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Once you start gardening, you do not know much – amateur gardeners just follow some of the most popular rules. Every beginner gardener puts rocks in the bottom of containers, without really understanding the purpose of the rocks and whether the plant needs them there or not.
In this article, you will learn more about the role of rocks in the plant pots – why are they put there, and most importantly, whether should you use them.
In this way, you will avoid some of the common beginner’s mistakes.
Does My Plant Need Rocks?
Well, it probably doesn’t.
Gardeners put rocks, or pebbles (sometimes even pieces of terracotta pots) because they believe that these will help with drainage and boost the circulation of air.
However, that doesn’t happen.
Drainage, Capillary Action and How They Are Affected by Rocks
Drainage is quite important since the roots of many indoor or outdoor plants do not tolerate soggy soil.
If it retains too much water, the roots will start to rot. Drainage holes on the bottom of the pots will pull any excess water that the plant doesn’t need, simply by gravity.
Of course, some amount of water has to be retained – it is held in the soil by substances that work like small sponges, and with capillary action, that retained water is delivered to the plant.
The gravitational force that helps the drainage and capillary action that delivers the water are two opposing forces.
Simply by choosing the proper potting mix, that has a fair amount of drainage material and using pots with holes, you can achieve good water drainage, and still, make sure that your plant has retained the amount of water it needs.
As you can see, the rocks do not play any significant role in this process. On the contrary, they can create major problems.
If you place a layer of rocks, the excess water isn’t able to leave the pot so quickly, and the roots are sitting in the water longer – later, this can cause the rotting of the roots and other diseases.
Also, rocks on the pot’s bottom will take up space – there won’t be so much space for the growing mix that roots are developing in. Thus, the growth of a plant could be slower and never reach its maximum.
What About Air Circulation?
As said, many gardeners place rocks since they believe that it will boost the circulation of air.
However, in these bottom layers of pots, space is entirely occupied by water – there are no air pockets that can travel from the bottom layers to the top ones, thus improving air circulation.
So, one myth is debunked!
If you want to boost the air circulation in the potting mix, create a few holes with a stick on the top layer of the soil. By doing this every few days, you will better the circulation of air.
Furthermore, if you cannot create these holes due to compact soil, then repot the plant.
When Are the Rocks Needed?
In certain situations, rocks are welcome and needed – but not for boosting either drainage or air circulation.
This is when you should use rocks:
1. The plant is potted in a big pot
In this situation, it is okay to place a layer of rocks.
Growing mixes can be quite expensive – well, expensive compared to rocks.
If the pot is big and you need a good amount of growing mix, you could mix the soil with rocks, so you use a bit less of the growing mix.
Do not go overboard with the rocks – they shouldn’t affect the drainage of the soil.
2. You are using a pot without holes
Well, in this case, you have two options – either get a new pot that has drainage holes or use gravel.
The good potting mix will release a certain amount of water, and if that water can’t leave the pot through the drainage holes, the roots will suffer.
If you add a layer of gravel, it will absorb the released water, but this isn’t a good long-term solution.
Will the Soil Wash Away Without the Rocks?
Soil can escape through drainage holes, and if it does happen, then you can add a rock to the bottom.
One rock is fine – it will cover the drainage holes and still allow water to flow over it, and reach the holes.
However, do not put many rocks.
Even better than rocks are thin, porous materials, such as filter papers or cloths. These will make sure that the potting mix stays inside the pot, and let water pass through them.
So, even if the soil is washing away, you still do not need rocks – there are other solutions.
Should I Repot My Plants?
After reading this, you are probably wondering whether you should repot the plants in whose pots you’ve placed rocks.
No need to worry!
Firstly, if you are using big pots, repotting isn’t necessary. Especially if the big pot is used for growing a smaller plant.
Remember one of those two situations in which the rocks are welcomed in a pot?
Well, this is one of those situations. Just make sure that you aren’t overwatering the plant, and everything will be fine.
On the other hand, if the plant is growing in a container that is proportional to its size, you should repot the plant.
Roots need space to grow – if they overgrow the pot, they will tangle around the rocks, and later repotting will be quite messy and exhausting.
Many plants also have delicate roots. So while trying to separate the roots from the rocks, you can accidentally damage its root system.
So, before you grab another pot and buy a new bag of potting mix, make sure that the plant can stand the repotting process.
You should repot only if not doing it is more harmful to the plant.
But remember, the best time for repotting is always spring and summer. If you repot your plant during winter, the chances are big your plant will die.