How to repot cactus and succulent plants: in which period, how to proceed, which tricks to use

Alcune mie semine svasate

Some growers repot every year, while some others repot when required – i.e. when a plant shows signs of suffering or when the pot has become too small related to the stem. There can be many reasons for repotting (or racking, as someone says alternatively) a cactus or a succulent plant, and every grower has his own rules. As for me, I don’t have “fixed deadlines”: I evaluate plant by plant trying to understand if new soil and more space are needed. I repot my succulents when I see that the vase is now too small, when I believe that the soil has exploited or when I want to grow specific specimens more quickly. While it is true that many plants live quietly in the same container for five or six years (in many cases even longer!), it’s also true that frequent repottings (once a year or every two years) help to speed up the growth of cacti, particularly young plants and genera that over time take on considerable sizes, such as Echinocactus and Ferocactus.

I repot, also, when I notice that a plant has blocked for a long time and it doesn’t grow or produce new thorns. It can be the spy that something, at the root level, is going wrong. A plant that doesn’t grow or doesn’t swell despite watering, or, again, a plant that loses its colour (showing, for example, a lack of magnesium that not even fertilization can solve) can be saved by a repotting, with the cleaning of roots and the supply of new soil.

So let’s see in this article in which period it is better to repot cactus and succulent plants, which pots to choose (square, round, terracotta or plastic), how to check the roots and how to proceed in practice.

In which period to repot
Rinvasi di semine di Astrophytum capricorne
Repotting Astrophytum capricorne

Even the choice of the period to decant is personal: some growers repot at any time of the year and others repot only when the plants are in vegetative stasis, i.e. during the winter. There is no general rule and, from what I have observed, in general, any time of the year can be right. With one exception: I avoid disturbing the plants in the period from October to early December because the cacti in this period prepare themselves to dry and cold winter by reducing the internal water reserves. For this reason, I think it is more appropriate to let them do it without creating unnecessary traumas.

Generally, for practical reasons, I repot during the winter, from the end of December to March: in this period the plants are in vegetative stasis and have plenty of time to heal the wounds at the roots which repotting almost inevitably involve, before receiving the first watering (about mid-March). However, I have noticed that some genera, such as Gymnocalycium, if repotted during the winter, tend to speed up the deflation process. However, if repotted during the vegetative phase, they start again more easily and quickly. The same goes for seedlings and very young plants: that’s why I leave them at the end of my list and repot them in spring.

What is essential to understand, whether you repot cacti and succulent plants in winter, spring or summer, is always to wait a week or ten days after repotting before watering, to allow the roots to heal and minimize the risk of rot. For these reasons, some recommend leaving plants with roots in the air for several days before putting them in new pots. Personally, using dry soil for these operations, I do not find it necessary, except in two cases: when I washed the plant to remove all the old soil and when I had to cut the roots drastically because of some problems with the root system. In these cases, I leave the plants in a place protected from the sun for about twenty days.

Choose the right pot
Cartellini e vasi
Square plastic pots

Terracotta or plastic? Both materials have their merits and defects, and the choice should be consistent with the type of cultivation (abundant watering? frequent repotting? etcetera). In short, terracotta pots favour the rapid transpiration of water. If you use organic moulds the terracotta pot helps, but if you use mainly mineral moulds the plastic is much better because it allows the substrate to remain humid for a few days, giving the plant time to drink. The terracotta pot, if small, with a mineral substrate dries very quickly, and the plant risks not being able to suck the right amount of water before it evaporates. Also, for this reason, those who use terracotta pots tend to water more frequently than those who have chosen plastic.

How and when to water cactus and succulent plants.

Therefore, when you choose between plastic and terracotta, it is crucial to consider your method of cultivation, the soil, the time to devote to watering and many other factors. A good rule is to standardize the pots: all in terracotta or all in plastic to avoid different watering and cultivation regimes depending on the containers (which, when you have a certain number of plants, it can quickly lead you to a nervous breakdown!). Last note: in terracotta the roots inevitably tend to “cling” to the inner wall of the pots, while in plastic they do not find adherence. If you try to repot a plant that has been in a terracotta pot for at least four or five years, you realize that there is no alternative to the hammer – unless you want to lose hours of work, with exhaustion and swearing to remove the plant from the container.

Trichocereus svasato
Repotting a big Trichocereus

The size of the pot is relevant: for years we have been told that cacti go in small jars, at most one centimetre wider than the stem, and that with so much soil available the rottenness is just around the corner. False. Cactuses, like all plants, need much soil. The point is that the substrate must be correct for that particular plant species. If it is not very organic and if the substrate is well made and can dry quickly, there’s no reason be afraid: the plant can stay in an even very large pot. On the contrary, it has the right space to colonize and to absorb all the water available, without leaving “dead” areas perpetually wet. Many good growers are showing in these years that there is no sense (if not the aesthetic one, but de gustibus…) in favouring small pots or at the limit of the plant. On the contrary, working on landscaping, many growers have shown that cacti and succulents live very well even in oversized pots – provided, as always, that the substrate is correct.

For my plants I use plastic, square pots (because for the same size with round pots they contain larger volumes of soil, thus saving space on pallets), moderately oversized compared to the plant. I adjust myself according to the root system and the stem: in fact, the new pot should comfortably contain both the roots and the plant, possibly with all the thorns inside the edges of the pot.
For most plants, moreover, I use rather deep pots, so that the roots can develop well even in length, not only in width. From good practise, this becomes rule with taproot genus, such as Ariocarpus.

One more consideration: for the safety of the plant, always use new pots or used pots washed thoroughly with products such as bleach. I throw away the pots in which plants have died from fungal diseases such as fusarium.

Pests and parasites of cactus and succulent plants: how to recognize them.

The cleaning and root control
Gymnocalycium guanchinense svasato
Gymnocalycium guanchinense waiting for a repot

The repotting is an excellent opportunity to see “what’s underneath”. In short, to look at the roots. Once the plant has removed from the pot, it’s useful to check that the root system is in good condition, that there are no root cochineals or other pests (in that case, clean everything well, shorten the roots, throw the soil and treat the root system with specific products).
If the plant is already in my “standard” soil, I don’t break the soil bread: I shake it, remove some exploited soil, check it well and repot it in the same type of substrate. If instead, I have to change the substrate (for example because it is a plant that has just arrived in the greenhouse, or because I have seen that type of soil does not work rightly), I remove all the old soil, shaking away the inerts. Then I free the roots, control them, shorten them slightly and repot the plant in the new soil.

All of this has applied to healthy plants, of course. If instead, I see that the root system flakes because it is dry, I clean everything and cut the roots drastically, as far as I can see that the sap still passes. I have had more than one case of plants with the full root system compromised: in these cases, I cut all the roots up to the collar, leaving the plant at least a couple of weeks in the air; then I repot it in a pot at least a couple of centimetres wider than the plant itself, filled half with a usual substrate and the upper half with just pumice (or pumice and fine sand), which will help the rooting.

The cutting of roots, which some growers fear, is useful to give the plants a boost because of the restart. However, I never cut primary roots (unless they are sick), but only secondary ones and capillary roots. Also, never cut the taproot (unless it shows signs of rotting). For plants like Ariocarpus is useful a “thinning out” that leaves intact the taproot and its main branches.

Those plants in full peat deserve a separate discussion. Here the cleaning of the roots have to be total and accurate: the peat must be removed out of the way, possibly with a water jet, to free the root system. Once the plant has cleaned, let it dry for a couple of weeks in a shady area before repotting in the new soil.

The right soil for cactus: all my “recipes”.

Organize the work
Piante di mia semina appena rinvasate
Some of my plants after repotting

When you have many plants, it is good to have an organization. Usually, I identify the plants I want to repot and proceed by genus or type of soil. For example, I put together all the plants that go into compost based on field soil or all those that go into marl, all the sowing for which I use slightly more organic compost, etcetera. I keep available on the table various sizes of pots, tags, pencil to note the date of repotting (very useful data to get the situation under control and check if a plant is stopped too long or not), pliers, scissors and anything that may be useful to me, except for gloves. I don’t use them: I don’t want to give up the sensitivity of my fingers, which allow me to handle the plants gently, without breaking their thorns (I prefer to prick myself than breaking the thorns!). Only with very large and thorny plants (e.g. grusonii from 25 cm and up), I use a rag wrapped around the stem.

In the early years, I used to put a layer of expanded clay at the bottom of the vase, because that’s how I read in some manuals: some experts suggested to use it for doing the water drain better. It’s one of the things I abandoned over time. If the soil is correct, it will in itself be draining. And then, why reduce the soil available to the plant? Always for that belief that cactus roots and succulent plants would suffer from a sort of “underground agoraphobia”?
When I finish repotting, I add some soil around the collar (yes, just around the collar: contrary to what claimed for years). I do this to stabilize the plant, aware that after a couple of watering the substrate will drop considerably. As an alternative to the compost you can put some gravel (it’s useful when watering because it prevents the soil from going all over the place) or simple clayey soil, perhaps stretched a little with sand or quartzite. I like much the latter solution because it gives the plant a very natural effect, without having to work on the reconstruction of the habitat hunting for the right stones and the suitable sands.

Repot the seeds
Alcune semine svasate
My seedlings waiting for a repot

The repotting process does not change if the plants to be transplanted are seedlings. Here the only questions could be: repotting within the first year, after one year or more? Here, too, the observation is the golden rule: if the seedlings are too narrow and crowded together, I repot them even seven to eight months after birth. If, on the other hand, they have no space problems in their seed pot, I wait a year. Even if they are young, they don’t suffer. On the contrary, repotting helps them to grow faster. Even when I repotted seven months after sowing, I could see it: the seedlings started again immediately, they gained volume, and they spent their first winter in the same cold and dry conditions as the adult plants. The only trick: with sowing, it is good to use soil with a little organic fraction (peat); otherwise, you risk to see them deteriorate or get stuck.

General Considerations

Repottings generally help the plants to restart vigorously. However, it can happen that after a repotting (a traumatic event for a plant) a perfectly healthy cactus or succulent stops growth. It can happen, unfortunately. In that case, it’s better not to hurry, maybe move the plant in an area with filtered sun and keep it under observation. The new potting soil may not be suitable, or simply the plant needs some time before starting again. I had plants nailed after a potting season for up to two years. In some cases, I decided to do nothing because the plants were healthy; in other cases, I flared and found that the roots were dry.

To close, a useful warning: when you handle a thorny plant, it’s easy to prick or injure yourself. If this happens while you sink your hands into the soil, there is the risk of getting tetanus. Better to make sure you’re always in good standing with the relative recall!

You may also be interested in “How to fertilize cactus” or “How to make cactus and succulent plants bloom“.

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