How to Grow Cacti: A Detailed Guide to the Latest Growing Methods
Cacti have gone from growing in the wild to being widely brought into homes as cultivated plants, reflecting a trend among city dwellers in their choice of potted flowers. Because apartment space is limited and the air is relatively dry, large or more delicate potted flowers often grow poorly; it is most suitable to choose small, drought-tolerant varieties that are easy to care for yet highly ornamental, and cacti happen to meet all of these requirements.
How to Grow Cacti at Home
For growing cacti at home, it is best to choose small, free-flowering globe-shaped species. When cultivating them, do not assume that because these plants are drought-tolerant you can neglect normal watering and fertilizing. For indoor cultivation, you can use wire and plastic film on a windowsill to create a closed space with high temperature and high humidity; under such conditions most cacti not only grow quickly but also develop a lustrous color.
The potting soil should be a sandy or sandy loam soil that drains and breathes well and contains lime. Newly planted cacti should not be watered at first; simply mist them several times a day with a spray bottle. Only after half a month may they be given a small amount of water, and only after a month, once new roots have grown, can they be watered normally. In winter, when temperatures are low and the plants enter dormancy, watering should be restrained. After the beginning of spring, as temperatures rise, the plants gradually come out of dormancy and watering can be gradually increased. Apply a diluted, well-rotted liquid fertilizer once every 10 days to half a month; do not fertilize in winter.
Under ordinary residential conditions, by making full use of space, it is not difficult to grow dozens of pots of various cacti and set up a small “cactus garden.” At the turn of spring and summer, when the assorted cacti on the windowsill burst into a dazzling array of flowers, resting under such conditions after work not only relieves fatigue but is also an enjoyment of natural beauty.
How to Propagate Cacti
The methods commonly used to grow cacti are cutting propagation, division propagation, seed propagation and grafting propagation, four in all.
1. Cutting propagation
① Timing of cuttings: under normal conditions, May to June is the most suitable time for taking cuttings. Where a greenhouse is available, it can be done year-round.
② Preparing the medium: cacti are drought-tolerant and tolerate poor, thin soil, but hate waterlogging. Therefore the medium must have good air permeability, good drainage and the ability to stay moist; vermiculite and perlite are best. You can also make a mix of 4 parts coarse river sand, 3 parts loam, 2 parts leaf mold and 1 part rice-husk ash.
③ Cutting the slips: from a mother plant with strong growth and no pests or diseases, select vigorous, mature stem segments as cuttings. Use a rust-free scraper to cut the slips from the mother plant, and wipe and disinfect the tool with alcohol before and after each cut.
④ Drying the slips: freshly cut slips should not be planted immediately. First place them in a relatively dry indoor spot to dry for 5 to 7 days, and plant them only after the cut surface has dried and the stem flesh has begun to shrink.
⑤ Hormone soaking: for varieties that root with difficulty, soaking the base of the slip in plant growth hormone can greatly increase the survival rate. The method is: soak the base of the slip in a 50 to 100 ppm GGR (plant growth regulator) solution for half an hour to one hour, or soak the base in a 200 ml/L naphthaleneacetic acid solution for 4 hours. For most other varieties that root easily, hormone treatment is not necessary.
⑥ Planting the cuttings: bury the base of the slip shallowly in the medium; never bury it too deep, or it will rot. At this point the slip is hard to stand upright (because it has softened after drying), so you can lay it flat on the medium; you can also prop it up with a small stick, then gently press the soil on both sides of the slip with both hands so that it makes close contact with the soil.
⑦ After-planting care: first, water management. At planting time the medium should be moist; if it is too dry rooting is difficult, so you can pour a little water along the edge of the pot. But the medium must not be too wet, otherwise the slips easily rot. Before rooting, keep the potting soil moist at all times. To reduce evaporation, you can cover the pot with a plastic bag. After about a month the slips will root, and at that point the plastic bag should be removed at once. Second, light management. Before rooting, protect them from strong sun and keep them in a semi-shaded spot. After rooting, water and light can be managed routinely.
2. Division propagation: many cacti produce offsets. Globe-shaped cacti, for example, grow small offsets on the stem, while prickly pear cacti or segmented cacti all produce offsets. For these varieties we must take a little extra care: you can use a knife to cut off the growing point of the cactus, and after a period of cultivation many small offsets will grow near the growing point. When the offsets reach a suitable size, you can cut them off and propagate them as cuttings.
3. Seed propagation: the process of using seeds to propagate cacti is also very interesting, because only through seed propagation can you cross-breed new varieties yourself and give yourself some pleasant surprises. In seed propagation, pollinating the cactus flowers is the first step in the whole process, because most cacti cannot self-pollinate, so you have to play the “matchmaker” and lend them a hand. You can use a cotton swab to dab pollen onto the stigma, then quietly wait for good news. Before long, once the fruit is full and ripe, you can take out the seeds and wash them. Because cactus seeds are very small, it is best to wrap them in gauze and rinse them under running water; then scatter the seeds evenly over thoroughly moistened potting soil, place them in a dark spot, and keep the temperature at around 20°C; in winter the temperature must not fall below 10°C. When the seeds have developed into seedlings, you can carry out the first transplanting, then continue growing them in a dark place for a period before planting them out in small pots; alternatively, you can cut off the root system of the seedlings and graft them onto a rootstock.
4. Grafting propagation: grafting is a horticultural technique commonly used on cacti. Because the root systems of some cacti are very weak, after long cultivation the roots gradually lose their original function and disappear, and the plant consequently loses its vitality. Grafting is the panacea that saves these cacti. In addition, things such as speeding up a cactus's growth or keeping a plant with root rot alive after the affected parts are cut away can all be achieved by grafting. For grafting, the chosen rootstock - the triangular column - is one such cactus. The method is to cut off the growing point of the triangular column and bevel away the edges, then place the cactus whose root system has been removed in the center of the rootstock, and fix the position with string or a weight; after 1 to 2 weeks, the string and weight can be removed.
Pest and Disease Control for Cacti
1. Cabbage caterpillars and locusts: spray with a 2000-fold dilution of 25% deltamethrin.
2. Control of red spider mites: prevention should come first. The growing environment should be properly ventilated, but a certain humidity should be maintained, avoiding muggy heat and dryness. Commonly used chemicals include a 1000-1500 fold dilution of 40% omethoate and a 1000-fold dilution of 40% dicofol. In hot, dry seasons spray once every 7 to 10 days; spray thoroughly before overwintering.
3. Control of scale insects: because adult scale insects have a waxy shell on their bodies, chemical control often fails to achieve the expected results, so prevention should be valued even more. The growing area should be kept clean; when scale insects are found, they can be scraped off promptly with a bamboo strip, and branches with many insects can be cut off and burned. Chemical control of scale insects must seize the moment shortly after the eggs hatch and before the insects have grown their waxy shells, and repeated spraying is required for it to be effective. The chemicals usually used include a 1000-fold dilution of 50% malathion, an 800-fold dilution of 25% phosmet emulsifiable concentrate, and a mixture of 40% omethoate emulsifiable concentrate and 80% dichlorvos emulsifiable concentrate diluted with 1000 parts water.
4. White grubs, click beetles and cutworms: drench with an 800-1000 fold dilution of 50% phoxim.
5. Control of rot disease: preventing rot disease should be based on prevention. First, improve the environmental conditions of the growing site, which can greatly reduce the occurrence and spread of pathogens. Second, strengthen cultivation management. The planting soil should not contain any unmatured organic fertilizer, and fertilizer should be applied lightly rather than heavily. If waterlogging is found, drain it promptly; some of the damaged roots can be cut away, and the plant can be replanted after the wounds have dried. Regularly spraying fungicide on the cacti or the surrounding environment has a certain effect in preventing rot disease. Commonly used fungicides include zineb, carbendazim and thiophanate-methyl.
6. Golden spot disease, sunken spot disease and fusarium wilt: spray with a 800-fold dilution of 75% chlorothalonil, or a 600-800 fold dilution of 50% carbendazim or 70% thiophanate-methyl.
7. Rust disease: spray with a 2000-3000 fold dilution of 25% triadimefon.