can you reuse soil for weed

How To Save Money By Reusing Old Soil

Reusing old soil can save you money and improve overall soil quality. Rehabilitating old soil for reuse when potting or potting-on can have a number of advantages. Learn more about them here.



Unless there has been a disease or invasion of some kind, there is no need to buy new soil every time you want to pot a cannabis plant or repot existing plants. Simply reuse the old stuff. Revitalising and reusing old soil is easy and a great money saver.

Marijuana is a notorious glutton for nutrients of all kinds; nitrogen-hungry during vegetation and calcium and magnesium-demanding during flowering, cannabis will always leave soil depleted. With that said, there are numerous benefits cannabis provides as well; the roots fluff out and the overall soil structure is improved upon. Such is one of the many upsides to growing cannabis.


By keeping soil healthy to begin with, you can prevent the need for its radical rehabilitation prior to reusing. Regular fertilising, composting, and mulching of potted plants with ensure healthy soil at every stage of its life. When well-cared-for soil maintains its health, friability, water penetration and retention, it needs little modification when reused.

Companion planting also helps keep soil healthy, vital, and disease-free. When doing this, however, it’s advisable to plant in a bigger pot than necessary to allow room for companion plants to grow. A simple alfalfa, clover, and marigold mix will provide manifold benefits to plant and soil health.


Uncared for and stressed soils will require amending prior to reuse. The soil may become hydrophobic, completely exhausted of nutrients and minerals, or with a collapsed structure. Soil that has been left to bake in the sun will certainly be leached of nutrients and will need to be modified.


If your soil was invaded by a pathogen or is quite unhealthy for whatever reason, the best thing to do is simply put the soil in a bag and discard. Mixing it into garden beds or working it into compost could spread the pathogen to your whole garden. Sometimes, diseases can linger in soil even after you think they’ve left. This is true for several species of mite, fungus, gnat, and rot. Reusing the soil will certainly infect the new occupant. Be sure to wash your hands before touching healthy soil and plants. Wash the pots as well in warm, soapy water to ensure the vector has been scrubbed away.


Pasteurising old soil is a way to get rid of a number of unfriendlies. Grass and weed seeds, insect eggs, and fungal spores can all be killed by putting the old soil in a black garbage bag, then leaving it to bake in the sun for an afternoon. The heat will pasteurise the soil to be ready for use. It will also kill most of the friendly biota, so you are committed to soil-amending once you decide to pasteurise. Bake in the sun before amending so you don’t kill all the friendlies you add.


Before reusing soil, it must have its texture and fertility improved.

The quickest route to healthier soil is to add 50:50 new potting mix to the old soil. Commercial potting mixes have the disadvantage of drying out quickly and they tend to be compact and have poor structure. They can be expensive, especially if you have a few pots to fill. They do, however, have the advantage of being an instantaneous solve to poor-quality soil and take little effort.

Depending on your outlook towards organic soil structure, you might not like the idea of wetting agents and crystals, slow-release industrially-sourced fertilisers, or hormone enhancements. Perhaps a more hands-on approach to the mystic potion for bigger buds is what you prefer. These ingredient guidelines will ensure you make a rich and well-draining, life-enhancing soil.

Adding compost is the most natural solution to improving soil. A 30:70 mix of compost will provide much needed nutrients and structure to depleted soil. If you are not a composter, there are commercial composts available.

  1. If you would rather make your own organic soil, try this recipe: Volume for volume, add presoaked coco coir, coarse sphagnum moss, or peat moss to the depleted soil.
  2. Add vermiculite, perlite, or course sand until friable. Perlite increases the surface area for friendly bacteria particularly well.
  3. Add compost, bat guano, worm castings, blood and bone, or old mushroom compost to provide essential nutrients.
  4. Add crushed rock dust, dolomite, epsom salts, and molasses to provide a range of vitamins and minerals.
  5. Adding a splash of microorganisms to any soil mix is beneficial. Burgeoning colonies of beneficial root bacteria make plants hardy in the face of weather and disease, pests, and poor pH. They also help decompose old roots into beneficial compounds for new plant growth.
  6. Alternatively, old soil can be reused in other ways:
  • Add it to compost
  • Dig it into garden beds
  • Fill holes and divots in your yard
  • Add to the bottom of planting holes

Building higher-quality soil with organic matter reduces plant stress, improves disease resistance, and saves you money. Well-structured soil retains water, yet drains well and promotes a healthy root zone. This optimises healthy growth for the life of the plant. Add slow-release fertiliser pellets or water monthly with a liquid fertiliser like fish or seaweed emulsion. Regular maintenance means the soil will need less attention next time it is reused.

Improving old soil and then reusing it to plant or pot-up can save money and provide myriad benefits for the cannabis grower.

Cannabis Grow Mediums: Are They Reusable?

Thursday October 17, 2019

Y ou’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.

Tips for Reusing Different Grow Mediums

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.

However, reusing grow media is not as simple as fluffing it 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.

Reusing Soil in Cannabis Grows

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 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.

How to Reuse Coco Coir

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.

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 percent 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, Perlite, Clay Pebbles

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.

You’ve put a lot of time and effort into growing the best marijuana and you’re ready to do it again. You can reuse lights, vents, pots – and even your grow medium if you treat it right. We’ll discuss how to reuse different grow mediums and get you growing your next crop fast.