Can You Go From Soil to Rockwool?


When it comes to planting, many gardeners love using either soil or Rockwool to grow plants. Rockwool is great for small plants or plants you intend to move from the Rockwool to either soil or a hydroponic garden. Could you move a plant from soil to Rockwool?

It is possible to move a plant from soil to Rockwool, though it often isn’t practical. Moving a plant from soil to Rockwool would likely mean moving ungerminated seeds to Rockwool, only to eventually move the plant from the Rockwool after three to four inches (7.62-10.16 cm) of growth.

Rockwool certainly has several benefits that make it great for growing new plants. Let’s take a deeper look at what Rockwool is, why it’s great for growing plants, how to move a plant from Rockwool to another substrate, and how you can use Rockwool to clone a plant.

Rockwool Explained

To grow plants in Rockwool, it is best first to understand what Rockwool is. Rockwool is a type of substrate, the surface or material a plant grows in, typically used to start seeds, clone plants, and grow plants in hydroponic operations. Rockwool is similar in texture and structure to materials like steel wool and is not naturally occurring.

Instead, Rockwool is an artificial material created by combining Basalt rock and chalk at incredibly high temperatures. When these substances are melted down and combined, they make a lava-like substance that, when cooled, results in a group of fine fibers layered upon one another. This layering creates a robust and breathable material suitable for growing plants.

Rockwool comes in several shapes depending on the level of the plant’s growth and size requirements for its roots. The various shapes are as follows:

  • Blocks suitable for growing multiple plants at once.
  • Cubes are ideal for growing one plant.
  • Starter plugs are best for seeds that have not yet sprouted.
  • Large slabs that are about half the thickness of the blocks.
  • Mats provide a very thin layer for plants starting to grow.

Rockwool, though compatible for plant growth, does miss a few qualities that make it less ideal for plant life. Rockwool, made from stone, has no nutritional benefits, meaning plants growing in Rockwool need supplemental nutrients. 

Rockwool’s acidity levels (pH) are suitable for plant life. Gardeners using Rockwood need to use special chemicals to adjust the acidity of the material depending on the plant.

Rockwool Advantages and Disadvantages

Though Rockwool has the limitations mentioned previously, it is also an ideal substance for growing small plants or starting plants from seeds. Rockwool is a natural medium of basalt and chalk, making them a popular choice in organic farming. 

Rockwool has numerous benefits, such as:

Rockwool Facilitates Quick Changes To Root Conditions 

Rockwool makes it easy for gardeners to quickly change the plants’ root conditions which is not always easy to achieve in soil mediums. For instance, if you over-fertilize your plant, you may easily leach out the excess nutrients through rinsing actions. Rockwool allows you to expedite changes in your plant root zone and better control your plant growth.

Breathable and Compact

Rockwool’s tiny fibers are breathable and, though compact, are somewhat flexible because a plant’s roots can move and grow around the fibers. This flexibility means that a new plant can develop a robust root system that will help supply it with water and nutrients as it grows. 

Soil mediums don’t always provide adequate breathability depending on your choice of soil medium. 

Rockwool Provides Enhanced Water Absorption

Additionally, Rockwool’s fibers help absorb the perfect amount of water and nutrients for a plant to survive. While excess water and nutrients will flow through the fibers and out of the surface, just enough water and nutrients will cling to the Rockwool fibers, allowing the plant access to the perfect amount of materials.

The Rockwool Material Is Sterile

Rockwool has another benefit in that it is a controlled substance, meaning that it has no negative factors that grow within it. There are no other seeds in Rockwool except for the ones you plant. 

This control makes conditions where there is no competition for your plant, and you do not need to deal with invasive plants like weeds trying to kill your sapling. Additionally, Rockwool does not have any diseases inside of it that some soils do, making it very safe for young plants.

Rockwool Disadvantages 

However, one important consideration when using Rockwool is that it can cause human health issues. The minute fibers can irritate your eyes, skin, and lungs, and you should consider a dust mask when using the Rockwool medium. When using Rockwool, also use gloves and wash your hands. Do not work with Rockwool that has dissolved into dust.

Moving Plants From Rockwool

Generally, people do not move plants from soil to Rockwool, but people very frequently move plants from Rockwool to soil or another substrate. However, because Rockwool is used most often for new plants, it is essential that when moving a plant from Rockwool, you are incredibly delicate as these plants are very fragile.

You should follow these steps while moving your plants: 

  1. Start by loosening the Rockwool around the roots of the plant. 
  2. Open the Rockwool at the top of the cube where the plant has sprouted.
  3. Follow the main roots through the Rockwool and untangle them from the Rockwool fibers. This action is acceptable if you need to trim some of the roots to preserve the plant.
  4. Once you have removed the plant from the Rockwool, spray it with a small amount of water to clean off any excess fibers. While they will not damage your plant as it is transferred to soil, if you move it to a hydroponic system, they can cause a buildup of particles that can cause some damage to your system. Lightly spraying the plant with water will get rid of excess particles.
  5. After spraying the plant, gently dig a hole in the soil and place the plant into the hole. Try to spread out the roots so they are not tangled together and can reach sections of the soil.
  6. Then, gently cover the roots and stem in the soil so that it is safely in the ground but is not so compact the plant can’t breathe.
  7. Add nutrients and water as needed, and your plant will grow.

If you add the plant to a hydroponic system, spread out the roots evenly and adjust the plant’s nutrients, acidity, and water levels to thrive.

Cloning Plants Using Rockwool

If you want to clone a particular plant for whatever reason, you can use Rockwool. In this system, rather than moving the whole plant from soil to Rockwool, you are only adding a small part of the plant to the Rockwool, so a new plant can grow and thrive.

The process goes as follows:

  1. First, cut a small stem (about three or four inches or 7.62-10.16 cm) from the main plant.
  2. Dip the cut bottom of the stem in a rooting hormone so that the old stem will grow roots and develop a new plant rather than just dying. 
  3. Carefully add the stem to the top of the Rockwool, ensuring that the bottom of the stem is not sticking out from the bottom.
  4. Immediately after the plant is in the Rockwool, add water and nutrients to the Rockwool so that the plant can grow. Since the old stem is incredibly fragile at this point, be sure to add enough nutrients and water frequently, so the plant gets as much as it needs. What it does not need will wash through the Rockwool, so while you don’t want to overwater the plant, being generous is better than being conservative.
  5. Add the Rockwool to a warm area with light so the plant can begin the photosynthesis process. Within a few days, you will notice roots growing through the Rockwool. If this occurs, the stem has successfully converted into a plant genetically identical to the old one.

Final Thoughts

Starting plants in Rockwool or using Rockwool to clone plants can be incredibly effective and rewarding if done correctly. While people generally do not move a plant from soil to Rockwool because it is not the most practical, people often new plants from Rockwool to soil or another material. Typically, a plant is only moved from soil to Rockwool during cloning.

While Rockwool can be great for plant health, you must protect yourself when using Rockwool. Take proper safety precautions like wearing gloves and washing your hands after use. Never ingest Rockwool.

Alexander Picot

Alexander Picot is the principal creator of TheGrowingLeaf.com, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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