A grafted cactus is 2 plants growing as 1. The lower plant, the stock, keeps the roots. The plant on top, the scion, is fed through the join, the place where the 2 grew together. San Pedro (a Trichocereus) is a common stock.
The short version
- If you made the graft or it still has its bands on (the rubber bands or tape that hold a new graft together), start with "The first months after grafting". If your plant is growing in a pot with the bands off, start with "Removing stock pups".
- Keep a new graft in bright light with some shade until it has taken and rooted. Growers usually keep water off the join until it has sealed, with no gap at the edge.
- Give an unrooted stock or scion no water until it has rooted. Rooting takes 4 to 8 weeks.
- Remove every shoot that grows from the stock, below the join, as soon as you see it. Shoots from the scion stay.
- Once rooted, grow it like any San Pedro. In winter, protect it for whichever half is less hardy. For San Pedro, start protecting at 28 to 30 F, earlier for pots and in wet winters. If you do not know what the scion is, protect it before the first frost.
- Every stock wears out in time. Watch for shriveling, yellowing or softening below the join.
- Taking the scion off (degrafting) is optional. Do it when the stock is failing, when the scion is getting too heavy for the stock, or when you want the stock to pup again. Then root the top, or graft it onto a new stock.
- A variegated scion with clear patches of green can often grow on its own roots. One with little green is generally kept grafted.
The first months after grafting
Bands generally come off after about a week. By about 2 weeks the scion should look firmer and plumper, and the edge of the join should look closed, with no gap. A scion that shrinks or turns concave (sunken in the middle) is a warning sign, and one that comes loose has not taken. Some grafts look firm at first and still fail later, so keep checking for a few more weeks.
Keep it in bright light with some shade, such as the dappled shade of a tree, until it has taken and rooted. Then move it into more sun gradually over a few weeks; see acclimating a cactus to sun.
On a rooted stock, water the mix at the base, not the plant, so the join stays dry. If the stock had no roots when grafted, pot it once the bands are off, as you would any cutting. Give an unrooted cutting no water until it has rooted. Rooting takes 4 to 8 weeks, and goes best when nights are about 60 F or warmer.
Removing stock pups
A pup is a side shoot. The stock can make pups from its areoles, the small felted pads that carry the spines. A pup on the stock draws on the nutrients the stock supplies to the scion, and one close to the join can press against the scion as it grows and push it off.
Telling stock from scion. Anything growing from below the join comes from the stock. A shoot from a San Pedro stock has the same short, sparse spines as the column it grows from. Pups from the scion are what many grafts are made for, and they stay.
When. Look over the stock each time you water while the plant is growing. Remove a pup as soon as you can see that it sits below the join.
How. Wear cactus gloves, or hold the plant with a folded strip of cardboard. Growers often pop a small, soft pup off with a thumb. Cut a larger one off where it meets the stock. Viruses can travel on blades. Wipe off any sap and dirt, then wipe the blade with 70% isopropyl alcohol so it stays wet for at least 30 seconds. Let it air dry. Leave the wound open to the air, and keep water off it until it is dry and hard.
If you want an extra plant, some growers let a stock pup grow, then cut it off and root it; see taking cactus cuttings.
Light, water and winter
A rooted grafted Trichocereus generally needs the same care as any San Pedro: strong light, and water only when the mix has dried out; see watering cactus.
The scion may not stand the same cold as the stock, so growers usually protect a graft for whichever half is less hardy. For a San Pedro stock, start protecting at 28 to 30 F, earlier for pots and in wet winters. If you do not know what the scion is, protect the plant before the first frost. Protecting means a dry plant under cover or indoors; see cactus winter care.
Signs the stock is wearing out
How long a San Pedro stock lasts varies; it generally outlasts other stocks, and every stock wears out in time.
Below the join, shriveling that does not plump up after a thorough watering, yellowing, or softening while the scion stays firm may mean the stock is failing. Soft tissue that is also dark and wet is rot; deal with it the same day, as in cactus rot. Degraft while the scion is still firm.
Degrafting and regrafting
Degrafting means cutting the scion off its stock; regrafting means putting it onto a new stock. A healthy graft does not have to be taken apart.
Reasons to do it.
- The stock is failing.
- The scion is getting too heavy for the stock and starts to lean.
- You want more plants. A stub of scion left on a healthy stock tends to pup again, and the top you cut off becomes a plant of its own.
- The scion is big enough to grow on its own roots. Some growers wait until it is at least 8 to 12 inches long.
How. Do it once nights stay at about 60 F or warmer, so the top can root soon after. Wear cactus gloves, use a disinfected blade, and steady the scion with your gloved hand as you cut. On a healthy stock, a common practice is to cut through the scion and leave a few inches of it on the stock. That stub stays grafted and tends to pup again from its areoles; collectors often leave a longer stub to get more pups. Keep removing pups from the San Pedro below it. On a failing stock, cut the scion off just above the join.
Root or regraft. Root the top if it has enough green to live on its own. Regraft it onto a fresh stock if it has little green; how to make the graft is in grafting onto San Pedro.
Re-rooting the scion
Set the scion in bright light with some shade, in moving air, with the cut end open. Give it no water. It is ready to plant when the whole cut face is dry, firm and sealed, with no damp or soft spots when you press it lightly. That takes several days or more, and a common practice is to wait about 2 weeks.
Then plant it cut end down in a gritty, fast-draining mix; see cactus soil and how to root a cactus cutting. Water it only once it has rooted, 4 to 8 weeks later.
Variegated Trichocereus
The yellow or cream patches of a variegated plant have little or no chlorophyll, the green pigment a plant needs to make its food. Collectors often degraft a variegated Trichocereus with clear patches or stripes of green, and it can then grow on its own roots. One with little green is generally kept grafted. A scion with no green at all cannot live on its own roots; the moon cactus is the familiar example.
A variegated scion is prone to sunburn. Collectors usually grow one in bright light but out of strong direct sun, with extra shade on the hottest summer days.
Sources
The Double-Cut Technique for Grafting Cacti to Trichocereus pachanoi Rootstock. Dan Bach, Desert Plants 3(1), 1981 (reprinted), University of Arizona. http://hdl.handle.net/10150/556561
Studies on Inter-generic Grafting Compatibility of Ornamental Cacti. R. Perumal, M. Prabhu, M. Kannan and S. Srinivasan, Tamil Nadu Agricultural University, International Journal of Current Microbiology and Applied Sciences 9(11):2133-2144, 2020. https://www.ijcmas.com/9-11-2020/R.%20Perumal,%20et%20al.pdf
A brief review of plant diseases caused by Cactus virus X. Edzel Evallo, John Darby Taguiam and Mark Angelo Balendres, Crop Protection 143:105566, 2021. https://www.ukdr.uplb.edu.ph/journal-articles/32
How to Propagate Agaves and Cacti from Cuttings and Seed. Jack Kelly, University of Arizona Cooperative Extension, AZ1483, 2009. https://extension.arizona.edu/sites/default/files/2025-03/How-to-Propagate-Agaves-and-Cacti-From-Cuttings-and-Seed.pdf
Grafting Types, Cactus Grafting. University of Florida, University of Kentucky and Texas A&M University, 2023. https://propg.ifas.ufl.edu/06-grafting/02-graftingtypes/05-grafting-cactus.html
Cacti and succulents. Deborah L. Brown, University of Minnesota Extension, reviewed 2026. https://extension.umn.edu/houseplants/cacti-and-succulents
Decontaminating Your Way to Healthier Plants. Plant Disease Pointers, January 2022. Plant Disease Diagnostics Clinic, University of Wisconsin-Madison. https://pddc.wisc.edu/2022/01/27/january-2021-decontaminating-your-way-to-healthier-plants/
Clean and disinfect gardening tools and containers. Julie Weisenhorn, Natalie Hoidal and Annalisa Hultberg, University of Minnesota Extension, reviewed 2026. https://extension.umn.edu/planting-and-growing-guides/clean-and-disinfect-gardening-tools