Go forth and multiply (your plants)

Succulentophile is giving way this week to frequent guest columnist Peter Bangayan, whose article today scores the need to propagate our existing plants and help preserve species that are fast disappearing due in part to unscrupulous plant collectors.

Propagating your cacti and succulents is an exciting and rewarding way to increase your collection and there are many practical ways of propagating them. The most common form is raising your plants from seeds. Seed-raising cacti and succulent requires much patience because it takes considerable time for the seedlings to grow to mature sized plants, with some plants taking years or even decades to grow into impressive flowering-size specimens.

Seed raising is also an interesting way of growing plants because of the variability of the plants that can be obtained. Raising your cacti and succulent plants from seeds is easy if you follow guidelines concerning seed freshness, temperature, moisture, light, aeration and the medium. The most important factor in successful seed raising is having fresh seeds. Because many cacti and succulent seeds lose their viability fast, seeds that are kept in storage for a long time will most likely not germinate or will have a very low germination rate.

Another important factor is temperature. Seeds and seedlings need warmth to germinate and grow since we are in the tropics with year-round temperatures ranging from the mid-twenties to the low-thirties, so keeping the seeds and seedlings warm is not a problem. Seeds need moisture to be able to germinate. Too much moisture, however, will encourage the rapid growth of algae, bacteria and fungi. Algae can smother the seedlings and kill them while bacteria and fungi can cause the seedlings to rot. The right amount of moisture must be given to allow the seeds and seedlings to germinate and grow but not too much as to encourage algae, fungi and bacteria to multiply rapidly. Bright light but not direct sunlight is ideal for growing seeds and seedlings, direct sunlight can burn and desiccate the seedlings or make the medium dry out too fast that the seeds will not be able to absorb enough moisture to germinate.

Aeration is also an important factor because it keeps water from staying too long in the medium and on the seedlings, it helps control the moisture and keeps the growth of algae, bacteria and fungi in check. A good medium for seed raising is one that is well drained, can hold enough moisture long enough for the seeds to absorb water and germinate. It must also provide good root aeration to encourage growth and absorption of nutrients.

One such mixture that can easily be obtained from locally sold garden materials is a 50-50 mixture of coconut coir dust and sharp sand. The medium should be sterilized to ensure that bacteria and fungi, which can cause seedling rot, are destroyed or minimized. A shallow (about four-inch tall) clay or plastic pot is an ideal container for planting seeds but one must keep in mind that clay pots dry out much faster than plastic pots.

Here’s one rule of thumb: Seeds are planted in the medium to a depth of about one-fourth the size of the seed. They come in many sizes, from the fine dust-like seeds of Aztekium sp., some mammillarias or stombocactus species to large pea-size seeds of Calibanus hookeri, cyphostelma species or adenias.

Larger seeds are usually planted farther apart from each other while fine dust-like seeds are spread evenly onto the surface of the medium. A fine layer of coarse sand spread on top of the medium after the seeds are planted can serve to prevent the seeds and the medium surface from being washed away when watering the seed container. This layer will also act as an anchoring support for the seedlings once they germinate. The pots are then covered with fine mesh netting after watering to prevent the surface of the medium from drying out before the seeds are able to germinate. Place the seed pots in a bright place but away from direct sunlight to help the seedlings grow into more compact plants until they are able to take direct sunlight.

Watering the seed pots is a bit more tricky. Use a fine spray of water to avoid disturbing the medium and the seeds. The first watering should be thorough, meaning water should come out of the drainage holes of the pots. To know when to water again, remove the screen and examine the medium every day or two; if the medium is getting a bit dry on the surface, water with a fine spray to wet it. After a few days to about two weeks, the seeds should germinate if they are viable. When the seedlings have produced their first two pairs of true leaves or spines (in the case of cacti) the fine mesh netting may be removed. Water the seedlings when the surface of the medium begins to look dry, which is about in a month’s time. Watering with a very diluted fertilizer is recommended once a month because the coco coir and sand mixture have very limited nutrient value. When the seedlings begin to crowd the pot, they will be ready for transplanting into community pots or individual pots and can be treated according to your regular cacti and succulent culture. This may take about eight months for fast growing pachypodium and a number of years for slow-growing cacti such as strombocactus and aztekium.

Another practical way of propagating your plants is by offshoots. Many cacti and succulent plants – such as some species of echinopsis, mammillarias, gasterias, gymnocalyciums, haworthias, etc. – produce offshoots and these may be removed from the mother plant, dried out for a few days to allow callous to form on the cut portion and planted on their own. The offshoots will eventually grow into mature-size plants.

Other plants such as the columnar and branching cerei plants, euphorbias, monadeniums, etc. may be propagated by stem or branch cuttings. Another rule of thumb is that the cutting be made at the smallest cross section of the stem or the joint so that the "wound" will not be large, thereby lessening the chances of the wound getting infected by bacteria or fungi. The cut branch should be left out to dry in a bright, well-aerated place for about a few days to a week depending on the size of the cut made on the stem or branch. During this time, callous should form on the cut portion of the plant and the stem or branch will be ready for planting in your usual cactus mix.

Many plants such as adromischus, gasterias, haworthias, kalanchoes, pachyverias and sedums can easily be grown from leaf cuttings. With this method of propagation, a healthy succulent leaf is taken from the plant and the leaf is left out to dry for a few days for callous to form on the wounded portion. The leaf can then be planted into a regular cactus medium or better yet a 50-50 coco coir dust and sand medium, which should encourage the leaf to grow roots quite fast. After several months the leaf should produce one to several plantlets around the rooted area and these plants can then be separated from the leaf when they have grown large enough. With the offshoot, stem, branch, and leaf cutting method of propagation you get an exact genetic copy or clone of the original plant.

Other methods of propagation such as cell culture, tissue culture and meristem cloning techniques require specialized expertise, equipment and a laboratory – not exactly practical for the average hobbyist although these methods are often used by large commercial nurseries for mass propagation of valuable species.

There are many reasons to propagate your plants. First and foremost is to preserve the plant species; you can also exchange them for other plants or sell them to other collectors. Propagating plants can give the gardener great pleasure as you watch a tiny seedling grow into a mature-sized plant – or watch the miracle of a leaf producing a whole new plant.

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