grow Cannabis in Gardens

There are more ways than one to skin a cat, just as there are methods to cultivate marijuana. Indoor cultivators rely on lighting methods to induce and control the different stages of growth, from seedling to flowering to harvest time. This approach certainly has its advantages, especially in regions that receive little sunlight. Some, however, may find the purchase of costly specialty bulbs and higher electricity bills to be a deterrent. Those pursuing a more organic and inexpensive growing method might consider outdoor cultivation.

Cultivating Cannabis in Raised Beds

Enter raised bed square foot gardening, a method celebrated by those who enjoy its simplicity, structure and economy. By dividing a raised bed gardening space into square-foot planting sections, gardeners can create small but intensive vegetable gardens. In contrast to row gardening, where gardeners leave walking paths between rows of plants to access them, raised bed square foot gardening employs area planting within the sections mentioned above. Rows are not needed, since properly designed raised garden beds always have a dimension of 4ft or less, providing gardeners arm’s length access to all plants from one side of the bed or another.  

Novices and experts alike have enjoyed successful yields of all types of vegetables and herbs using the raised bed square foot gardening method and can certainly do the same with marijuana. Consider the following advantages of raised bed square foot gardening when planning your outdoor marijuana grow:

Can You Grow Marijuana in Raised Garden Beds

Ideal Soil Conditions

A strong, healthy marijuana plant requires plenty of nutrients throughout its lifetime, namely nitrogen (N), phosphorous (P) and potassium (K). Unfortunately, the soils found in our backyards tend to be deficient in one or more of these nutrients and can be difficult to work with. With a raised garden bed, you are not limited to local soil conditions. A soil recipe high in nutrients will go a long way in ensuring the success of your plants. Pre-mixed, nutrient rich soil blends are widely available at home and garden stores, however when selecting/creating your growing medium consider the following ingredients noted beneath the following ‘PRO TIP’.

PRO TIP: Matthew Sokolowski, Operations Manager at True Plant Science, suggests a soil recipe that comes from TGA Subcool Seeds, a marijuana genetics breeder out of Oregon. It’s full of quality nutrients that will sustain the plant throughout its entire lifespan. Below is a general recipe that can be adapted to the size of your planting space:

(8) 1.5 cubic ft. bags of high quality base soil
• 33 lbs. bag of Worm Castings

• 2.5 lbs. Fish Bone Meal

• 5 lbs. High Phosphorus Bat Guano

• 5 lbs. Blood Meal

• 2.5 lbs. Bone Meal

• 3 cups. Oyster Shell

• (3) cups. Kelp Meal

• (3) cups Alfalfa Meal

• (3/4) cup Epsom Salt

• 1 cup Dolomite Lime

• 2 cups Azomite

• 2 tbsp powdered Humic Acid

Allow a mix like this to break down over 6-10 weeks prior to planting. This mix yields roughly 14 cubic feet.

A quality soil blend, such as the one mentioned above already contains the necessary nutrients to feed marijuana plants. So, the need for fertilizers and pesticides is greatly reduced if not all together eliminated.

Pro tip: The only time that supplemental nutrients may need to be added is during the flowering cycle, as the plant consumes much more Phosphorous and Potassium than it does Nitrogen. Compost teas would be a good option for adding organic nutrients into the soil as needed. A good flowering tea should consist of Seabird Guano, worm castings, Indonesian Bat Guano (or similar high phosphorous guano), kelp and molasses.

Structure and Spacing

Marijuana plants tend to adapt to the space they are given, but generally grow well in 4-6 gallons of soil. Employing the square foot gardening method in a typical 8-inch-tall raised bed will create equal square foot sections of .667 cubic feet, or about 5 gallons — ideal for one marijuana plant per section.

This intensive spacing system is advantageous when you have limited room to work with. Taking this plant spacing method and expanding it to a common size garden, you could grow 16 marijuana plants in a 4ft x 4ft raised garden bed. (1 plant per square foot = 4 plants across and 4 plants deep).

Marijuana Strain Considerations

There are two primary strains of marijuana, Sativa and Indica. Often they are cross bred but each has growing characteristics to consider. Sativa strains are more prone to growing up/elongating than Indica strains do, making them the a more ideal marijuana strain for 1 square foot plant spacing.

Indica strains tend to grow more bushy or outward. Raised bed square foot gardening is not limited to one square foot spacing as a maximum though. You can grow 1 plant per 2 square feet to accommodate wider growth. Plant spacing as such would allow for 8 plants in a 4x4 raised garden bed.

Despite the common characteristics of Sativa or Indica strains, most any strain can be cultivated in a smaller space with the right kind of plant training techniques and proper trimming maintenance.
Raised Garden Bed Marijuana Plant Spacing 2
Leaf Icon Credit: Nikita Golubev via Flaticon

PRO TIP: The more room marijuana plants have to grow, the wider and bushier they will become. When kept to a more confined root system, the roots are still able to grow downwards but are restricted laterally, resulting in a more conical plant. Some light plant training may be needed to keep the branches of other plants from entangling and preventing the growth of powdery mildew or other disease.Tomato cages would be useful in this situation.

Improved Drainage and Reduced Watering

A well-composed raised garden bed also enjoys excellent soil drainage. This is key to the health of the root systems of your marijuana plants: excess moisture drains out, allowing the roots to absorb oxygen and thrive. At the same time a raised garden bed improves drainage, planting marijuana intensively in a square foot fashion reduces the overall water needed to sustain your garden.

As plants grow in close proximity, they shade the soil and minimize moisture loss. Ultra-efficient ground level watering systems and spacing guides can be easily adapted to the raised bed structure as well. All this means you’ll need less water less often, minimizing your footprint and conserving resources.  

PRO TIP: Cannabis plants in an outdoor environment will generally require water every 2 to 3 days.The amount of water the plants require and application rate will increase as the plant transitions into the flowering stage. Also consider the climate. A Hot and dry climate will necessitate more water than hot and humid climate.To gauge general watering needs for your marijuana plants, ensure that your garden bed’s soil is moist an inch below the surface. Keep a close eye on the plants early on to get a good idea of your water schedule.

Acknowledgements

A special thank you to Matthew Sokolowski, Operations Manager at TruePlant.com and consultant to multi-licensed, commercial cannabis cultivators out of Washington State, for providing his expert insight and ‘PRO TIPS’ to create this guide.

Bryan Traficante co-founded GardenInMinutes in 2013, turning a passion for home gardening and innovation into a family-owned venture to make starting a quality garden, easier. GardenInMinutes invented the Garden Grid watering system which combines square-foot planting principles with efficient ground-level irrigation. GardenInMinutes also crafts tool-free, modular raised gardens and provides time saving gardening insights on their blog and social media pages. Find Bryan and GardenInMinutes on Facebook, Twitter, and read all of his MOTHER EARTH NEWS posts here.


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