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How Cover Crops Can Help Your Cannabis Garden

Cover crops are starting to become more popular with cannabis growers because of the array of benefits they can offer to your soil and your garden.

So what exactly are they?

Cover crops are any plant used to improve and protect the soil for the next farming season, as well as plants grown alongside your cannabis plants to fend off unwanted pests. In the fallow season, instead of leaving your garden soil bare over the winter, this age-old organic farming technique adds organic matter, both above and below the surface, helping to improve the soil structure for future use.

Cover crops help the soil hold onto water and nutrients, and prevent erosion and soil compaction. They can also be used to help fend off, or trap, predatory bugs.

Common Types of Cover Crops Used

If you are growing outdoors in a farm setting, most people will go for seasonal cover crops.

For example, when heading into the winter months, in order to get your soil ready for the spring, you might want to use a good mix of cereal crops (such as rye and oats) combined with legumes (e.g. crimson clover and alfalfa grass). As these take hold over the winter and finish growing at the beginning of spring, farmers will then “lay” the crop down, and using a stamping tool, cover the crops with an effective weed barrier to help them decompose. This enriches the soil with nutrients and prevents unwanted ‘weeds’ from taking hold.

You can also use cover crops, such as buckwheat, sorghum and millet, in the summer months. These provide all of the same benefits, just in a different season.

Cover Crops Prevent Soil Compaction

When you plant cover crops in your garden or pots, multiple things will occur during their growth. One of the biggest advantages is correcting or preventing compacted soil and clay.

Legumes (peas, beans, vetch, and clovers) and brassica’s (broccoli, kale and cauliflower) have deep penetrating roots. This allows them to reach the deeper parts of the soil where compaction can happen. If you have layers of dense clay, these roots will penetrate those layers, breaking them up and allowing the beneficial microbes to finally enter and help create a more loam soil.

Cover Crops Support Living Soil

Your cover crops will serve other purposes as well. When you plant a cereal such as rye or wheat, and you stamp them down before they start to seed, you’re giving the soil food web a source of nutrition to consume and multiply themselves. This allows beneficial fungi to take hold, which will help support the root structure of your main crops. This will also allow bacteria to multiply, helping in the breakdown process of the organic matter, making more of those nutrients available for your main crops to feed on.

Nitrogen-Fixing Cover Crops

There are cover crops that are known for pulling nitrogen out of the air, such as alfalfa and vetch. They will draw nitrogen from the air and store it in their roots, leaves and stems via nitrogen-fixing bacteria that live on their roots. Then, when you stamp them down, they release that nitrogen into the soil, getting the soil ready for the main crops. These processes happen with your indoor grows as well. Just on a smaller scale and can be used as added food for the dinner table.

Improving and Maintaining Soil Structure

Another reason to consider cover crops, especially for outdoor farmers, is the fact they will help with the soil structure. They have been proven to help soil hold onto water and nutrients better. The reason this happens is due to the proximity of the plants with each other. The root structure starts to become dense, and those roots will hold onto water until it’s time to stamp them down. That water will then be slowly released back into the soil, causing any dry spots to go away.

As the crops break down, they house nutrients that they have pulled from the soil, as well as the air and rain. Then, once stamped down, they will release those nutrients back into the soil, where fungus and bacteria break them down further, making them available to the main crops you’re planning on using. This is quite beneficial to soil growers that are growing in pots since it will not only prevent compaction but will also limit the need for constant amending of the soil. This will help with the major issues with soil – drainage and runoff.

Fixing Soil Erosion and Hydrophobic Conditions

For farmers or indoor growers with soil issues, where your soil has either become hydrophobic (won’t retain water), or you are starting to notice erosion happening, cover crops are the only solution.

This is where summer crops can come into play. They don’t require a lot of water to grow. Yet, as they start to take hold, developing their leaves and roots, you’ll see the same thing happen as with the winter crops. As the roots start to develop, they hold onto water, rehydrating the damaged soil. Then, if you have deep penetrating roots mixed in, they will draw nutrients from the deeper parts of the soil and hold onto those nutrients.

You also have the canopy. As they grow, they again start to hold onto nitrogen, which will also help nurture the health of the soil. And for extremely bad areas, you can combine this with natural fertilisers, such as manures, meals (bone meal, blood meal, feather meal, etc…) and mixes.

Right before the crop goes to seed, again, stamp them down and cover them to start the breakdown process. Since you have created a dense root structure, and now a canopy that was green and lush, you will start to see the effects of erosion reverse. You will even start to see that the soil will hold water for much longer, not wanting to let it go. This helps prevent land from breaking apart and getting washed out. And the continual efforts will help your main crops start to grow bigger and more vibrant each year you do this.

Trap Cropping

Trap cropping is a newer way of utilising cover crops. With this, you are selecting crops that you aren’t going to use for anything except trapping insects that you want to keep out of your main crops. You use a similar crop to the main crop you are trying to protect, preferably something the insects like to chew on more. You then can use other organic methods to rid them of your garden via the use of predatory insects.

A good example of this would be with the planting of Roma tomatoes. One of your biggest enemies for these tomatoes is the horned worm. So, to combat this, you create a separate garden, no closer than 10 feet from your main garden, and you plant cherry tomatoes. The evidence is starting to show, the worms will attack the cherry tomatoes first, allowing you to either pick them off, or use a predatory insect like praying mantis’ or beneficial nematodes to keep them quelled.

There are so many ways of utilising these crops to trap other insects and keep them out of your main garden. This technique gives you and your crops a fighting chance, and will also start attracting other beneficial life that will eat the pests, keeping your farm nice and healthy.

The Drawbacks of Cover Crops

As with everything, you don’t get a whole host of benefits without some drawbacks. There aren’t many downsides with cover crops, but they are worth talking about and so you can find ways to prevent certain issues from happening.

The main drawback would be that you will be attracting more and more non-beneficial insects and microbes into your garden. The best way around this, is to plan ahead. Make sure you don’t have too many of them in the first place, or utilise nematodes and bacteria that will attack the non-beneficials, helping to rid you of them before planting. Utilising trap crops will help as well. They will gravitate towards those crops more, giving you a greater chance of getting rid of them.

The next thing you need to look at, are invasive areas. Some cover crops are great in certain areas but can be invasive weeds in other areas. You will need to do research there, to make sure you’re not introducing something harmful to your environment. This is less prevalent in indoor grows since your crops are in a controlled environment.

If you have weeds that will outcompete your current cover crops, you can start off by covering the area with a layer paper or cardboard (cardboard is more manageable), then a layer of compost, and finally covering with a weed barrier for a good two or three weeks. Then you can start planting the cover crops, essentially burying those weeds, and suffocating them.

The final drawback would be, having to buy seed all the time. There is a very simple way around this, called cyclical planting. But this is more for the larger farms out there. For cyclical planting, you section your plots into two or three groups. One section is where you will be growing your main crops. The next section could be your cover crops that you will stamp down before they go to seed, this will feed your soil. Then, the third plot would be where you grow cover crops to seed, and harvest the seeds before they fall. The last two can be done together. Where you allow the cover crops to go to seed, you can return the rest of the material back to that plot as a mulch.

Conclusion

Cover crops are a fascinating addition to the farm. They can add a lot of benefits to the soil, whether you are an indoor or an outdoor grower. Cover crops will add nutrient availability to the soil, at the same time helping the soil hold onto water. They will help with erosion and compaction issues, eliminating the need for tilling. They will even add biological and physical properties to the soil as well. That’s not to say that cover crops don’t come with issues, but that the issues can be easily taken care of with some simple planning and research.

Cultivation information, and media is given for those of our clients who live in countries where cannabis cultivation is decriminalised or legal, or to those that operate within a licensed model. We encourage all readers to be aware of their local laws and to ensure they do not break them.

Chris Staniszewski