You are repotting your cactus and noticed that it has rotten roots. The root tips seem to be dead, but you’re not sure what needs to be done. They need trimming, and here’s how I do it with my cactus for years.
To successfully trim any cactus roots it is necessary to 1) uproot the plant 2) clean the roots 3) trim the roots 4) dry and let the roots heal and finally 5) repot.
To prune or not to prune is sometimes a bit of debate among cacti growers. Here, I will discuss with you my personal experience with trimming off cactus roots. Let us start with the steps on proper trimming and aftercare.
Below you can find the 5 easy steps I have used for years to trim cactus roots.
The first step is to take off the cactus from its container. Tilt the pot and tap its side or squeeze it (plastic pot) to loosen the potting soil and the root system. When it’s all loose, gently slip out the plant and remove all the substrate from its roots.
Pro tip: You can place the potted plant under running water to soften and remove the plant from its container more easily. It will prevent further root damage and plant stress.
Once the cactus is out, it is best to wash off any traces of old potting mix. After washing, allow excess water from the roots to drip and dry out. With a paper tissue or dry towel, place the cactus on top and wait for 2-3 hours for them to dry.
Always make sure that no soil is sticking on the roots to avoid spreading molds and pests from the old soil. Checking the roots for any pest infestation is also a must. If the roots are infected with insects such as scales and mealybugs, get rid of them immediately.
Pro tip: To speed up drying, you can use an electric fan to blow them dry. I have a fan in my greenhouse, so drying can take up to less than two hours. Avoid exposing the roots to direct sunlight, or else they’ll end up withered and scorched.
When the roots are dry, start snipping off the small roots using sharp, sterile pruning shears. Dead, rotten, and crowded roots require removal. Trim off up to the healthy roots to promote root development.
For healthy but dense root balls, reduce the volume of the root system by cutting off the tiny roots such that there is more space for other roots to breathe and grow. Do not cut off a big portion of taproots or tuberous roots unless they are rotten or dead.
If planted on the ground, always leave at least 5 inches of the primary roots and 2 inches if potted. After pruning, dust the cuts with cinnamon or sulfur powder to inhibit pathogens and speed up wound healing.
Pro tip: Dead rotten roots are dark brown, hollow, and come off easily. Cut them down to the healthy root tissues to avoid further rooting. Dead roots are the favorite breeding place for molds and fungus.
Here is an excellent pruning tool.
Once all the roots that need trimming are removed, allow the cut to dry and heal for 5-7 days. Place the cactus in a clean tray and set it aside, away from direct sunlight and moisture.
You just cut your cactus’ lifelines, so it needs to heal and be callous. Root wounds will not heal faster if repotted right away. They may get infected, especially if planted on a wet substrate. This is the safe way to successful root trimming and should be practiced every time.
Pro tip: A bright filtered location with a good breeze will make the cut wounds heal faster. Totally healed and dried roots will have a lesser chance of rotting after replanting. It will produce new sprouts faster too.
After the trimmed roots are healed, it is time to replant the cactus to a fresh soil mix and a new container. Use a pot that is appropriate to the size of the cactus.
Always use a dry well-draining cactus soil mix when repotting your cactus. This will ensure new roots will not get damp when they start to develop and avoid early rotting. Be careful not to break any roots during repotting.
Place the newly planted cactus in a shaded bright area. Position it away from intense light as it slowly recovers and grows new roots. Water only after 10-14 days.
Pro tip: Wait for new roots to develop on the trimmed roots before repotting. On common cactus varieties, new root hairs will form after 5-10 days. When these tiny hairs start to appear, it is best to repot them right away so they will get in contact with the soil and develop faster.
Here is a quick and simple video tutorial on trimming cactus roots.
Cacti need root trimming as part of their maintenance in order to promote growth or address root diseases. In general, cacti need root trimming because of 1) too many roots 2) yellowing issues, and 3) removing old roots.
Just like all plants, cacti rely on their roots to continue living. So while you give maintenance for your cactus, like water, sunlight, fertilizers, etc., it is also crucial that you include root maintenance in your list.
Why should I cut off the roots of my precious plant? Here are the reasons why you need to prune your cactus roots.
Roots become crowded. Rootbound cactus will not reach their optimum growth but will stunt them instead. The existing roots cannot absorb water efficiently, and by pruning them, you encourage your cactus to grow new roots.
The base of your cactus is getting yellow. There are several reasons why your cactus turns yellow, and it is usually unpleasant. When a cactus gets yellow from the bottom, the problem should be on the roots. Probably, they are rotten and dead and need removal.
Upon repotting, there are dead old roots. You repot a cactus that has been planted on the same pot for several years and you noticed old and dead roots. So, whether you transfer your plant to a new pot or plant it in a landscape, it is wise to trim off its old roots to encourage future growth.
Cactus roots should not be trimmed when the cactus is 1) too small or still a seedling, 2) dormant, 3) not a good root grower, 4) soaking wet, and 5) mature and old. Trimming cactus roots requires careful consideration. It should be done only when necessary and when the life of the cactus is at stake.
Too small or still a seedling: Do not cut cactus roots if the cactus is too small or just a seedling because it will have a hard time developing new roots. This leads to stress and dehydration.
Dormant cactus: Inactive cactus will not develop new roots. It will have to wait until it grows actively again before new roots will form.
Not good root growers: Some cactus species do not root easily, such as Rebutia, Lophophora, and Astrophytums. Avoid trimming their healthy roots as they are not good root growers.
Wet cactus: Avoid cutting roots that are soaking wet. They require more time for drying and will be prone to rot.
Mature and old cactus: Do not trim the primary roots of mature and old cactus. They have spent several years developing them, and it will not benefit them being removed.
The advantages of cactus root pruning include 1) cacti growing new roots and having a healthy root system, 2) avoiding root rot and disease, 3) giving space to other developing roots, and 4) roots functioning efficiently. In contrast, root trimming can cause problems such as stress and root rot.
As long as trimming and repotting is done the right way, it will not harm the cactus in any way. Proper root trimming will get the cactus roots healthy and working efficiently. Here are the benefits that a cactus can get in root pruning.
New roots and a healthy root system. The main reason why growers trim their cactus roots is to encourage new root sprouts and develop a strong root system. Trimmed dead roots will have a chance to form new strands of healthy roots.
Avoid further root rot and disease. Once a cactus gets rotten roots, it will infect and spread to other roots until it gets on the base of the cactus. Trimming the rotten roots will stop the rot.
Give space to other developing roots. Rootbound cactus have overcrowded roots that compete on getting water and nutrients. Trimming and reducing their volume will allow other roots to grow and breathe.
Roots will function efficiently. Dead roots will no longer absorb water and nutrients. Removing them to develop new roots will make the root system effective and efficient in collecting and storing water.
Encourage new plant growth. Efficient roots can take up adequate water and nutrients needed for the growth of the plant. Having sufficient supplies of essential minerals will boost plant development.
Some cactus enthusiasts are afraid of trimming their cactus roots because they think it might kill their beloved plant. It will harm your cactus, actually, only if you’re doing the inappropriate methods. Below are the disadvantages of root trimming.
- Plant stress. Root trimming will cause pressure on the plant. Some cacti will get wrinkled stems due to days of drying after trimming.
- Root rot. Repotting right after trimming can get the roots infected by pathogens. Unhealed roots have open wounds that invite fungus to spread, leading to root rot.
- Trimming cactus includes uprooting the plant and cleaning the roots. When the roots are clean and dry, trim the tiny roots and let the wounds heal before repotting to new and fresh soil.
- Cactus needs trimming when it has overcrowded roots and yellowing base due to root rot. Cactus sitting long on the same container might need root pruning for fresh new roots to form.
- There are instances where cactus roots should not be cut, such as when a cactus is dormant or is already matured. Cactus that does not grow roots easily should not be trimmed.
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