When to repot plants?
Basically, spring is perfect for “repotting” your plants. At the beginning of the growing season in mid / late March is the best time for most plants to be planted, transplanted and also repotted.
You have to keep in mind that for plants in pots the growing season often starts earlier than for plants outdoors, because the soil in the pot warms up faster than the soil. Thus, in average spring weather here also usually need to start watering and fertilizing earlier. As soon as the first shoots, leaves or spears grow (depending on the plant genus), the plant is in full bloom again and is strong enough for repotting.
For houseplants, spring is not quite as crucial, as it is usually warm in the room all year round, but due to the increased amount of light in spring and summer, repotting at these times of year is also recommended. Theoretically, of course, it is possible to repot at other times of the year if necessary, but it should be remembered that plants that are in a resting phase in autumn and winter, for example, should not be subjected to “repotting shock”.
At some point, our houseplants reach the point where they need a new pot. But how can you tell if the plant needs repotting? What is the best time for this? Does it always have to be special soil? This and more tips you will learn here.
Why repot plants?
Newly purchased plants of any kind, you should repot as soon as possible and immediately, regardless of the season. But why is this recommended?
In most cases, the old “culture pot” is too small for the plant that grew in it. Garden centers and growers want to save space and money and often leave plants in small pots for far too long. Also, in many cases, the roots are already growing out of the drainage holes or the pot is even already damaged. In addition, it is difficult for the layman to recognize how old the soil in the pot already is and whether the lime, salt and fertilizer concentration is still beneficial to the plant. To whom has it not happened that the condition of a newly purchased plant has noticeably deteriorated after a short time!? This is usually not due to the lack of green thumb, but the small pot with old and used soil.
The only exceptions to repotting immediately are flowering plants such as flowers, bulbs or orchids. Here you can also wait a little with the repotting, because there is a risk that the flowering plant loses its flowers because of stress during repotting.
Nevertheless, repotting should definitely be done when it is obvious that something is wrong:
Pot is damaged
The substrate has a strong smell
The roots grow out of the holes or are brown
In general, plants that are kept permanently in pots should be repotted every 2 years. As a rule, after 2 years the pot is fully rooted and the substrate is largely “used up”, so that the plant needs more space and new soil. If you skip repotting, brown leaves or, depending on the plant genus, other deficiency symptoms may appear. Unlike outdoors, there is virtually no soil life in the planter. Therefore, fertilizer and fresh soil must be added regularly. If you originally chose a very large pot compared to the size of the plant and the plant is healthy, the repotting cycle can be extended to 3 years.
What do you need to repot?
The right pot size
First, you should look at what size the culture pot and the purchased plant and think about what pot size should be the next. There is no rule to which you must necessarily adhere here. Usually it is beneficial to the appearance and health of the plant to transfer the upper volume of the greenery and possibly stem also to the root area and thus to the pot size.
Example: If the plant has a height and, if necessary, width of about 20 cm, you can use a pot with a diameter of 23 cm, for example. To facilitate later repotting, we always recommend using the plant inserts that we offer for most planters. Especially indoors, this is mandatory. Alternatively, of course, you can simply replant larger culture pots. If the plant is already larger, choose the next larger container.
The right substrate
For almost all plants, coco soil is the ideal substrate. It is structurally stable, absorbs water and is still very airy and permeable. It is much gentler on roots and more environmentally friendly than peaty soil. Once you swell it with about 4 to 5 liters of water, you will get almost 10 liters of loose substrate from a 650 g brick within a few minutes.
You can also mix the Queller soil with other substrates. Mix garden soil or clay into the Queller soil to make the substrate a little firmer. Alternatively, mix in expanded clay or other mineral substrate to make the soil even looser and more water-permeable. Many plant species have their own preferences.
Keep in mind that the Queller soil is not pre-fertilized and completely nutrient-free. Here it is advisable to use slow-release fertilizer already during the swelling process of the soil and mix it under the soil. However, pay attention to the dosage indicated on the packaging.
There are also plants which should not be placed in coco soil. These include orchids and cacti, which should be planted directly in mineral substrate due to the necessary higher water permeability. Or hydrangeas and rhododendrons, which prefer more acidic substrate.
The right drainage
Whether with or without drainage holes and whether indoors or outdoors, drainage is always useful.
Outdoors, protect your plants and containers from waterlogging and frost damage by filling the lower area (about 20% of the volume) of the container with expanded clay and placing a planting fleece on top. This has the effect of preventing water and moisture from accumulating in the lower area and allowing it to drain properly through the expanded clay drainage. The fleece ensures that the soil cannot trickle down and muddy the drainage. Thus, the drainage holes are not still subsequently clogged and the terrace is not polluted.
It also makes sense to use a drainage system with expanded clay and fleece for indoor containers that are closed at the bottom. If, however, a little too much water is poured, the water collects separately from the roots in the lower area. With this type of planting, we also recommend using a moisture meter to determine when watering is needed again.
When do I need a new pot?
When the plant is getting too crowded
It then starts to push the soil out of the pot with its roots. Or the roots make their way down through the drainage holes and climb over the edge of the pot. Clay pots are simply blown away by the powerful root system and plastic containers are totally bent.
Other plants constantly get out of balance and fall over. They have grown so vigorously that their relationship to the pot size is no longer correct. How often houseplants ultimately need to be repotted depends on how much the plant grows, and is different for each species.
The plant could use fresh soil
This is the case when the soil is heavily compacted and absorbs little water. The water then often flows over the edge of the pot. The soil then stores little moisture and is poorly aerated.
In case of waterlogging
The soil is extremely wet, causing damage to the roots. In this emergency, the plant should be repotted quickly, regardless of the season.
What is the best time of year to repot?
Houseplants should ideally always be repotted outside of the dormant and flowering seasons. Therefore, the best time is either in the fall or spring.
How big should the new pot be?
If the plant is not already in the process of taking apart its pot, the new one should be one to two sizes larger. Then the roots will have enough space again. If the pot is too big, the houseplant would invest too much energy in its root system, at the expense of the flowers and leaves.
Which soil should I use?
In the trade, there is a special soil for almost every type of plant. However, these are only really useful for plants with very special needs, such as cacti, orchids, bonsai trees, rhododendrons, bog plants and potted plants. For most other houseplants, standard potting soil will suffice.
When do the plants need to be fertilized again after repotting?
With the fresh soil, the plants first get enough nutrients and are supplied for the next 4 to 6 weeks. If the soil contains a slow-release fertilizer, the next fertilizer application will not be necessary for about 6 months.
Repotting correctly – this is how it’s done
Repotting annual plants
Of course, the 2-year rule cannot apply to annual plants. These usually need to be repotted more often during the year, depending on the genus, in order to achieve optimal growth. This includes many summer flowers, most herbs and vegetables, especially if you grow them yourself.
As an example, we explain the advance on an enormously fast-growing tomato plant:
When growing your own, tomato seeds are usually placed in growing boxes or small pots in February or March. The germination period is usually quite short and takes place within a week. Once the first true tomato leaves develop about 2 weeks later, it is time to “prick” the plantlets. Pricking is a special kind of repotting, where a pricking rod (or simply a spoon) is used to carefully lift the plant and its roots out of the substrate. Then you can shorten the roots a little with scissors and plant the tomatoes individually and “lowered” in a larger pot (about 12 cm).
Another 4 to 6 weeks later, the pot will already be completely rooted and the plant will be many times larger. Now the tomato plant can be placed in its final location. Here is then repotted conventionally with the entire root ball. Depending on the tomato variety (dwarf tomato, bush tomato or stake tomato), the recommended pot sizes differ. Since a stake tomato grows particularly large and has deep roots, the volume of the pot should be at least 20 liters.
This example, with possible earlier or later planting times, can also be applied to other vegetables (for example, peppers, chili or cucumber).
Potting out and potting in
Repotting is not witchcraft and can be done in a few simple steps. By vigorously knocking and bumping against the old pot, you can loosen the root ball from the pot and lift out the plant together with the root ball. Loose soil can be removed. Then look at the roots. If they are white and strong, the entire root ball can be repotted. If there are few roots, or if they are brown, you must intervene. Loosen all the soil from the root ball and remove all damaged roots. In the new pot you should already fill the bottom of the drainage of expanded clay, as well as a fleece and some soil. On the bottom layer of soil you can now insert the plant. Pay attention to the height: the entire root system should be covered with soil! Please research the plant genus, whether it should be inserted rather higher or lower. Once the plant has been set at the correct height and straight, you can fill in the remaining soil. Lightly poke the pot with your hands to completely fill all the voids so that the plant is firmly in the pot. We recommend that you also cover the top layer with a fleece again and spread expanded clay on top. The fleece will prevent weed growth in the pot and the expanded clay will keep pests away. However, still leave a certain watering margin. This will make it easier to water the plant in the future. Depending on how wet or dry the new soil was when you filled it, water the plant vigorously.
Root pruning for trees and palms
With most trees and some palms in pot culture, it is possible and sometimes necessary to perform root pruning. This is done regularly in the bonsai sector so that the miniature trees can be kept for a long time in small and shallow containers.
Normally, root pruning can be combined with repotting in the case of trees. Extremely deep-rooted and fast-growing plants, such as the Canary Island date palm, tend to have such strong root growth that they can push the substrate over the edge of the container or the palm can push itself out of the pot from below. With larger specimens in tubs, as is common in parks and gardens, this can often be observed very well in the so-called “stilt roots”. These are the already woody roots, which have lifted out of the pot along with the trunk. In such cases, root pruning can hardly be done due to the size of the palm. However, if the palm tree is still a relatively manageable size, this is not a problem and absolutely does not bother the plant.
When you remove the palm from its existing pot, you will notice that there is no substrate or soil left at the bottom, as the deep roots are so strong that they have pushed the substrate upward in search of water. It is then advisable to cut or saw off this area of bare roots completely to be able to replant them properly. Despite the shortened roots, the new pot should definitely be somewhat larger than the previous one, so that the root growth can also go into the width.
In general, however, it is very important to research beforehand whether a particular plant can tolerate root pruning. On the other hand, there are also plant species with extremely sensitive roots, which do not easily forgive damage.
Should plants in hydroponics also be repotted?
Of course, plants in hydroponics should also be repotted, because the plants also outgrow the flower pot over time. The procedure here is very similar to when the plant is potted in normal potting soil. Hydroponics and thus also planters with irrigation systems are very popular, because here the care effort with watering is easier and above all more manageable. Water level indicators let you know exactly how much water is left in the planter and when it is time to refill it.