A cactus graft joins 2 cacti so they grow as 1. The stock is the lower piece, which has or will grow the roots. The scion, on top, is the plant you want to grow. San Pedro (a Trichocereus) is a long-established grafting stock for rare or difficult cacti, and growers use it for rare Trichocereus too. Its small spines make it easy to handle.
The short version
- Graft in spring or early summer, while both plants are actively growing.
- Use a firm, plump stock. Water a rooted stock 1 to 4 days ahead; callus an unrooted one for about a week.
- Choose a scion under about 4 inches tall that will not hang past the stock's edge.
- Cut the stock across where its vascular ring (the circle inside the cut face) is about the size of the scion's. Bevel the edge and leave a thin cover slice on the face.
- Cut the scion flat, lift off the cover and set the scion down straight away: centered if the rings match, off center so they cross if the scion's is smaller.
- Hold it with 2 rubber bands at right angles, or tape. Keep it in bright shade, the join dry.
- Take the bindings off after 7 to 10 days. At 2 weeks, a scion that has taken is firm, plump and sealed at the edge.
- Once it has taken, pot an unrooted stock. Give an unrooted cutting no water until it has rooted. Rooting takes 4 to 8 weeks.
What you need
- A thin, sharp knife with a smooth edge, 70% isopropyl alcohol and a cloth.
- Rubber bands that reach over the scion and under the stock, or tape or an elastic bandage.
- Cactus gloves or a strip of folded cardboard, small scissors, and a pen to label the stock.
When to graft
Graft in warm weather, while both plants are actively growing. Spring grafts tend to take better than autumn ones. An unrooted stock (a cutting with no roots yet) needs about 2 weeks for the graft to take and 4 to 8 weeks to root. Cuttings generally root well while nights stay at 60 F or warmer, so leave 6 to 10 weeks of that weather.
Choosing the scion
Collectors use 3 kinds of scion:
- A tip is the top of a stem, with its growing point.
- A puck is a short section from the middle of a column. With no growing tip, it grows pups (new shoots) from its areoles, the pads the spines grow from.
- A slab is a thin cross-section of a column; 1 column makes several. Collectors usually keep a slab at least 1 inch thick, as thinner ones can dry out and fail.
Growers suggest a scion under about 4 inches tall, since a taller one needs more pressure to hold down. It can be narrower than the stock but not noticeably wider, since growers find an overhanging edge can dry out and lift away. Snip off any spines at the scion's base that would dig into the stock.
Preparing the stock
Hydrate first. Growers look for a firm, plump stock, not a wrinkled one. A common practice is to water a rooted stock well 1 to 4 days ahead and graft it in its pot. An unrooted cutting gets no water, so choose a firm one.
Callus an unrooted stock. About a week ahead, lay it in a shady, airy place so the cut end can callus. A callus is the dry skin that forms as the soft inner tissue of the cut dries over.
Mid-sections. Some growers use a mid-section as stock, such as a San Pedro mid-section cut for grafting. Keep it the way up it grew: callus and root the lower end, and graft on the upper end. To tell the ends apart, see which way up a cactus cutting goes.
Set everything out first. A smooth graft takes about 45 seconds, and neither cut face should sit open to dry air.
- Clean the blade. 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. Repeat between grafts.
- Cut to match the rings. Inside the cut face is the vascular ring, the tissue that carries water and food through the stem. The scion's ring must touch the stock's ring for the graft to join. A San Pedro widens below its tip, so cut straight across where the stock's ring is about the size of the scion's: close to the tip for a small scion, farther down for a large one. If the ring is still smaller than the scion's, slice again a little lower.
- Bevel the edge. Trim the ribs and skin around the cut at a slant, about 1/4 inch off the outer edge all round. Cut flesh shrinks as it dries, and the bevel stops the outer edge from lifting the scion. Growers sometimes skip it on a first graft and keep the spines at the top edge to hook tape onto.
- Make the second cut. Slice a thin layer just below the first cut and leave it on the face as a cover, to keep it from drying while you cut the scion.
Making the graft
- Cut the scion. Make 1 straight, flat cut across its base. On a puck or slab, growers usually take a fresh thin slice off the lower face too. Both faces must be smooth and flat.
- Join them. Lift off the cover and set the scion in its place in 1 movement. If the rings are about the same size, center the scion by eye from above. If the scion's ring is smaller, growers usually set it off center so its ring crosses the stock's ring on 1 side; a small ring set in the middle of a wide one does not touch it. Do not spend time lining it up. Press gently, twisting a little back and forth to push out air.
- Hold it. Stretch a rubber band over the scion and under the stock (under the pot for a rooted stock, under the callused base for an unrooted one), then a second at right angles, so the pressure is even. A common alternative is tape or an elastic bandage, stretched over the scion and hooked on the stock's spines. Hold it firmly, without denting it.
- Label it with the scion's name.
The first 2 weeks
Set the graft in bright shade, out of direct sun, and leave it alone. Growers keep the join dry until it seals, watering a rooted stock at the soil only. Remove the bindings after 7 to 10 days and check the graft at 2 weeks.
Telling whether it has taken
- It has taken if the scion is firmer and plumper than when grafted and the join is sealed at the edge, with no gap.
- Watch it if the scion is shrinking or its top is sinking in the middle, a sign it is drying out. If it keeps shrinking, the graft has probably not joined.
- It has not taken if the scion comes away, sits loose, or the join shows mold or rot.
For a failed graft, the usual fix is fresh cuts on both pieces and another try. A graft can look good at 2 weeks and still fail, so keep checking it until the scion puts on new growth, which may start within a few weeks in warm weather and shows the graft has joined.
Rooting an unrooted stock
Once the graft has taken, pot the stock as you would to root a cactus cutting. Use dry, gritty cactus mix in a pot with a drainage hole, a little wider than the base. Set the base just deep enough that it stands firmly without rocking. Keep it in bright light out of direct sun, with nights at 60 F or warmer. Give an unrooted cutting no water until it has rooted. Rooting takes 4 to 8 weeks.
Later, shoots from the stock's lower areoles compete with the scion; removing them is part of caring for grafted cacti.
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
Does Grafting Time Affect the Cactus Performance? Neda Bayat, Roohangiz Naderi and Ardeshir Rahimi Maidani, Journal of Biological and Environmental Sciences 9(27):143-149, 2015. https://dergipark.org.tr/en/pub/jbes/article/1674713
Studies on Inter-generic Grafting Compatibility of Ornamental Cacti. R. Perumal, M. Prabhu, M. Kannan and S. Srinivasan, 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
Physiological Study of Graft Union Formation in Cactus: II. Role of Auxin on Vascular Connection between Stock and Scion. Takashi Shimomura and Kenzo Fuzihara, Journal of the Japanese Society for Horticultural Science 45(4):397-406, 1977. https://www.jstage.jst.go.jp/article/jjshs1925/45/4/45_4_397/_article
Grafting Types, Cactus Grafting. Plant Propagation, University of Florida IFAS with the University of Kentucky and Texas A&M University, 2023. https://propg.ifas.ufl.edu/06-grafting/02-graftingtypes/05-grafting-cactus.html
Cutting Terminology, Polarity. Plant Propagation, University of Florida IFAS with the University of Kentucky and Texas A&M University, 2023. https://propg.ifas.ufl.edu/05-cuttings/01-terminology/08-cuttingterms-polarity.html
How to Propagate Agaves and Cacti from Cuttings and Seed. Jack Kelly, University of Arizona Cooperative Extension, 2009. https://extension.arizona.edu/sites/default/files/2025-03/How-to-Propagate-Agaves-and-Cacti-From-Cuttings-and-Seed.pdf
Plant Disease Pointers, January 2022: Decontaminating Your Way to Healthier Plants. Plant Disease Diagnostics Clinic, University of Wisconsin-Madison, 2022. 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