If you’re looking for a soilless
substrate for seed starting, stem rooting or hydroponics,
consider using rockwool growing medium. This wool-like material is made by
melting basaltic rock and spinning it into fine fibers. Rockwool for plants is
then formed into easy-to-use cubes and blocks. But is rockwool safe to use for
the production of food?
Advantages and Disadvantages of Growing in Rockwool
Safety: Formed from natural materials, rockwool
contains no harmful chemicals. It’s safe to use as a rooting medium and
substrate material for plants. On the other hand, human exposure to rockwool
represents a health issue. Due to its physical properties, rockwool growing
medium can cause irritation to skin, eyes and lungs.
Sterile: Since rockwool for plants is a manufactured
product, it’s contains no weed seeds, disease pathogens or pests. This also
means it contains no nutrients, organic compounds or microbes. Plants growing
in rockwool require a balanced and complete hydroponic solution to meet their
nutritional needs.
Water Retention: Due its physical structure, rockwool
drains excess water quickly. Yet, it retains small amounts of water near the bottom
of the cube. This unique property allows plants to attain adequate hydration
while allowing more air to circulate and oxygenate the roots. This difference
in moisture levels from the top to the bottom of the cube makes rockwool ideal
for hydroponics, but it can also make it difficult to determine when to
irrigate the plants. This can result in over-watering.
Reusable: As a rock derivative, rockwool doesn’t
break down or erode over time, thus, it can be reused many times. Boiling or
steaming between uses is recommended to kill pathogens. Being non-biodegradable
also means it will last forever in a landfill, making rockwool for plants a
not-so environmentally friendly product.
How to Plant in Rockwool
Follow these easy instructions when using rockwool growing
medium cubes or blocks:
- Preparation: Rockwool has a naturally high pH of 7 to 8. Prepare a solution of slightly acidic water (pH 5.5 to 6.5) by adding several drops of lemon juice using pH test strips to attain the correct acidity. Soak the rockwool cubes in this solution for about an hour.
- Sowing Seed: Place two or three seeds in the hole at the top of the rockwool growing medium. Water using a hydroponic nutrient solution. When the plants are 2 to 3 inches (5 to 7.6 cm.) tall, they can be transplanted into soil or placed in a hydroponic garden.
- Stem Cuttings: The night before taking the stem cutting, water the mother plant thoroughly. In the morning, remove a 4 inch (10 cm.) cutting from the mother plant. Dip the cut end of the stem in honey or rooting hormone. Place the cutting in the rockwool. Water using hydroponic nutrient solution.
Rockwool is the substrate of choice for many large
hydroponic farms. But this clean, pathogen-free product is also readily
available in smaller-sized packages specifically marketed for home gardeners.
Whether you’re dabbling with cultivating lettuce
in a hydroponic jar or you’re setting up a larger system, growing in
rockwool gives your plants the advantage of superior root zone technology.
If you’re looking for a soilless
substrate for seed starting, stem rooting or hydroponics,
consider using rockwool growing medium. This wool-like material is made by
melting basaltic rock and spinning it into fine fibers. Rockwool for plants is
then formed into easy-to-use cubes and blocks. But is rockwool safe to use for
the production of food?
Advantages and Disadvantages of Growing in Rockwool
Safety: Formed from natural materials, rockwool
contains no harmful chemicals. It’s safe to use as a rooting medium and
substrate material for plants. On the other hand, human exposure to rockwool
represents a health issue. Due to its physical properties, rockwool growing
medium can cause irritation to skin, eyes and lungs.
Sterile: Since rockwool for plants is a manufactured
product, it’s contains no weed seeds, disease pathogens or pests. This also
means it contains no nutrients, organic compounds or microbes. Plants growing
in rockwool require a balanced and complete hydroponic solution to meet their
nutritional needs.
Water Retention: Due its physical structure, rockwool
drains excess water quickly. Yet, it retains small amounts of water near the bottom
of the cube. This unique property allows plants to attain adequate hydration
while allowing more air to circulate and oxygenate the roots. This difference
in moisture levels from the top to the bottom of the cube makes rockwool ideal
for hydroponics, but it can also make it difficult to determine when to
irrigate the plants. This can result in over-watering.
Reusable: As a rock derivative, rockwool doesn’t
break down or erode over time, thus, it can be reused many times. Boiling or
steaming between uses is recommended to kill pathogens. Being non-biodegradable
also means it will last forever in a landfill, making rockwool for plants a
not-so environmentally friendly product.
How to Plant in Rockwool
Follow these easy instructions when using rockwool growing
medium cubes or blocks:
- Preparation: Rockwool has a naturally high pH of 7 to 8. Prepare a solution of slightly acidic water (pH 5.5 to 6.5) by adding several drops of lemon juice using pH test strips to attain the correct acidity. Soak the rockwool cubes in this solution for about an hour.
- Sowing Seed: Place two or three seeds in the hole at the top of the rockwool growing medium. Water using a hydroponic nutrient solution. When the plants are 2 to 3 inches (5 to 7.6 cm.) tall, they can be transplanted into soil or placed in a hydroponic garden.
- Stem Cuttings: The night before taking the stem cutting, water the mother plant thoroughly. In the morning, remove a 4 inch (10 cm.) cutting from the mother plant. Dip the cut end of the stem in honey or rooting hormone. Place the cutting in the rockwool. Water using hydroponic nutrient solution.
Rockwool is the substrate of choice for many large
hydroponic farms. But this clean, pathogen-free product is also readily
available in smaller-sized packages specifically marketed for home gardeners.
Whether you’re dabbling with cultivating lettuce
in a hydroponic jar or you’re setting up a larger system, growing in
rockwool gives your plants the advantage of superior root zone technology.