How to Grow Cacti So They Become Plump and Robust? A Complete Guide to Care Techniques

Cacti belong to the Cactaceae family, perennial succulent plants with very tenacious vitality, able to grow even in tropical regions of Africa and desert areas, but to make cacti grow plump and robust, you still need to master the relevant cultivation techniques, so how do you grow cacti to make them plump and robust?

Cacti originate from the subtropical regions of the Americas in Brazil, Argentina, Mexico and subtropical desert or semi-desert areas, with a few produced in tropical Asia and Africa. They are also distributed in China as well as India, Australia and other tropical regions. In China they are mainly distributed in South China and Southwest China. Cacti are suitable for pot cultivation, and can also be planted in the ground in tropical regions.

Temperature requirements

The suitable temperature for the growth of cacti is 20-30°C, with a maximum not exceeding 35°C and a minimum not lower than 5°C. In winter, maintaining a temperature above 5°C is enough for safe overwintering, and the drier the potting soil, the more cold-resistant they are. Winter temperatures should be relatively stable; too great a difference between day and night temperatures easily causes cold damage. When the spring temperature reaches above 15°C, growth begins; when the midsummer temperature reaches above 35°C, they begin to enter dormancy, and resume growth after autumn.

Light requirements

Cacti are sun-loving plants, belonging to the strong positive type, and only under conditions of intense sunlight can they produce brilliant flowers. Therefore, they should be given sufficient light, especially in winter when full light is even more necessary. Generally, tall columnar and flat-shaped cacti are more tolerant of strong light, and can be placed outdoors in summer without shade. However, smaller spherical species and general cactus seedlings should be given semi-shade, avoiding direct strong light in summer.

Watering methods

Although cacti are garden flowers that are relatively drought-tolerant, in cultivation and management you should still water and spray reasonably according to the differences in species, season and plant size, avoiding plant shrinkage and premature aging caused by excessive water shortage. The amount of watering should be proportional to the temperature; during the growing season from May to October, adopt moist management. In midsummer, when temperatures are high and evaporation is great, watering is needed every day, and the best time to water is in the morning and evening. In the rainy season, when air humidity is high and evaporation is low, the potting soil should be kept half-moist to prevent root and stem rot. From late autumn, as temperatures drop, watering should be reduced accordingly.

In winter, water must be strictly controlled, keeping the soil from becoming excessively dry; the lower the temperature, the more the potting soil should be kept dry. Generally water once every 1-2 weeks, in the morning of a sunny day, and be careful not to let water touch the stem of the cactus, otherwise it easily causes stem rot. From March to April, as temperatures rise, watering should follow the principle of alternating dry and wet, watering thoroughly when dry, to meet the cactus's need to break dormancy and resume growth.

Soil selection

Soil is where plants grow; most of the nutrients and water plants need are absorbed from the soil, so soil has a direct relationship with the growth and development of plants. Potted cacti generally require calcareous sandy soil or sandy loam with good drainage and aeration; soil that is excessively fertile or contains too much soluble salt easily causes root rot and damage.

The mixing ratio of the growing medium should also be adjusted in practical application according to differences in cactus species, plant size, climatic conditions and so on. For example, for young plants, which need large amounts of nitrogen fertilizer and water during the growing period, the proportion of leaf mold in the growing medium should be appropriately increased. In areas with more rainfall and high air humidity, the proportion of river sand can be increased to keep the potting soil well aerated and drained. Also, for potted cacti placed on outdoor balconies, where the potting soil moisture evaporates easily, the proportion of garden soil and leaf mold can be appropriately increased. Sometimes peat soil or carbonized rice husks are used to replace leaf mold, also with good results.

Fertilization methods

During the growing season, cacti need appropriate fertilization, which is especially important for seedlings and grafted plants with well-developed rootstock roots. For top dressing, liquid fertilizers such as fully decomposed soybean cake water, fish intestine water, rotten egg water, etc. can be used, and attention must be paid to concentration: too dilute has little effect, too concentrated easily burns the roots. The method for making liquid fertilizer in home cultivation is to put crushed soybean cake, fish intestines, etc. into a wide-mouthed bottle with a lid, add 2-4 times the amount of water, leave one-third of the bottle's upper part as empty space, and let it ferment; after decomposing, add water to the clear liquid from the upper part at 10-20 times dilution, and apply once every 15 days.

For some ground-dwelling cacti that prefer calcareous soil, lime water can be applied 2-3 times during the growing period to prevent acidification of the potting soil. The method is to add 1 liang of quicklime to 2 jin of water, stir thoroughly, and after dissolving and settling, use the clear liquid above for irrigation; this liquid can be reused multiple times with added water.

Transplanting and potting methods

In spring from April to May, when temperatures rise above 15-20°C and cacti begin to grow, it is the most suitable period for transplanting and potting. Transplanting and potting can also be done in autumn from September to October.

For pots used in potting, unglazed clay pots with good aeration are best. A few species with taproots, fleshy or bulbous types require deeper pots, while some cacti with poorly developed root systems can be planted in shallower pots. Pots that are too large often cause the soil to be too wet, while pots that are too small restrict root development; both are unfavorable to the growth and development of cacti.

For potted cacti, do not water for 2-3 days before transplanting, so that the potting soil dries out, making it easier to knock them out of the pot with the soil. After knocking them out, remove the old soil and dead roots from the lower part, and also cut off overly long and coiled roots. If rot is found, the rotted part should be completely removed until healthy roots are exposed. For larger wounds, wood ash or sulfur powder can be applied, and after the wound has dried a little, pot them up.

Cultivation methods and precautions

Before potting, whether the pot is new or old, it must be washed and wiped clean, and fully allowed to absorb water before use. The potting method is to first place broken pot pieces, gravel, shells, etc. at the small hole at the bottom of the pot, to a depth of one-fifth to one-sixth of the pot's depth. After transplanting and potting, place in a cool place; do not water at the time, and only water thoroughly once after several days, then gradually move to a sunny place. Those transplanted in spring should not be fertilized within half a month; those transplanted in autumn can only be fertilized the following spring.

Precautions for cactus cultivation

1. Young cactus plants should be repotted once a year. Mature plants do not need repotting every year. However, after a certain period, the nutrients in the pot tend to be exhausted, the root system fills the potting soil, or due to frequent watering the potting soil becomes hard and compacted, which is unfavorable for drainage and aeration and easily causes root rot. Therefore, generally repot once every 2-3 years. For fast-growing varieties, when repotting, the pot can be somewhat larger than the original; it is suitable if the original pot can fit into the new pot. During cultivation, the surface soil of the pot should often be loosened to keep the soil well aerated, which benefits root growth.

2. Plants that are kept in a certain degree of dryness and sufficient light in cultivation and management have lighter stem color and slower growth, but their areoles and spines are well developed, thick and robust, and beautiful. Plants often kept under high temperature, high humidity and poor light conditions grow rapidly, with soft stem tissue and bright color, but their areoles and spines are poorly developed and their color characteristics are not obvious; for example, red spines often turn blackish brown. Therefore, the amount of watering should also be adjusted according to the purpose of cultivation.

3. The water quality used for watering and spraying should be one that does not contain too much sodium chloride and other salts. Generally, rainwater and well water are both fine, but the water temperature should not be too low; it is best if it is close to the air temperature. Tap water should be placed in a vat for 1—2 days before use. If fish are kept at home, using fish tank water to water potted flowers is even more suitable.