From the Digest

Grafting Cacti

By Eric Driskill (May 2010)

The writings of both Aristotle and Theophrastus demonstrated knowledge of grafting techniques and benefits. Aristotle wrote: “Some trees come into existence by being planted, some from seeds, others spontaneously. Those which are planted are separated either from the root, the stem, the branches or the seed, or else the whole is transplanted; some are slightly bruised before being planted. Some are planted in the earth; others are planted, that is, grafted on other trees. Grafting of one on another is better in the case of trees, which are similar and have the same proportions; the best results are obtained in the grafting, for instance, of apple on pear, fig on fig, or vine on vine. Sometimes grafting of different species is resorted to.”

Grafting is connecting or splicing two pieces of living plant tissue together. Grafting is done for several reasons, including:

  • To cultivate clones which are difficult by cuttings or asexual propagation.
  • To retain benefits of certain rootstocks.
  • To hasten fruit production or maturity and flowering for seed production.
  • To rescue a plant from disease or rot.
  • To grow a plant lacking in chlorophyll that would not survive on its own roots.

In grafting, you usually work with two plants. The plant that retains the root system is considered the rootstock. The plant grafted onto the stock is the scion. When grafting, you are trying to join the vascular tissues and vascular cambiums or vascular rings of the two plants.

The scattered vascular bundles of monocots prevent them from being grafted with any ease. In fact, I know of no successful grafted monocots. Dicots, on the other hand, have vascular cambium rings that lend themselves to grafting. These “rings,” which appear to be the cores of plants, are observed when you cut cacti to graft.

For a graft to succeed, meristematic tissue must develop between the stock and scion and differentiate into vascular tissues (xylem and phloem). After the plants have been grafted, the undifferentiated cells callus and grow from the vascular cambiums, which form a union between the stock and scion.

If the cells of the two plants are incompatible, the graft fails. With compatible cells, the intermingling union differentiates into vascular cambium and vascular tissue. The union between the stock and scion allows for the translocation of water, minerals, carbohydrates and other metabolites.

Cacti are typically grafted using a flat, cleft (V) or side technique. In a flat graft, both the stock and scion are cut. The edges of both cuts are then beveled, and the bottom of the scion is then joined with the top of the stock.

A cleft graft involves cutting a “V” groove into the stock and a similar cut to the bottom of the scion, and joining them together. A side graft may expose more of the cambium ring of each plant since it is cut at an angle, but may be more difficult to keep in place until the union is established.

For a flat graft, use a sharp sterilized knife or razor to cut the stock and scion. The edges of each should be beveled with the knife. The knife needs to be sterilized after each cut.

The scion is then placed on the stock in a way that assures the vascular cambium of each plant is in contact with the other. You do not want the vascular cambium of one to sit wholly within the vascular cambium ring of the other. Yet the cambium rings must be in contact, so you may have to offset the scion to assure they overlap.

After you affix the scion onto the stock, gently press on the top of the scion to make sure there is no air between the two plants. You then want to secure the scion onto the stock in a way that keeps it secure on the stock so the union can form between the two. For this you can use cactus spines, sterilized needles or pins, rubber bands, stretched pantyhose or weights.

Optimally you will want to leave the graft in a shaded area for several days without disturbing it. In a week or more you can remove what you have used to hold the plants together and very gently test to see if the scion feels like it has been successfully grafted. If not, you can try again, making a fresh cut on each plant.

The plant you wish to graft as the scion will dictate what stock you need to use. The two plants need to belong to the same family with a few exceptions. Some common stocks used to graft cacti are Trichocereus, Harrisia, Stenocereus and Hylocereus species. When grafting other succulents, do a little homework to find out what you can use as stock material.