Cactus (Part 3) - Propagating Your Cactus
 

Most people who grow cactus plants eventually want to increase their collection through propagation. In most cases, propagation of cactus is quite easy. Seeds, cuttings or division can all be used to propagate these plants, with the best method depending on the type of plant.

Cactus from Seed

Propagation by seed is an inexpensive but slow way to introduce unusual and exotic cacti to your collection. Nurseries, mail- order houses and specialized cactus societies usually have cactus seeds available at a relatively low cost. Seed may also be collected from any cactus plant that has flowered either in your home, or in nature, by simply removing the ripe pods. Fully mature pods should be cut open, and the seeds squashed out onto a piece of paper towel where they can dry at normal room temperature. Rapid drying of the seeds will reduce the chances of rot occurring. If you plan to store the seeds for any length of time, they must be fully air-dried before being placed in storage.

Early spring is the best time to sow cactus seed. This is because seedlings that germinate in springtime have the benefit of summertime light levels in which to establish themselves. A small pot (5 cm) or shallow pan is ideal for germinating the seeds. Whatever container is used, it should be filled nearly to the top with rich, free-draining cactus soil. After firming the growing medium, seeds can be evenly spread on top. The seeds can then be covered by sifting a very thin layer of sand over top of them. The layer of sand should be very thin, and should permit at least a small amount of light to reach the seeds. The newly sown seeds can then be watered by sitting the pot in a shallow tray of water until the top of the growing medium has become moist. You may wish to add a fungicide such as No-Damp to the water to help reduce the incidence of damping-off. After the pot has been permitted to drain completely, it can be covered with a clear plastic bag, and placed in a location that receives bright light, but where there is no direct sunlight. Direct sunlight will result in a rapid heat build-up in the bag, and could easily kill the delicate seedlings.

Depending on the species, seedlings can be expected to emerge over a period of 2 to 16 weeks. If a mixture of seeds was planted in the same pot, it is best to wait until no new seedlings are seen emerging before disturbing the young plants. Once several weeks have passed with no new seedlings emerging, the plastic bag can be removed, and a bit more sand sifted over the seedlings to provide them with better support and reduce the chances of damping-off. The seedlings should not be introduced to full sun for at least one year.

As long as the seedlings are not crowding each other, it is probably best to leave the young plants in the original pot. Plants should be placed in individual pots only once they have begun to crowd one another. Newly potted seedlings should be kept in a cool location with bright light for several weeks. After this time, they can be slowly introduced to brighter and brighter light, until they are growing in a location with full sunlight.

Cacti from Cuttings

Propagation of cacti through cuttings provides larger plants much more quickly than propagation from seed, but far fewer plant can be obtained. Those types of cacti that are columnar, pad-forming or those with segmented stems such as a Christmas cactus are easily started from cuttings. As with seed, spring is the best time to take cuttings, as most cacti will be emerging from their winter rest at this time and initiating new growth. The size of the actual cutting taken can be quite variable. On a Christmas cactus, a couple of stem segments may be used, with a total length of a few centimetres, while on some columnar cactus plants, a single cutting may be as long as a meter. An important point is that the plant that you are taking the cutting from should be in as healthy a condition as possible.

When taking a cutting from a stem section, use a clean sharp knife. If you are taking several sections from one long stem, you must remember which was the top and the bottom of each piece, because a stem piece that is planted upside down will not grow. A simple way of keeping track of the top and bottom is to cut the bottom of each segment on a slight angle, and the top straight across. For pad-forming, or branching cacti, the cuttings should be taken at the joints so that the mother plant is not significantly disfigured. A single oval pad from a pad-forming cactus makes an ideal sized cutting.

The primary problem encountered with cactus cuttings is the development of fungal soft rot. This condition begins at the cut surface and eventually reduces the entire cutting to a slimy mass. Two techniques are recommended for avoiding this problem. The first is to simply allow all fresh cuttings to sit in a warm dry place for from 1 to 14 days before they are placed in the rooting medium; the larger the cut surface, the longer they should be allowed to dry. During this time, the cut moist surface will form a dry callus which is far less prone to rot. Although it sounds slightly alarming to leave a newly taken cutting sitting exposed for several days, remember that a cactus is able to survive periods of drought. As long as the cutting is not noticeably shrivelled, it is probably alright to leave it dry. Newly cut stem segments may also be dipped in garden sulphur before planting to prevent the onset of soft rot.

Cuttings will root in a standard well-drained cactus mixture if provided with bright light and cool temperatures for several months. Although the cuttings may not have a developed a root system, resist the temptation to keep their soil any wetter than you would a normal cactus plant. The wetter the soil, the more likely the cuttings will rot.

Division

Division is an ideal method of propagating those types of cactus which bud off new plants from the side of the mother plant. These offsets usually already have roots developed and need only be carefully pulled or teased away from the parent plant and placed in a pot of their own. The advantage of this type of propagation over the taking of cuttings is that division leaves the mother plant with almost no signs of disfigurement. Where cuttings are taken from non-branching types of cactus, the mother plant is often left in an unattractive condition.

© 1995 Erl Svendsen
(Permission requested for reprint)

Cacti are Succulents
Growing a Healthy Cactus
Propagating Your Cactus
Cacti and Succulents
Growing Cacti