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What Is The Best Growing Medium For Cannabis?

What is the best medium to use for your cannabis grow operation? Find out the pros and cons of growing cannabis in soil, coco, rockwool, and hydroponics.

Cannabis cultivators can choose from various growing media and techniques to achieve a successful harvest. Do you want to grow in soil, coco, or go with an elaborate hydroponic setup? What are the pros and cons of each, and which one should you choose? Since choosing the right growing medium is an important step on the path to growing great cannabis, we thought we’d provide a guide to make the process easier.

HOW TO CHOOSE THE RIGHT GROWING MEDIUM FOR CANNABIS

A growing medium is where your cannabis plants develop their root system. Many growers keep it simple with pots of soil, but you can also use coco coir, perlite, rockwool, or go for a fully fledged hydroponic setup.

What’s important to know is that there really is no “best” way to grow. Each medium has its pros and cons, though you may prefer one over the other based on your preferences and resources. As long as the roots of your plants can access water, nutrients, and oxygen, they will grow.

Now, let’s take a look at the differences between each growing medium.

SOIL/COMPOST

Difficulty: Easy
Cost: Low

Growing in soil is the simplest way to get some nice weed plants going, but don’t think that means soil produces poorer results than other methods. Far from it! Many growers say that soil enriched with high-quality compost grows them the best-tasting weed, even if yields aren’t quite as good as in coco or hydro.

The main advantage of soil is that it is forgiving and beginner-friendly, and you can still crop cannabis of top-notch quality. Soil is also widely available and relatively inexpensive.

ADVANTAGES DISADVANTAGES
Seeds, a pot, some soil, and some love are all you need. Good for beginners! Comparatively higher risk of pest infestations, mould, and fungus.
pH fluctuations are typically less severe or problematic. Plants produce lower yields compared to other growing methods.
Many commercial soils contain enough nutrients for 3–4 weeks of growth. Plants grow slower, so it can take longer to spot growing problems.
Soil is the method of choice when you want to grow naturally and organically. Not all soils are optimal for cannabis.
Growing in soil can give you the best-tasting cannabis.
ADVANTAGES DISADVANTAGES
Seeds, a pot, some soil, and some love are all you need. Good for beginners! Comparatively higher risk of pest infestations, mould, and fungus.
pH fluctuations are typically less severe or problematic. Plants produce lower yields compared to other growing methods.
Many commercial soils contain enough nutrients for 3–4 weeks of growth. Plants grow slower, so it can take longer to spot growing problems.
Soil is the method of choice when you want to grow naturally and organically. Not all soils are optimal for cannabis.
Growing in soil can give you the best-tasting cannabis.

COCO/PERLITE

Difficulty: Medium
Cost: Low to medium

Growing in a mix of coco and perlite provides the advantages of a hydroponic grow and the ease of a soil grow.

As a coco/perlite mix does not contain any nutrients, you are responsible for giving hydroponic nutrients from the start. The big advantage here is that you have full control, and your plants will grow as fast as in hydro. Downside: Just as with hydroponics, you will have to closely watch your pH levels. It’s also less forgiving of mistakes than soil.

ADVANTAGES DISADVANTAGES
You can grow big plants with very good yields! You need to administer nutrients from the start.
You have full control over nutrient and pH levels. You need to watch pH and EC levels carefully: A small mistake can quickly lead to problems.
No special equipment needed. Not as widely available as soil. You may need to order coco online.
Coco is a renewable resource.
Coco/perlite is (almost) as easy as growing in soil.
ADVANTAGES DISADVANTAGES
You can grow big plants with very good yields! You need to administer nutrients from the start.
You have full control over nutrient and pH levels. You need to watch pH and EC levels carefully: A small mistake can quickly lead to problems.
No special equipment needed. Not as widely available as soil. You may need to order coco online.
Coco is a renewable resource.
Coco/perlite is (almost) as easy as growing in soil.

ROCKWOOL

Difficulty: Medium/high
Cost: Medium

Previously used only in construction, where it experiences widespread use as insulation material, rockwool has become a top medium for horticulture. Just like perlite and coco, it is a so-called “inert” growing medium that doesn’t have any nutrients in it. Rockwool is made from cotton candy-like fibre spun from basalt rock and has excellent moisture-retention abilities. You can find rockwool for growing in a variety of shapes and sizes, from smaller blocks and cubes to large slabs.

Rockwool is most often used in hydroponics. The roots of the plants receive support from the rockwool as drippers provide water and nutrients.

ADVANTAGES DISADVANTAGES
Rockwool supports a sterile grow with little risk of pests, disease, and infestation. You need to give nutrients from the start.
Like hydroponics or coco, you have full control over pH and nutrient levels. You need to watch pH and nutrient levels.
You can germinate cannabis seeds in rockwool cubes. When transplanting, you can just keep the seedling safely in its cube. You can’t grow organically.
You need to soak rockwool in low-pH water before use.
Rockwool is not natural and doesn’t biodegrade. Reusing rockwool is not recommended.
ADVANTAGES DISADVANTAGES
Rockwool supports a sterile grow with little risk of pests, disease, and infestation. You need to give nutrients from the start.
Like hydroponics or coco, you have full control over pH and nutrient levels. You need to watch pH and nutrient levels.
You can germinate cannabis seeds in rockwool cubes. When transplanting, you can just keep the seedling safely in its cube. You can’t grow organically.
You need to soak rockwool in low-pH water before use.
Rockwool is not natural and doesn’t biodegrade. Reusing rockwool is not recommended.

HYDROPONICS

Difficulty: Medium/high
Cost: High

There are various types of hydroponic setups used for growing cannabis. Some systems hold plants in pots filled with a hydroponic growing medium such as clay pebbles, perlite, or rockwool, with drippers dispensing water and nutrients to your cannabis.

You can also find setups that do not use a solid growing medium at all. In these systems, plants are suspended above a tank, with the roots reaching down into the water/nutrient solution. Some systems may use a combination of these, with the plants in a solid medium and the roots suspended in a tank. Simple dripper setups are relatively affordable, while more elaborate systems that make use of pumps and other equipment can be quite expensive.

ADVANTAGES DISADVANTAGES
Your plants will grow large and fast for maximum yields. You need to maintain the correct pH and nutrient levels.
You have control over the pH and nutrient levels of your cannabis. You need to empty your tank and clean your system once in a while.
You don’t need to feed as much (if you have a recirculating system). You need to give hydroponic nutrients from the start.
Low risk of pests and soil-based diseases. A hydroponic setup will cost more than some pots and a bag of soil.
Your weed may not taste as “natural”.
ADVANTAGES DISADVANTAGES
Your plants will grow large and fast for maximum yields. You need to maintain the correct pH and nutrient levels.
You have control over the pH and nutrient levels of your cannabis. You need to empty your tank and clean your system once in a while.
You don’t need to feed as much (if you have a recirculating system). You need to give hydroponic nutrients from the start.
Low risk of pests and soil-based diseases. A hydroponic setup will cost more than some pots and a bag of soil.
Your weed may not taste as “natural”.

WHAT IS THE BEST GROWING MEDIUM?

In conclusion, there is really no “best” growing medium for your cannabis—each has its own strengths and weaknesses. Many times, it will come down to cost, in which case soil is still the reigning champion.

  • Consider growing in soil/compost if you’re just starting out or simply want to go the most natural route.
  • Consider growing in coco/perlite if you’re already confident growing in soil and feel that you want to upgrade. Growing in coco has the advantage of providing almost all the benefits of hydro, but it’s still essentially as easy as growing in soil.
  • Consider using a hydroponic system if you want the fastest growth, biggest yields, and full control over most aspects of your grow. With many hydroponic setups, you are free to use an inert growing medium of your choice (clay pebbles, perlite, rockwool, etc.), so there is plenty of room for some horticultural experimentation.

HOW TO GROW CANNABIS USING SOIL, COCO, HYDRO, OR ROCKWOOL: FURTHER READING

Are you still on the fence about which growing medium to choose? Here are some articles we recommend reading:

• The Home Grower’s Guide To The Best Soil For Cannabis Choosing The Best Soil For Cannabis: A Home Grower’s Guide.

• Growing Cannabis With Coco Coir Growing marijuana in coco coir is a fantastic alternative cultivation style.

• Hydroponic Cannabis Growing Guide Hydroponics is a method of cultivating plants, specifically cannabis in this case, in a solution of water and nutrients.

• Rockwool For Hydroponic Marijuana Growing Rockwool is a great medium for growing marijuana.

What's the best growing medium for cannabis? Find out the differences between growing cannabis in soil, coco, rockwool, and hydroponics here.

Hemp growing medium

Hemp mats are ideal for growing microgreens and wheatgrass. They are made of 100% natural hemp fibre, creating a biodegradable soilless growing medium with high water retention. Easy to use with no mess they can be composted after use.

What are Hemp Mats made from?

Hemp mats consist of fully compostable, 100% natural (industrial) hemp fibre. The fibres are intertwined to form strong but light and airy mats. They are a very clean growing medium. Industrial hemp includes all varieties of cannabis cultivated for commercial use – apart from its use as intoxicants or medicines. Industrial hemp is a tall, leafy plant with a strong, fibrous stem. Hemp fibres are the most important raw material of industrial hemp, both in terms of quantity and use. From ancient times to the present, hemp fibres have been and are used to make a variety of products. Historically, they were particularly important for the production of canvas and ropes until well into the 19th century. In 1455 Gutenberg printed the first bible on hemp paper. In 1492, Columbus sailed to America with sails and ropes of hemp.

Microgreens and Wheatgrass

Hemp mats are ideal for growing microgreens and wheatgrass. They have all the advantages of compost without the associated problems of storing and moving a large bag of compost. They are also cleaner if they are to be used in a kitchen. As the microgreens are only on the mats for approx two weeks there is no need for the nutrients in compost – that is provided by the seeds themselves. Matting can be bought as a roll of 15m x 1m or in convenient 1m x 1m lengths. It is made in Holland.
Microgreens are tiny edible plants that are older than a sprout, but younger than a full-grown plant. Microgreens are harvested after the first “true” leaves have developed. They need hemp or soil and light to grow. They are a concentrated nutrient source and packed with beneficial enzymes because of their rapid growth.
Wheatgrass is also a microgreen – the wheat germinates and grows to about 15-20cms before it is cut and juiced. Unlike other microgreens it is grown for juice rather than its physical appearance

What are the best seeds for microgreens?

This depends on the leaf that you want in the end! All viable seed will grow into microgreens – but some are more colourful or have a spicy taste. Beetroot will give you lovely dark leaves while sunflower will give you bulk and a good textured leaf. The brassicas and mustards will give a hot spicy taste whilst peas will give you both that lovely fresh pea taste and attractive tendrils. You could also experiment with making your own mix. You should always use seeds from a reputable source, preferably organic.

What equipment do I need?

Good quality organic seed compost or hemp mats are essential. You will also need trays of some sort – either seed trays or small containers. You might need an additional light source in winter.

Getting started
• Soak the seeds for 6-12 hours. Rinse and drain well.
• Sprinkle the soaked seeds over a tray lined with a pre- soaked hemp mat or compost and press down gently.
• Use more seeds than you would normally to ensure a good crop of leaves.
• Keep mat or compost moist (but not soaking). You should see signs of germination after about 6 days.
• Microgreens are best kept at a steady temperature of about 20°C
• Cut after about two weeks, or when you are happy with your crop!
• Keep the tray in darkness for first 1-3 days depending on the seeds, after that you should place your seeds in sunlight or a well lit place, for approximately 8-10 hours per day.

Tips for perfect microgreens

• Don’t overwater! Too much water means seeds aren’t able to get oxygen to their roots. It also increases the risk of algae or fungus growth.
• Your trays should have good drainage whether you’re using soil or hemp mats.
• Don’t plant seeds too densely together. Roots growth will make water drainage difficult. As microgreens get taller, they can form a canopy if they’re too thick which traps in humidity and heat, which can cause the growth of mold and fungus.
• You might want to consider shading your plants to offer them some protection if they’re getting too much sunlight.
• Always use fresh, top quality seed and quality growing mediums.
• When storing seeds, make sure to seal the package tight. Keep seeds stored in a cool, dark, dry place. Light can damage them, and if they accidentally get too wet or humid they might start to sprout in storage

Health Benefits of Microgreens and Wheatgrass

Microgreens are packed with nutrients. While their nutrient contents vary slightly, most varieties tend to be rich in potassium, iron, zinc, magnesium and copper. Microgreens are also a great source of beneficial plant compounds like antioxidants. Microgreens are also rich in enzymes, which enable them to be more easily digested. What’s more, their nutrient content is concentrated, which means that they often contain higher vitamin, mineral and antioxidant levels than the same quantity of mature greens. Given that microgreens are easy to grow at home, they’re an especially cost-effective way to boost nutrient intake without having to purchase large quantities of vegetables.
Wheatgrass is an excellent source of chlorophyll, vitamin A, vitamin C, and vitamin E. It also contains 98 of 102 elements found in soil, including phosphorus, calcium, iron, magnesium, and potassium as well as essential enzymes and 12 amino acids. Wheatgrass is made up of 70 percent chlorophyll. Just one shot of wheatgrass juice will provide you with the vitamins and minerals of 1kg of leafy green vegetables! Eating vegetables is linked to a lower risk of many diseases. This is likely thanks to the high amounts of vitamins, minerals and beneficial plant compounds they contain.

Ireland’s organic farm and garden specialists