As soon as it warms up in the spring, our plants enter a period of intensive growth. Depending on the speed of their growth, regular transplanting into a larger pot is also necessary. Those that grow fast may need to be repotted twice a year, while the rest are enough to be repotted once every two years.
How to recognize that a plant needs transplanting?
The first thing that tells us that the plant needs to be transplanted into a new, larger pot is the roots emerging through the drainage holes at the bottom of the pot.
You should also be alerted to the need for transplanting by the rapid drainage of water after watering.
If you smell mold and rotting of the substrate, it may not be necessary to transplant the plant into a larger pot, but it is definitely necessary to change the substrate.
The same should be done if the roots look sick.
What substrate to choose?
One of the main conditions for the successful cultivation of plants is their growth in quality substrates, which will satisfy the plants’ needs for nutrients, at least in the initial phase of growth.
Today, specialized agricultural material stores, as well as “neighborhood” stores, offer various types of substrate. In this variety, we often don’t even know which substrate to choose. Those who are attracted by the low price and buy substrates that, as it will turn out later, are not really the best choice, fare the worst.
Most substrates contain peat as a base, to which certain micro and macro nutrients, special additives for easier water intake and release, and certain additives to improve the structure have been added. Each of the substrates has a certain higher or lower pH value, which makes it suitable for growing certain species. 
Most of the substrate is composed of a mixture of white and black peat, to which all the necessary micro and macronutrients have been added so that the plants have sufficient amounts of nutrients, at least for initial growth. Depending on the cultivated species, it is possible to choose some of the specialized substrates, such as a substrate for pelargoniums and petunias. There are also substrates for growing plants that prefer acidic soils, such as rhododendrons, camellias, heather, etc. These substrates have a lower pH (around 4.5) and are suitable for growing the mentioned plants.
How to prepare the substrate at home?
Although it is always advisable to buy already prepared substrates, this can sometimes require considerable material resources, especially for those who have a large number of potted plants on their terrace.
When planting and transplanting plants, many people use garden soil, which is not recommended, since many pests and weed seeds are present in garden soil. In addition, it is usually heavy and not suitable for planting potted plants.
But by mixing garden soil with peat and sand, we can get a good substrate for planting, especially outdoor potted plants.
The substrate for planting is prepared from 7 parts of garden soil, 3 parts of peat and 2 parts of sand. Instead of sand, perlite can be added to the substrate, which is much lighter.
As the planted plants will remain in the jar at least until the next year and the new transplant, it is necessary to mix the substrate with nutrients that will satisfy the basic needs of the plant. For every 20 kg of substrate, 25 g of bone meal, 25 g of superphosphate and 10 g of potassium are added. It is recommended to add 10 g of lime.
Sterilization of the substrate at home
For this procedure, you will need a metal container, aluminum foil and a thermometer. Place a layer of about 10 centimeters of substrate in the container. Moisten it with a sprayer. Cover the dish with aluminum foil, making sure that it is well covered on all sides. Stick a thermometer in the middle that will withstand the high temperature. Place the dish in a heated oven. When the thermometer shows the temperature of the substrate between 82 and 93 degrees C, leave the substrate in the oven for another half hour. After that, remove the container and let it cool for 24 hours. After that you can use it.
Choosing a pot
When transplanting, many make the mistake of planting the plant in a much larger pot than the one in which they were planted until then.
Slow-growing plants, i.e. those that have reached full size, are planted in the same pot in which they were planted until then, with a mandatory change of substrate. With large plants, which are difficult to handle, we only change the substrate in the surface layer.
All other plants, i.e. those that have not yet reached their full size, are transplanted into a pot one number larger than the previous one. This would mean that it is transplanted into a pot that is two centimeters larger in diameter than the existing one.
If we transplant the plant into a pot that is too large, it will spend all its energy on root development, while the above-ground part, which is the most interesting to us, will lag behind in growth for some time.
Transplantation
During each transplant, the plant experiences a certain shock, during which part of the small roots die. In order to prevent significant damage, it is extremely important to transplant the plant immediately after extraction, so that the damage does not become more significant due to drying out of the roots.
When removing the plant from the jar, it is very important not to pull it. That is why it is necessary to water the plant well a few hours before transplanting, so that it can be easily removed from the pot. The pot is shaken slightly. Hold the pot firmly with one hand, and grasp the base of the plant with the other. Gently tapping the pot, take out the plant.
Sometimes it is not very easy to remove the plant from the jar, most often if it is made of clay. Then we have nothing left but to break the jar with a light blow with a hammer.
You will use its fragments as a drainage layer in the new container (picture 1).
After removing the plant, gently loosen the lump and remove the rotten and damaged roots (picture 2).
Before transplanting into a new pot, we put a drainage layer 3-10 centimeters thick on its bottom, depending on the size of the pot. On top of this layer comes a layer of substrate on which the plant is placed. At the same time, care should be taken that the plant should be planted at the same depth at which it was planted before.
After that, fill the pot with the substrate, pressing it well with your hands. We make sure that there is about 3 centimeters of free space from the level of the substrate to the edge of the pot, so that during watering the water does not overflow over the edge of the pot.
The transplanted plant will find enough nutrients in the new substrate for the first two months of growth. After that, the plant needs to be fed with nutrients provided for it.
