Repotting - when and how to repot indoor plants?

Reasons why we do repotting:

• Root bound - as the plant grows, the roots occupy more and more of the available space in the pot. In the short term, the plant is not significantly affected (some plants may even have better vegetative growth when they are root bound), but in the long term, there may be some problems: the plant may slow down or stop growing, the substrate might no longer retain enough water and nutrients (thus, more frequent watering and fertilizing is necessary). The phenomenon can have multiple causes - sometimes plants come in undersized pots for more efficient transport, other times they simply have a very fast growth rate and require more frequent repotting into new culture pots. However, there are plants that do very well and have spectacular vegetative development when they are at a certain level of root bound - a few examples: hoya, some orchids (epiphytes), Spathiphyllum, most ficus species, the majority of succulents and cacti, ferns, philodendron and epipremnum, etc..

The root bound condition does not require an immediate pot change - if the plants look good and have proper vegetative development, replanting can be postponed until the appropriate season (growth season). There are several levels of root bound, and seriously affected plants show clear signs when urgent replanting is necessary: dehydration, wilting, leaf drop, etc..

• Unsuitable substrate - each producer uses their own formula for substrate, adapted according to several factors: growth system, watering system, general conditions in the greenhouse, growth performance, etc. In some situations, the substrate may be considered unproductive for the microclimate in our homes or incompatible with our watering habits. In this situation, we will make an evaluation and determine if and how urgent a possible substrate replacement is.
• Root rot - the plant has rotten roots and begins to deteriorate. Causes can be multiple, and this scenario is usually encouraged by improper watering habits for the species and/or microclimate and/or a substrate unsuitable for the microclimate or growth style. Sometimes, plants can arrive at this stage after long international transports and temperature differences in the distribution/logistics chain, or they can reach this stage when we try to accommodate (adapt) plants to a new environment significantly different from the one in which the plant was grown. It is not a reason to panic, but if the plant is significantly affected, changing the substrate, disinfecting or changing the pot, and removing damaged roots as soon as possible is necessary.

Replanting, depending on the seasons

• spring - is the best option. The day lengthens, temperatures naturally rise, and plants resume growth. This season is the most favorable for the rapid development of a healthy root system.
• summer - replanting will be done with increased attention to watering (more frequent watering), without subsequent exposure to the sun. Plants will be kept in cool spaces to avoid additional stress caused by high temperatures.
• autumn - repotting can only be done for certain types of plants, when the day is still long enough and we know the species well enough to anticipate its further development.
• winter - only urgent or minimally invasive replantings will be done. For successful replanting this season, it is necessary to place freshly moved plants in a space as bright as possible, properly heated. Ideal temperatures for root system development: 20-22 degrees. Above 23 degrees, the development of pathogens is favored, which can irreparably affect a sensitive (freshly moved) plant. Avoid placing freshly moved plants near a "cool" window - the temperature near the glass can be up to 4-5 degrees lower (than the rest of the room). Avoid placing freshly moved plants near heat sources (radiator, heated floor, etc.).

How do we determine if replanting is necessary?

Plant evaluation. If we find that the plant looks bad - signs of weakness, unusual coloration, dehydration, atypical growth, etc. - we will proceed to remove the plant from the pot. Usually, it is enough to gently press the pot all around and pull the plant out while keeping the "ball" of substrate intact. In advanced root bound stages, it is necessary to cut the pot to extract the plant (we should make sure we have pots of similar sizes before this operation).

Root evaluation. After removing the plant from the pot, the roots will be visible. If we observe only a few damaged roots, we will try to remove them without disturbing the plant too much. If the roots are very affected (over 50%), it is necessary to remove them, replace the substrate, and replant. The presence of some degraded roots is normal and natural for most plants, both in nature and in cultivation conditions.

Substrate evaluation. After removing from the pot, substrate evaluation becomes easy. We will observe what materials the substrate is made of (we will consider the composition, related to our watering habits and microclimate), if it is decomposed and if there are fungi/molds (and in what proportion). Most fungi and molds in the pot are harmless to plants (not pathogenic), but their massive presence indicates a degraded substrate, possibly too acidic (due to decomposition) for sensitive plants. A degraded and acidic substrate can be a good host for specific pathogens (soil borne diseases) - root rot, sclerotium, fusarium (extremely rare), phytium, rhizoctonia, etc..

How do we do the replanting?

Choosing the pot. For a healthy plant, the new pot will have a diameter only 2-3 cm larger. For an affected plant, where it was necessary to remove a significant part of the root system, we will use a similar or smaller pot, but capable of supporting the plant.

Selectia de ghivece disponibile la Secret Garden (link).

In the case of plants that lose their root system or have an insignificant number of roots, we will use specific regeneration methods (e.g., a bed of sphagnum moss, rooting in a bag, etc.). Before cutting the plant roots, we will research and make sure their appearance is not appropriate - usually damaged roots have a color (black or brown) and a specific texture (soft, juicy, or completely dry). We will NOT cut firm roots, regardless of color.

Choosing the substrate. The substrate will be chosen based on the species and its needs, taking into account our usual watering habits, the time we can dedicate to plant care, and the microclimate in which we will grow them. As a general rule, it is preferable to use a well-drained substrate, but with some water retention, so that watering can be done at a reasonable interval.

Inorganic substrate and hydroponic culture. It eliminates or limits risks associated with pathogens, but water and nutrient retention are key words when thinking about choosing a substrate or a cultivation method. Using inorganic substrate (LECA/clay balls, perlite, etc.) requires more maintenance and increased attention to the plant's needs (special nutrients are used for hydro cultures, adapted for each plant type), depending on the setup used.

Selection of substrates and raw materials available at Secret Garden (link).

Replanting with minimal intervention. Each plant is alive and develops a root system aimed at nourishing and stabilizing it in a position that will allow it to absorb the necessary light through its leaves. Moving a plant is a delicate operation that requires a lot of care, as roots can be brittle (easily broken), and the plant can thus be destabilized. If the roots and existing substrate are in good condition, it is sufficient to remove the plant from the old pot and replant it in the new pot, filling in with substrate.

Removing the old substrate. Place the pot in a container with lukewarm water - after about 10 minutes, the substrate will be soft, moist, and easy to remove. If difficulties arise (especially in the case of root bound), a low-pressure water jet can be used to remove substrate residues between the roots.

Fungicide application. When replanting, it is recommended to use a broad-spectrum fungicide to prevent the development of pathogens. Application can be done by dipping the pot in the prepared solution until the substrate absorbs a sufficient amount.

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