- Weedguru Higher
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Selecting the appropriate growing media to use is an important step in producing a quality cannabis plant. Most of the media used by growers consists of combinations of peat moss, perlite, vermiculite or other organic constituents. Regardless of what a media is composed of, it must provide the basic physical and chemical properties required for plant growth.
When growing marijuana outdoors, soil or a mix of soil and compost is what is used. When growing indoors, a soil or soilless mix can be used, though some growers often prefer to grow hydroponically using different mediums. Marijuana is often called weed and like a weed it will grow in almost anything you can think of. As long as the roots have room to grow, are kept moist and are supplied with oxygen and nutrients the plant will thrive.
Below is a simple explanation of some of the different mediums commonly used.
Soil is a good medium, it is natural ,easy to use and available everywhere. Marijuana soil should compact when you squeeze it and break apart easily when you poke it. Cannabis plants like a soil that drains well and has a pH of about 6.5. If the pH is too extreme then the plant will not be able to absorb nutrients properly. The pH can be raised by adding hydrated lime and can be lowered by adding sodium bicarbonate to the soil. The lime is slow acting so add it during the fall or at least one month before planting. Perlite, vermiculite, and sand can be added to soils that drain poorly. For indoor grows, using a sterilized soil is a must so as to avoid insect and other unwanted infestations.
Perlite(white) and vermiculite(tan) are soil conditioners. Perlite look similar to vermiculite but the later contains small amounts of nutrients. It's ok to use perlite on its own but vermiculite is best used in small amounts mixed with other mediums.
There are many kinds of soiless mix's containing a vast assortment of ingredients. Most contain things like Spaghnam moss, Perlite and Vermiculite.
Most soiless mixes retain water well and have great wicking action while still holding a good amount of air, making them a good growing medium for a variety of hydroponic and organic gardens.
My prefered soiless brand is called Pro-Mix and is readily available in hardware stores. It is comprised of a canadian sphagnum peat moss, perlite, vermiculite,and limestone mix (for ph adjustement)
Rockwool has long been among the most popular growing mediums available. Originally used as insulation it was called "Mineral Insulation" and was later developed for gardening in Denmark.
The shapes vary from 1"x1"x1" starter cubes up to 3"x12"x36" slabs, with many sizes in between. While versatility and ease have contributed to its popularity, there are several disadvantages to this type of growing medium which should be considered along with the pros before deciding on whether or not you want to use it.
This man-made product is often called grow rocks and is an extremely good growing medium. It is made by baking clay in a kiln. The inside of the clay pellets is full of tiny air pockets (much like lava rock) which makes this a light weight medium.
The pellets are great for ebb & flow systems or other systems that have frequent watering cycles (clay pellets do not retain much water so they need to be watered often so that the roots of your plants do not dry out). The rocks are often mixed with other growing medium(s) to increase oxygen retention.
Expanded clay pellets are rather expensive but they are one of the few kinds of growing medium that is easily reusable, which makes them a good choice for the long term. After you harvest your crop you can wash the clay rocks to remove all the old roots and then sterilize them with a 10% bleach and water mix (one part bleach to 9 parts water). The grow rocks can also be sterilized by using a mixture of Hydrogen Peroxide and water (use 1 or 2 teaspoons of 35% food grade hydrogen peroxide per gallon of water).
Coconut fiber is rapidly becoming one of the most popular growing mediums in the world. In fact it may soon be THE most popular. It is the first totally "organic" growing medium that offers top performance in hydroponic systems. Coconut fiber is essentially a waste product of the coconut industry, it is the powdered husks of the coconut itself.
There are many advantages - it maintains a larger oxygen capacity than rockwool, yet also has superior water holding ability than rockwool which is a real advantage for hydroponic systems that have intermittent watering cycles.
Coconut fiber is also high in root stimulating hormones and offers some protection against root diseases including fungus infestation. Dutch growers have found that a mixture of 50% coconut fiber and 50% expanded clay pellets is the perfect growing medium.
One word of caution about coconut fiber, you must be careful when you purchase coconut fiber. There is a commonly available, lower grade of coconut fiber that is high in sea-salt and is very fine grained. This lower grade coconut fiber will lead to disappointing results when used in a hydroponic system.
It can be used for hydroponics and soil grows (As soiless medium or as a soil ammendement)
A completely natural medium that is used as a major ingredient in most soiless mixes. Sphagnum moss can also be used by itself in a hydroponic system. Sphagnum moss makes a good fluffy growing medium that retains a high percentage of air and retains water well also.
The major problem with this growing medium is that it can decompose over time and you can get small particles that can plug up your pump and (or) drip emitters if you are using a recovery type hydroponic system.
This growing medium has been used for years and works well. Many or the earlier hydroponic systems that were commercially available to the public were gravel based ebb / flow type systems.
Pea gravel supplies plenty of air to the roots, but doesn't retain water, which means that the plants roots can dry out quickly if they are not watered enough. Another drawback to gravel is its weight, it's very heavy, and toting it around is difficult.
Pea gravel is usually fairly cheap and easy to find. You can easily reuse gravel as long as you wash and sterilize well between crops. After you harvest your crop you can wash the gravel to remove all the old roots and then sterilize them with a 10% bleach and water mix (one part bleach to 9 parts water). The gravel can also be sterilized by using a mixture of Hydrogen Peroxide and water (use 1 or 2 teaspoons of 35% food grade hydrogen peroxide per gallon of water).
Lava rock has been used successfully for years, it is light-weight and retains a fair amount of water in it's holes and pores. It is used most often in ebb & flow systems with frequent watering cycles.
With a good selection of first rate growing mediums available lava rock is used much less often these days. The drop in popularity is due mostly to the fact that the sharp edges of the rock can cause root damage to the plants, and in most areas of the world it can be hard to find lava rock that is not chemically treated.
Sand is the hydroponic medium that raises the most eyebrows. I don't like it personally because I feel that its small grains make it harder for the root system to develop. It does, however, hold moisture extremely well, and cleans easily ? you can reuse it to your heart's content, sifting it through a screen after each growing session. I would say the coarser the better when using sand, but that's just me.
Sand is wonderfully inert and is obviously pretty common. It has a tendency to hold salt more than does pea gravel, so be sure to flush it with pure pH balanced water on a regular basis.
When mixed with perlite, sand is a great medium to grow in, I'm told. Just watch that it doesn't foul any workings you might have in place to deliver your nutrient. Sand gets into everything, so if you're burning out water pumps like crazy, you now know why.
These lightweight pre-formed cubes are designed for propagation. A very popular medium for use when growing from seed or from cuttings. This product has a neutral pH and retains water very well.
The cubes are meant to be a starter medium and come in three sizes up to 2" x 2". They can be easily transplanted into practically any kind of hydroponic system or growing medium (or into soil).
Jiffy Peat Pellets
These peat pellets are designed for propagation. Also a popular medium for use when growing from seed or from cuttings.
Peat Pellets made of Canadian sphagnum peat moss permit abundant aeration, uniform drainage and easy root penetration. Peat Pellets are made with small amounts of lime (balances pH) and fertilizer (to help seedlings get started). These compact pellets swell up when water is applied to form round pre-dibbled growing pots. The peat is held together by a biodegradable mesh net and can be transplanted with the seedling when roots push through the netting. Transplant shock is greatly reduced because the entire pot can be planted without disturbing the roots.
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