A Guide To Soilless Growing Mediums

The Vault Cannabis Seed Store Soilless Mediums

Growing cannabis in soil can be an excellent choice for certain types of growers. For those who like to do things traditionally or want to grow organic cannabis, soil is the best option. However, for many other growers, the soilless growing mediums are an attractive, mess-free alternative that can make growing a little easier. There are several benefits to using soilless growing mediums. They can provide better air circulation to roots, plants can be transferred with minimum fuss, and they store moisture and nutrients well. However, there are several different types of soilless mediums available. So let’s have a look at all of our options and their pros and cons.

Coco Coir

This medium is made from coconut husks and is probably one of the most popular soilless growing medium. It works well on its own or can be mixed with another medium to improve airflow to the roots. The fibres of the coconut are excellent for collecting and storing water and nutrients. Despite being able to store moisture they are resistant to harmful bacteria and mould. This medium is also eco-friendly and renewable and is stuffed with nutrients. The PH balance is also ideal for cannabis plants, this is an excellent option for those who are starting to play with soilless growing.


Rockwool is also extremely popular and is the most widely used medium. It holds water well and allows plenty of air to get to the roots. Rockwool is porous, inert, sterile and non-degradable. It gives plenty of support to the roots during growing and allows them to take in all of the oxygen they need. Rockwool often comes in cubes and is ideal for supporting seedlings as they get big and strong.


This is a soft and spongy medium that mixes well with others to create an excellent growing environment. It is best known for its ability to hold water and is excellent for helping clones grow strong roots. It is also a great nutrient provider and has traces of aluminium, silicon, phosphorus and magnesium. All of these are necessary for a healthy plant and will increase the growing vigour of new babies. We need to make sure we get the vermiculite specifically for plant growing to ensure no nasty extra chemicals.

Peat Moss

This used to be the most widely used and popular medium before Coco Coir and Rockwool came along. It also retains a lot of moisture so is usually used in hydroponic setups where the roots are drawing a nutrient solution straight from the reservoir. Peat Moss is extremely high in fibre and has an ideal PH level for cannabis growing.


This is perfect for anyone worried about root rot as it drains quickly and stops the roots from being submerged in moisture for too long. However, it can’t buffer on its own and will usually need to be mixed with another growing medium. It can also be used in soil to provide better aeration to the roots.

Expanded Clay

This is one of the great reusable varieties of growing medium. Some once used can be cleaned and used again, saving a bit of money and being eco-friendly. Essentially expanded clay is just that, small clay pellets cooked in a kiln until they expand. Each of these pellets has a little pocket inside that will store the water and nutrients for the plant. They will also store air, adding a little extra aeration to the roots. These are popular because even though they hold the nutrients, water and air they also drain well. Once again these are very popular in hydroponic systems.


If we are choosing between growing mediums sand probably isn’t in my top 10. This is primarily because it is still messy and dense without giving anything extra. The only real use for sand as a medium is to mix it with another medium that requires a little more structure.


Gravel is common in hydroponic setups to provide root structure and support. It may be a little heavier than some options, but it is inert and it drains well. It is also much cheaper than a lot of other soilless mediums and provides plenty of air to the roots. Gravel needs to be soaked and have its PH adjusted before using. Growers using gravel don’t need to worry about overwatering because excess water won’t hang around in amongst the stones. Of course, these are also reusable as long as they are properly cleaned.

Pumice Stone

Pumice is famous for its porous structure and its lightweight build. It is a natural volcanic rock that has a thousand uses. Its surface is sponge-like which allows it to store water, air and nutrients. It is extremely easy to work with, making it a good choice for those who are new to growing. Pumice Stone is sometimes called Lava Rock when being used for cannabis growing. The only potential downside to pumice is that it can be sharp in places and has the potential to cut the roots. However, it is soft so as long as we check for sharp bits before planting they are extremely easy to sand down. Pumice Stone is probably one of the best overall options available as it is also inexpensive.


Foam can work well to help with root structure but runs a risk of over absorbing water. It is long-lasting and extremely easy to clean, making it reusable, but it can be tricky to drain risking root rot.

These are all of the primary soilless growing mediums and as we can see each of them has its ups and its downs. We need to consider the growing space, strain, style of growing and environment to decide which one would be best suited. When in doubt it’s usually best to go for something like pumice, Rockwool or Coco Coir that are suited to many environments. As always do plenty of research before making any decisions.

Remember: It is illegal to germinate cannabis seeds in many countries including the UK. It is our duty to inform you of this fact and to urge you to obey all of your local laws to the letter. The Vault only ever sells or sends out seeds for souvenir, collection or novelty purposes.

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