How To Start Seeds In Rockwool. Best 3-Step Guide

If you want to learn how to start seeds in Rockwool, you have three steps to understand. Rockwool is a popular growing medium, especially for hydroponics. Therefore, it’s not surprising that one wants to know how to use it to their advantage in germinating seeds. 

In addition to starting seeds in the greenhouse to encourage germination, using Rockwool as the medium for them can be useful because of its excellent moisture retention. Remember that one of the factors that one must nail to ensure sprouting is providing moisture without overwatering that can dampen and kill the seeds. Rockwool will not create a waterlogged environment for the seeds, but it won’t dry them as well. 


How To Start Seeds In Rockwool. Best 3-Step Guide

How To Start Seeds In Rockwool Successfully


Step #1. Preparation

Being a soil-less growing media, you can expect to prepare the Rockwool cubes first before sowing the seeds in them. For example, it’s worth noting that this media has a pH of around 7 to 8, which is high for seeds. You can adjust the cubes’ pH levels by soaking them in water, and this should result in a level between 5.5 to 6.5, which is more appropriate for seed germination. 

Use slightly acidic water to do so, or make one using water and lemon juice. A solution around 5.5 to 6.5 pH would be ideal, and you can use a pH test strip to achieve this. Once you have the slightly acidic water, soak the cubes in it for at least an hour. 


Step #2. Planting

After an hour, you can use the cubes and plant the seeds at their top and pinch the hole close. You should find the hole and place two seeds inside or use an object to comfortably press the seeds down to the bottom of this hole. After planting, add more moisture using a hydroponic nutrient solution to encourage germination and transplant once you have 3-inch tall seedlings. 


Step #3. Maintenance

As mentioned earlier, the main advantage of starting seeds in Rockwool is that it provides moisture at the ideal rate. Without the danger of drying or overwatering, the water should promote germination by activating the seed’s enzymatic reaction. However, you still need to do the necessary maintenance practices to ensure success. 


Encourage germination

For example, the greenhouse is a suitable environment for hydroponic systems because you can control the internal conditions. This is especially useful for starting plants that are more challenging because they haven’t established themselves yet. Those who start seeds in Rockwall cubes can place them somewhere between 70 to 80°F and inside a humidity dome to create an ideal sprouting environment. 


Encourage seedling development

The maintenance practices at this point involve misting when the cubes start to dry out. Be mindful not to overwater the cubes or accidentally allowing it to dry out. Once you notice sprouting, depending on the plants you’re growing, remove the dome and place the cubes under grow lights to support development further. 

Much like in starting seeds in pots, you want to thin the plants so that only the healthiest remains per cube. This could also be the taller plant, and you can cut off the shorter one. You don’t need to pull out the undesirable plant because you run the risk of dislodging the preferred one at the cube. 


How To Transplant From Hydroponics To Soil

Starting seeds in a soil-less medium and transplanting the plant to soil is common among growers. However, you have to be mindful of this practice to avoid transplant shock and other potential problems. For example, where should you plant the transplants?


Transplant preparation before soil planting

You can use a large pot to anticipate the root system of the transplants. Allocate a space of around 4 inches to ensure that they have room for their roots. Fill this with a growing medium like a soil-less peat mixture.

This will act as an environment for the plants before being directly in the soil. After planting, you must add a nutrient solution to help the plants adjust. It’s also vital to water them immediately to reduce the risk of shock. 

Wait for a week to cut back on watering and check your calendar if you can transplant outdoors. 


Hardening and transplant shock

More so, don’t forget the importance of hardening the plants gently before permanently planting them outside. If you notice withering of leaves and stems, this can be a sign of transplant shock. You can water the plants to help them and trim it to at least one third to strengthen their roots. 



With extensive knowledge of various mediums, one shouldn’t feel intimidated by growing plants from seeds. If you know how to start seeds in Rockwool and have a greenhouse, you don’t risk encountering common germination drawbacks from low moisture availability and unstable environments. The key is preparing the cubes first by adjusting their pH level and placing them in the greenhouse to encourage sprouting further. 

Much like growing seeds in other mediums, you must maintain soil moisture by misting and using a humidity dome. You can also adjust the temperature in the greenhouse and wait for seedlings to develop. At this point, wait for the plants to reach an ideal height for transplanting, and you should have vigorous plants from Rockwool. 


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How To Prevent Root Rot In Hydroponics: 3 Useful Tips

If you’re a newbie gardener who’s looking to find ways to hone your skills, you’d want to learn how to prevent root rot in hydroponics even before this problem affects your plants.

Hydroponics can be advantageous to crops in more ways than one. However, it also comes with risks of diseases, such as root rot, which can be destructive or even lethal to your plants.

Unfortunately, there are no effective methods to recover the wilted parts that were affected by the root rot once it hits your plants. The only thing you can do if you do not want this catastrophe to befall your crops is to prevent it before it happens. Read on to learn more about this subject.


What is Root Rot?

Root rot is a disease that attacks the plant roots and causes them to suffer decay. This usually happens when a lack of oxygen supply occurs in the substrate.

To give you an idea, think about plant roots that are submerged in water that only has a little oxygen in it. Over time, the plant suffocates and dies.

Aside from rot and decay, this disease also leads to the proliferation of fungi that are naturally present in the soil. These include Rhizoctonia, Alternaria, Pythium, Botrytis, Fusarium, or Phytophthora. As soon as fungi colonies start to grow, they tend to target the weakened roots and infect your precious plant babies.

Once the plant becomes infected, they won’t be able to take in what they need to grow – water, oxygen, and other nutrients. When this happens, it won’t be long before the plant dies.


What is Hydroponics?

In case you’re not aware, the term hydroponic is derived from a Latin word that means “working water”. To put it simply, hydroponics is an art that involves growing various types of plants without soil. If you’re like most people, the first thing that comes to mind when somebody talks about hydroponics would be a picture of plants with roots suspended into the water without using any type of growing medium.


Avoiding Root Rot in Hydroponic Systems

Detecting and identifying root rot can be tricky. When your plants get infected, their leaves and roots gradually wither until the whole crop itself dies from the lack of nutrients, which is a common symptom of many diseases.


What causes root rot in hydroponics?

One of the requirements in hydroponics systems is oxygen. Without it, your plants are basically on the road to death. On the other hand, lack of such is one of the major triggers for root rot, and it must be avoided at all costs.

Just like when planting in soil, you loosen up the ground so that your plants’ roots can have their required intake of oxygen. That is the case for crops grown in aqueous solutions as well. If they cannot breathe, they would not be able to grow.

Another agent for root rot is the temperature. The last thing you would want in your system are parasites that leech nutrients intended for your plants and infect the water during the process. In common terms, these fungi are called molds.

One of the best breeding grounds for these is warm and moist areas. For this reason, if the water temperature inside your reservoir is high, then you are susceptible to it. Something as minor as letting the solutions exposed to sunlight can already be a risk factor.


3 Useful Tips on How to prevent root rot in hydroponics

There is good news! Root rot in hydroponics can be prevented! Just follow these tips:

Tip#1: Use the right air pump

If you do not want root rot to affect your plants, you merely have to avoid its causes. If you need oxygen, keep the water bubbling by providing an air pump of appropriate size, and also give importance to proper ventilation in the room.


Tip #2: Maintain the temperature

The temperature should be maintained within the 70 to 80 degrees F range. Get rid of any materials that can make your system vulnerable to infections, and make sure not to disturb your crops while they are trying to grow.


Tip #3: Get rid of the rotten parts

However, if you failed in preventing the disease, then the rotten parts should be removed immediately. Cut them off as there is no chance of reviving them, and focus on the potential new growth instead. Fix your hydroponics system and eliminate the risks.


Why Give Greenhouse Gardening a Try?

Greenhouse gardening offers numerous benefits to greens aficionados who dare to take their gardening experience to the next level. Aside from acting as a shield against the effects of inclement weather, a mini, hobby, or semi-pro greenhouse can also serve as a protective layer that keeps harmful bugs and critters at bay.

What’s more, its enclosed structure allows you to control your plants’ growing conditions including the temperature, light, moisture, and ventilation of the greenhouse’s internal environment. With a controlled environment, you’ll be able to extend growing seasons and grow plants that aren’t native to your area.



No matter how well-informed you are about how to prevent root rot in hydroponics, you cannot completely eradicate the risks. Therefore, to avoid the worst-case scenario, you should be prepared to sacrifice the infected for the sake of others. While you’re at it, consider trying your hand at greenhouse gardening as well.


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