Rockwool Growing Cannabis Seed Strains

Cultivating Top Shelf Buds in Rockwool Explained

Rockwool growing cannabis seed strains is easy, clean and productive. Professional growers of flowers, veggies and all types of plants like rockwool because it is very clean, light weight, sterile and allows for the management of air to water ratios at the roots to maximize results.  Rockwool is also great because you only need a very small amount to grow a lot of bud versus soil.  It’s not hard to yield a half pound plant in only a six inch pot or cube of rockwool.  When the crop is done there is only a small and light weight amount of media that has to be disposed of or repurposed–way easier than lugging giant bags or bales of moist dirt around.

What is Rockwool?

Rockwool is a fibrous. porous and inert material usually made from spinning molten basalt rock like cotton candy and letting it cool.  It is then cut into cubes, slabs or granules and wrapped in plastic sleeves. Rockwool is relatively inexpensive and fairly widely available.There is also a material used for growing crops called “glass wool”.  It is less common but it shares similar properties to rockwool.  Note to only to use horticultural grade rockwool–industrial grades may be used as fire retardant insulation. They are not the same, although they may look similar!

Why Rockwool for Growing Cannabis?

There are several good reasons why rockwool is popular with professional growers—home growers may also share and reap similar benefits, including:

Rockwool growing cannabis seed strains can yield heavy crops without a whole lot of growing medium.  Because hydroponic growing nutrients supply all of the necessary elements hungry buds need to swell to maximum potential, the growing medium volume doesn’t need to be nearly as big as with soil.

Rockwool growing cannabis seed strains gives growers lots of control over the root environment, making it easier to keep roots happy and more productive with more air around the roots.  Rockwool is very porous and water moves very well through it–roots don’t need to be kept soaking wet; it makes them grow healthier and take in more nutrients. Using flood and drain or drip trays with a reservoir, pump and a timer gives easy control over air to water ratios 24/7.

rockwool cannabis growing

Since automation is easy with rockwool gardens, growers can spend more time tending the crop doing important things like pruning, checking for issues and managing the growing environment–all the many little jobs that add up to healthier crops of buds that yield heavier!

Rockwool growing cannabis seed strains is very neat and tidy.  Horticultural grade rockwool is totally sterile–guaranteed not bring any problems into the garden like root disease causing organisms or insect eggs and nematodes.  The same cannot be said of most garden soils.

How To, Rockwool Growing Cannabis Seed Strains Basics

For cannabis seedlings, use starter plugs or two inch rockwool cubes.

For young vegetative cannabis seedlings, ie two to four weeks, use three to four inch rockwool cubes or loose rockwool flock in pots.

For final transplant before flowering and budding, use six inch rockwool cubes or one gallon pots with rockwool flock or three to four inch cubes on top of rockwool slabs.

Pre-treat rockwool before growing your cannabis seed strains.  This is to help condition it for proper pH levels before use because rockwool is very alkaline (high pH). It’s easy to do–just soak for 24 hours or as directed by label in a mild fertilizer solution with a pH of 5.5. Liquid pH test kits or test strips are inexpensive, easy to get and accurate enough.  Digital testers are also available.

Once planted, DO NOT OVER WATER ROCKWOOL! Rockwool is very porous, you want more air around roots—keeping it soaking wet does not help, it hurts.  Let rockwool dry out to half of the wet weight (get a feel for it, pick it up) before lightly irrigating again. Rockwool is somewhat forgiving, thankfully.  However, a long stretch of staying fully saturated can create problems in some root sensitive strains.

For feeding crops of buds growing in rockwool only use mineral hydroponic nutrtients.  Organics will clog up the pore spaces and create all kinds of problems.  Following a hydroponic feed chart using hydroponic fertilizers in each growth phase makes it easy for anyone to get heavy yielding and high quality crops without a lot of hassles or mess.  Just stick to the formula and keep a healthy environment and reap the rewards!

If you want to learn rockwool growing cannabis seed strains step-by-step with lots of details on everything you could possibly need to know, check out our upcoming book “Growing Top Shelf Buds”.  This guide has lots of photos and expert advice; a MBA Monster Breeders, Reeferman Genetics and OldSchoolBA collaboration.  There’s a lot of knowledge packed in those pages.  To get yours, email info@oldschoolba.com and mention “Top Shelf Book”.