Growing lithops at home is an uncomplicated task if the natural cyclical growth of the plant is taken into account. Lack of knowledge about the succulent's biology leads to improper care and, consequently, its demise. The unusual annual growth cycle of lithops consists of four periods, each corresponding to its own rules of care and watering: growth period, dormant period, flowering period, and renewal period. The most crucial factor for keeping lithops is proper watering in accordance with the periods of its life cycle.
During the dormant period from June to August (in nature, the dry season with long daylight hours), lithops does not grow, does not bloom, and sometimes sinks completely into the ground. At this time, while in the dormant period, the plant needs no watering and uses moisture accumulated during the growth period. In case of leaf wrinkling, gentle moistening of the top 1 cm (0.4 in) of soil is permitted. In early August, fine misting of the plant during morning hours is allowed. Under natural conditions, lithops withstands temperatures up to 50 °C (122 °F), but the optimal range during this period is 23-28 °C (73-82 °F).
During the flowering period from August to October (in nature, the rainy season with shortening daylight hours), lithops wakes up, begins intensive growth, pushes a peduncle out of the cleft between the leaves, blooms, and begins fruit maturation, which lasts several months. From mid-August, watering resumes and increases. The plant is watered generously but rarely, with mandatory complete drying out of the soil. Generous watering stimulates flowering in lithops older than 3 years. When flowering ends, watering is reduced for a smooth transition of the plant into the next period of the cycle. During this period, it is necessary to maintain a temperature no lower than 20 °C (68 °F).
During the renewal period from October to March (in nature, the dry season with short daylight hours), after flowering ends, lithops enters a state of slow growth, which many mistakenly call a second dormant period. The plant continues to develop slowly, yet this process is visually imperceptible; moreover, it may seem that the plant is dying, but this is a new pair of leaves beginning its vegetation, forming at the growth point of the old pair. New leaves grow inside the old ones, drawing out their nutrients. Over time, the old pair wrinkles, dries up, thins out, and ruptures, releasing the young leaves. At this time, the plant needs no watering or moistening, but requires good light and maintenance at a temperature of 10-15 °C (50-59 °F), no lower than 7 °C (45 °F). Watering ceases completely until early March.
During the growth period from March to June (in nature, the rainy season with increasing daylight hours), the new pair of succulent leaves that has taken the place of the old one begins active vegetation. The appearance and development of new leaves begins a new life cycle for the lithops, while the dying old leaves conclude the previous one. Watering is carefully resumed and gradually increased during March, brought to a maximum by mid-April, and reduced by the end of May. The plant increases in volume through moisture accumulation. From early spring, the optimal temperature is around 20 °C (68 °F).
Watering should be careful and moderate, with drying of the soil between waterings. Excess moisture can lead to rotting of the leaves and roots. Experienced growers water from the tray or by the immersion method, draining excess water after 10 minutes. For beginners, these methods are not recommended; it is better to use a fine spray bottle to moisten the soil and air, but it is very important that moisture penetrates deep into the container, since lithops has a long root. Water must not get into the cleft between the leaves, as this can provoke rot or sunburn. Filtered or settled water, soft and warm, is used. Lithops is indifferent to air humidity; spraying can be used for moistening during transitional stages between periods. The plant requires fresh air and regular room ventilation without drafts.
Lithops require bright sunny illumination throughout the year. Being under direct sunlight for 4-5 hours in the morning on a south, southeast, or east window, followed by partial shade in the afternoon, will be sufficient. As an alternative, 12-hour artificial lighting with fluorescent or LED lamps located at a distance of 10-15 cm (4-6 in) from the plant is acceptable. West and southwest windows are less acceptable, while north windows cannot be used at all, nor should plants be placed deep inside a room. In early spring, lithops growing on a south window should be shaded for 1-2 weeks to avoid sunburn. Plants deprived of light for 4-5 days become thin, stretch out, lose the brightness of their color, and may perish. With systematic lack of light during the summer period, the plant will not bloom. Changing its location is not recommended.
Lithops grow slowly and need repotting once every 3-5 years in spring or summer. Wide, light-colored containers 6-8 cm (2.4-3.1 in) deep are selected for planting, with a mandatory drainage layer of about 2 cm (0.8 in) at the bottom. In clay pots, adding drainage is not mandatory. The container size is chosen slightly larger than the size of the root system. They are planted in groups of 3-5 plants, since in solitary placement they develop much worse and rarely bloom. The top layer of soil is sprinkled with various decorative pebbles and gravel to prevent root collar rot.
The substrate must be stony, poor, loose, and possess neutral acidity. Due to a high peat content, using ready-made potting mixes for cacti is not recommended. A mixture of light sod soil with coarse sand or fine gravel in equal parts is used. A more complex mixture can also be used, consisting of 2 parts sod soil, 1 part leaf humus, 3 parts coarse river sand, and 2 parts crushed brick. The prepared substrate must be disinfected before planting.
Lithops are capable of obtaining all necessary nutrients from water and soil; consequently, feeding is not obligatory. But if the plant has not been repotted for more than 2-3 years, special fertilizers for cacti and succulents can be used at half strength during watering. Feeding can be done twice a year: in early May and in late August.
With proper care, lithops rarely suffer from diseases or pest attacks. In winter, plants can be damaged by fungus gnats, spider mites, and mealybugs. Various folk remedies exist for controlling these pests, but it is more effective to use ready-made insecticidal preparations according to instructions. Lithops get sick and perish most often from rotting of stems and roots due to an excess of moisture resulting from improper watering and poor drainage. In case of disease, watering must be significantly reduced and the plant treated with fungicides against fungi.