A Detailed Guide to Geranium Cultivation Methods and Key Technical Points

Geranium is also called "foreign hydrangea" and "balahong." Its flowering period is quite long, from October of the current year to June of the following year, with the peak bloom period being April to May. Flower colors include red, peach red, magenta, flesh red, white, and others. Other cultivated species include large-flowered geranium, shield-leaved geranium, scented geranium, musk geranium, horse-shoe geranium, and others.

Geranium is a perennial herbaceous plant, originally growing in the Cape of Good Hope area of South Africa. Because it is drought-tolerant, light-loving, not particular about soil, highly adaptable to the environment, and relatively easy to cultivate, although it was introduced to China only about a hundred years ago, it is very widely cultivated. It can grow almost everywhere from Northeast China in the north to Guangdong in the south. It enters the flowering stage relatively early; when propagated from seed abroad, it can bloom in only four months; its flowering period is especially long.

Geranium prefers an ecological environment that is warm in winter and cool in summer, warm and dry, with ample sunlight. When the summer temperature exceeds 24°C, it is unfavorable for its growth, and the plant will enter a semi-dormant state; when the winter temperature drops below 10°C, its growth vigor noticeably weakens, and when it drops below 3°C, the plant basically stops flowering and growing. If placed in a low-temperature environment below 0°C for a long time, it may suffer cold damage.

I. Geranium Cutting Propagation

Geranium is best propagated by cuttings. Except for July to August, when the plant is in its dormant period and the hot weather makes cuttings prone to rot, making propagation unsuitable, cuttings can be taken at other times. In particular, cuttings taken in a greenhouse pot or box in January to February have the best survival rate, and plants cultivated from them can bloom by winter of the same year. For open-field or cold-frame cuttings, the most suitable times are the two spring and autumn seasons of September to October or April to May.

Cuttings should be selected from one-year-old branch tips with terminal buds, about 10 cm in length. Remove 2 to 3 basal leaves, place in a cool, shaded area for several hours until the wound dries, then insert into a pot or box filled with clean sandy soil. Then place in a semi-shaded area, pay attention to ventilation, maintain appropriate humidity, and do not water too much, otherwise the cuttings are prone to rot. Under greenhouse conditions of 15°C to 20°C, they will root in about 15 days.

According to experience, when the axillary buds growing in the leaf axils reach 8 to 9 cm in length, break them off by hand to use as cuttings; because their wounds are small and easy to heal, the survival rate is high. Healthy cuttings come from healthy mother plants. For the mother plants selected for cuttings, watering should be appropriately controlled, sufficient light should be given, and ventilation should be strengthened to promote sturdy branches.

II. Pot Cultivation of Geranium

Geranium is mostly grown in pots. For pot cultivation, the growing medium is made by mixing 3 parts sandy loam, 1 part leaf mold, and 1 part river sand; it is best to add a small amount of superphosphate as a base fertilizer. When the seedlings are about 10 cm tall, pinch off the growing tips to encourage branching. After the flowers fade, cut off the flower stems to encourage continuous new leaf growth and new flowers from the leaf axils. Do not water too much; keeping it moist is sufficient. On rainy days, promptly pour out accumulated water in the pot; excessive moisture will cause yellow leaves, leaf drop, and leggy growth. Apply once every 20 days a human and livestock manure urine solution diluted with 5 times water; topdressing with phosphate fertilizer will make it bloom even more profusely. In winter, move it indoors or to a shaded shed to overwinter. Repotting is done in March, with appropriate pruning to remove some old and weak branches, and replacing with freshly prepared growing medium.

III. Pruning and Shaping

Geranium grows rapidly and needs pruning and shaping every year. If not pruned, the branches and leaves become messy and crowded, the plant shape becomes unsightly, the flowers bloom smaller and smaller, and the ornamental value decreases. When the seedlings grow to 12 to 15 cm tall, pinch off the growing tips to encourage branching. After the flowering season (mostly after the Beginning of Autumn), cut off overly dense, weak, pest- or disease-affected branches, and leggy branches from the base all at once, leaving 3 to 5 evenly distributed main branches, then shorten the main branches and side branches, leaving only 3 side buds on each side branch, so that the branches of the entire plant are evenly and compactly distributed, and the plant shape is full and stocky. After pinching, topdressing should be applied promptly to promote sturdy new branch growth, but do not water heavily in the short term to prevent root rot.