Cannabis Grow Mediums: Are They Reusable?

You’ve put a lot of time and effort into growing the best marijuana in the past and you’re ready to do it again. Besides, now that you have all the supplies (including plants if you take clones or harvest seeds), the monetary investment should be minimal. You can reuse lights, vents, pots – and even your grow medium if you treat it right. Today, we’ll discuss how to reuse different grow mediums to save you time and money, and get you growing your next crop fast.

Grow medium refers to whatever it is a plant grows from. Different types of grow media include soil, coco coir, rock wool, grow stones, clay pebbles and perlite. Though some grow mediums are not recommended for reuse (rock wool cubes, for example, become very compact which makes them hard to clean and sanitize between grows), many others most certainly are.

An example of Perlite, a common grow medium, that can be reused. photo credit

However, reusing grow media is not as simple as fluffing it up and starting anew. If you want your next crop to thrive, you must clean and sanitize your grow medium, and amend as necessary. Here are a few tips to keep in mind.

Just as you must clean and sanitize your grow room between cycles, you must clean and sanitize your soil as well. Cleaning the soil rids it of residual nutrients and salts and helps you better gauge your next crop’s nutrient needs. Cleaning also removes debris like roots and fallen leaves so that new roots can grow without restriction. Sanitization, on the other hand, kills pathogens and pests (and their eggs).

Begin by flushing residual nutrients out of the soil using copious amounts of water (and a nutrient flush solution if possible) to remove minerals from the soil. Repeat the process two to three times ideally. If you have had a pest problem in the past, rinse with boiling water a few times to help kill them off and if you had mildew in your last crop, add an antifungal to your water, as well.

Remember, reused soil is not only flushed of contaminants, it is also free of all nutrients. Before using your soil again, amend it with things like compost, worm castings and peat moss.

After a thorough rinse, set your soil out in the sun to kill off any diseased spores. Continue to remove plant matter at this point to improve your soil’s consistency. Soil should sit for around 10 days before being used again, more if possible.

Coco coir, made from coconut fiber, is an excellent cannabis grow medium for many reasons – it is sustainable, nearly impossible to overwater, boasts the perfect pH balance, and is highly reusable in both soil and hydroponic cannabis grows. But, like soil, it must be processed before reuse. 

The first step in reusing coco coir is to remove any excess plant matter from the previous crop.

Large roots and stems can be removed by hand but smaller roots are best addressed with a special enzyme solution designed to break down roots and improve their bioavailability for future root systems. Thoroughly removing all old roots further ensures that future systems have the room they need to expand and thrive.

Coco coir is an excellent, sustainable option for a grow medium that can be reused. photo credit

Next, wash the coco with distilled water to rinse away dead roots and residual salts that can block nutrient absorption. If necessary, you can sterilize your coco at this point using a 35% hydrogen peroxide solution (remember to rinse thoroughly if you do, though). This step is only recommended if there is risk of contamination, however, as non-sterile coco likely contains beneficial bacteria that you won’t want to lose. Add fresh coco coir to your reused mix as needed to add volume and extend its shelf life.

Grow stones are made from recycled glass, perlite from volcanic glass, and clay pebbles from, well, clay. Though all of these products are made from different materials, their reuse procedure is the same. Begin by removing all dead plant matter with an enzyme wash and your hands. If old root systems are especially large, soak the medium for 30 minutes, break up the root system, then repeat as necessary. 

After roots are removed and the medium thoroughly rinsed, place in the sun to dry for two to three days. This resting period is necessary to keep the medium sterile.

Investing in your own cannabis grow is a big deal. You need lights, pots, ventilation systems, seeds (or clones) and some type of grow media. After gathering your long list of essential growing supplies, cultivating your first crop of cannabis, and harvesting and curing it to perfection, it’s time to reap the benefit of your hard work…and then do it all over again for another harvest in about three to six months.

Do you have tips for reusing cannabis grow mediums? Share them in the comments below.

Photo Credit: Cannabis Tours (license)