How to grow Clerodendrum thomsoniae? The latest cultivation methods and precautions

Clerodendrum thomsoniae is a climbing shrub of the genus Clerodendrum in the family Verbenaceae, and a beautiful ornamental plant. Generally, when grown in pots, it is kept very short due to pruning restrictions. It is often used for greenhouse cultivation and ornamental display, can be trained on a flower trellis, and is also grown in pots to accent windowsills and small summer courtyards, as well as for parks or tourist sites to build flower baskets, arches, arbors, and so on. Now let us take a look at the cultivation methods and precautions for Clerodendrum thomsoniae!

Growth habits of Clerodendrum thomsoniae

Clerodendrum thomsoniae prefers a warm, humid, semi-shaded environment with plenty of sunlight. It is not cold-tolerant, and the winter temperature should not be lower than 8°C. Below 5°C, the stems and leaves are prone to frost damage; in mild cases this causes leaf drop, and in severe cases the tender stems wither. During the vegetative growth period, the temperature can be relatively high; even above 30°C, as long as water is supplied adequately, it can still grow normally. During reproductive growth, that is, the flowering period, the temperature should be relatively lower, around 17°C.

Propagation methods of Clerodendrum thomsoniae

1. Cuttings: Clerodendrum thomsoniae cuttings are generally taken from May to June each year. You can choose the tender top shoots of healthy, disease-free branches, or cut the lower old branches into 8-10 cm stem sections as cuttings. The cutting bed can use substrates such as peat, perlite, leaf mold, river sand, and vermiculite. The optimum temperature for rooting is 21°C, and a cutting bed temperature of 26°C is very favorable for rooting. Roots can form 3 weeks after cuttings are inserted. If the base of the cuttings is treated with a 0.5-0.8% indolebutyric acid solution for 1-2 seconds, rooting will be faster and more abundant.

2. Sowing: The seeds of Clerodendrum thomsoniae have a short lifespan and should be sown immediately after collection. Sowing can be done from March to April each year by broadcasting in a shallow pot, keeping the temperature at 24°C. Seedlings can emerge in 10 days. When the seedlings are 10 cm tall, repot and transplant them, and they can bloom in the second year. However, the sowing method is not easy to succeed with, so the cutting method is recommended for propagation.

Cultivation methods for Clerodendrum thomsoniae

1. Soil: For growing Clerodendrum thomsoniae, use fertile, loose, and well-drained sandy loam. For pot cultivation, use a mixture of culture soil or peat soil and coarse sand. A commonly used soil formula is 4 parts leaf mold, 4 parts garden soil, and 2 parts sand.

2. Watering: Clerodendrum thomsoniae is relatively sensitive to moisture and needs sufficient water during the growing period. During the stem and leaf growth period, keep the soil moist, but do not overwater. Too much water causes only vines to grow without flowering, and may even cause leaves to yellow and drop and roots to rot and die. If the branches wither, stop watering and let it recover and sprout new leaves. In the hot summer season, water thoroughly and provide appropriate shade. In winter, reduce watering to let it go dormant so it can overwinter safely.

3. Light: In winter, Clerodendrum thomsoniae needs sufficient light. When the summer weather is too hot, it should be shaded, otherwise the leaves turn yellow. When light is insufficient, it causes vine-like growth and no flowering. Flower bud differentiation is not affected by photoperiod, but stronger light promotes flower bud differentiation and development. It should not be placed in darkness for too long; at temperatures above 21°C, exceeding 24 hours will cause flowers to drop.

4. Fertilizing: Clerodendrum thomsoniae should not be fertilized too much. Fertilize once every half month. During the flowering season, apply 1-2 additional applications of phosphorus-potassium fertilizer, “Huiyou” 20-8-20 high-potassium nitrate fertilizer for all seasons, or apply diluted, fully decomposed cake fertilizer water once every 7-10 days. Applying fertilizer 3-4 times in a row is sufficient. In winter, reduce watering and stop fertilizing. If yellowing is observed during cultivation of Clerodendrum thomsoniae, apply 0.2% ferrous sulfate water together with topdressing, and the leaves will gradually turn from yellow to green.

5. Pruning: For Clerodendrum thomsoniae, when potted cuttings or seedlings grow to 15 cm, cut the branches 10 cm above the pot rim to promote the sprouting of strong new branches. During the growing period, strictly control the height of the branches and pay attention to topping and pinching to achieve neat branching and dense flowering in the future. Half a month after pinching, apply daminozide or chlormequat to control plant height, achieving a short plant, lush leaves, and abundant flowers.

6. Repotting: Potted Clerodendrum thomsoniae commonly uses 12-15 cm pots, with 3 plants per pot. Generally, repot once every 1-2 years, either in early spring or after the flowers fade. When repotting, first cover the drainage hole with broken tile pieces, then add a small amount of bone meal as base fertilizer, then fill with new culture soil and plant the plant, leaving 2-3 cm of rim space for fertilizing and watering. After repotting, water thoroughly and place in a shady spot to recover. After recovery, move it to a sunny place for care.

Precautions for growing Clerodendrum thomsoniae

1. During cultivation, Clerodendrum thomsoniae can develop leaf spot disease. At first there are just small brown spots, but if not treated promptly, large black spots will appear and the leaves will wither and die. Therefore, once disease is found, immediately spray the leaves with an 800-fold dilution of chlorothalonil, once every 7-8 days, for 2-3 consecutive times, and it can basically recover.

2. The main pests of Clerodendrum thomsoniae include scale insects and whiteflies, which can be sprayed with a 1000-fold to 1500-fold dilution of 40% omethoate. For leaves that cannot spread normally and become chlorotic and yellow due to alkaline soil, irrigate with a 0.2% ferrous sulfate solution. For mosaic disease and fungal diseases, promptly remove fallen diseased leaves, strengthen ventilation, and keep the leaves dry to control the condition.