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planting seedlings in rockwool

How to Grow Lettuce from Seed in Rockwool

In this tutorial we are going to learn how to grow lettuce (type: May Queen) from seed in the rockwool as growing medium. The process is easy and straight forward.

Equipment need

Before we start we have to make sure that we are having all necessary parts for growing lettuce. The parts that we need are:
– A pack of May Queen Lettuce seeds
– A sheet of rockwool blocks
– A water pH Meter
– A pH Minus solution
– A thermometer that can measure the temperature of the water and the temperature of the air
– A enough large transparent food container with cover

All the things needed in this tutorial you can buy at local garden or hydroponics store. Or if there is none of them around, you can find them on this Amazon list here: http://amzn.to/1TkwktC

Prepare rockwool for planting lettuce

  1. First we take a bowl and that is large enough to have all of our rockwool soaked in water.
  2. Fill 3/4 of bowl with tap water
  3. Take a pH meter and remove the black cap from it.
  4. Place pH meter tip (the point that cap was placed before we removed it) in water and turn the pH meter ON.
  5. Wait few minutes for value to stabilize
  6. If the pH level is higher than 4.0 then add few drops of the pH Down (or pH Minus) liquid to bowl and stir it well and go to 3. point of this step and repeat points 3,4,5 and 6 until you get pH level of the water in bowl to be 4.0
  7. Now you can put cap back to pH meter and turn pH meter off and place it somewhere else
  8. Take the thermometer and check the temperature of the water
  9. If temperature is not in range of 15 to 20 ВєC (59 – 68 ВєF) then heat up or cool down water so it’s temperature is in our desired temperature range
  10. Now we can place our rockwool in the bowl with water
  11. Put it aside for 30 min and then place it on the steep surface so the rockwool can release all unnecessary water.
  12. Leave the rockwool on that surface for 15 min before proceeding to next step.

Make holes in the rockwool

In case that your rockwool is combined with many pieces in one big piece now is the time to split it in those smaller blocks.
1. Take a small stick, wooden or plastic it doesn’t matter, just make sure that it is not more than 2.5mm wide. For example you can use stick for placing small meat pieces on the grill or toothpick.
2. From bottom of the stick measure 6 mm and with the marker or pen write a tin line exactly on 6mm point from the bottom of the stick
3. Take each block of the rockwool and push the stick in it so that you reach that 6mm mark that you’ve previously made. Please take special caution to make sure you don’t push the stick more than 6mm in the rockwool.

Place the seeds in rockwool holes

  1. Takeout the seeds from packaging
  2. Place a single seed in each hole that we’ve previously made in the rockwool.

To make it easier, you can use the stick that we used before and carefuly with the stick push the seed inside the hole. Also make sure that you don’t push the seeds more than 6mm in the rockwool.

You can also put a ice cream stick on the edge of the rockwool and write the date so later when you plant more lettuce you can easily see when are the seeds planted

Place the seeds container near the window

  1. In the transparent food container place all the rockwool blocks so the holes are facing up and close the lid
  2. With thermometer check the temperature in the room, it should be in range of 15 to 20 ВєC (59 – 68 ВєF). In case your room temperature is warmer or colder than accordingly adjust the temperature so it is in between 15 and 20 ВєC (59 – 68 ВєF)
  3. Place the food container near the sunny window

In next 2-4 days we should see small sprouts coming out. During this time please maintain the room temperature in between 15 and 20 ВєC (59 – 68 ВєF), also check the rockwool and see if it’s drying out, and if necessary spray water on it so it get moisture but make sure to not over water the rockwool so when you pull the block of the rockwool up, water should not leak from it.

How to Grow Lettuce from Seed in Rockwool – In this tutorial we are going to learn how to grow lettuce (type: May Queen) from seed in the rockwool as growing medium. T…

Growing In Rockwool Cubes – Is Rockwool Safe For Plants

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. A wool-like material, rockwool for plants is easy to use and available in cubes and blocks. Learn about rockwool in this article.