Overview:
Calendula amplexicaulis Thunb. is a species of the calendula family (Asteraceae), native to East Asia and commonly called the Asian calendula. It is an annual herbaceous plant that is easily recognized by its bright yellow or orange-yellow flowers, which bloom in large quantities from late spring to early summer.
Common Names:
The plant has several common names, including Asian marigold, copper marigold, Egiku, and Tsumagiku, among others.
Appearance:
Calendula amplexicaulis Thunb. grows up to a height of 60-80 cm and has a branched stem. The leaves are dark green, slightly succulent, and clasp the stem without a petiole. The flowers are large and can reach up to 6 cm in diameter. They have a central dark disc surrounded by a ring of flat ray florets, which are typically yellow or orange-yellow in color. The plant blooms from May to June.
Uses:
The plant has several medicinal uses in traditional Chinese medicine. The flowers are believed to have anti-inflammatory and antimicrobial properties and are used to treat skin conditions, digestive problems, and menstrual irregularities. Calendula amplexicaulis Thunb. is also used as an ornamental plant in gardens and for cut flowers.
Light Requirements:
Calendula amplexicaulis Thunb. requires full sun or partial shade to thrive. It can grow under direct sunlight, but if planted in a very hot area, it must be given partial shade to prevent the flowers from wilting.
Temperature Requirements:
This plant is native to Asia and can withstand both high and low temperatures. The ideal temperature range for growing calendula amplexicaulis Thunb. is between 10°C and 30°C. However, it can still survive below 0°C with proper care.
Soil Requirements:
Calendula amplexicaulis Thunb. thrives in well-draining and fertile soil. The pH level should be between 6.0 and 7.0. It can tolerate several soil types, such as sandy loam, loamy sand, and clay loam. Ensure that the soil is not compacted, as this will prevent proper growth of the plant.
Cultivation methods
The plant Calendula amplexicaulis Thunb. is a hardy plant that grows best in USDA hardiness zones 4-8. It prefers well-drained soil that is rich in organic matter and full sun to partial shade. The plant can tolerate mild frost and drought conditions. The plant can be propagated by both seeds and cuttings.
Starting calends amplexicaulis from seed indoors 6-8 weeks before the last frost can give it a head start in development. Sow the seeds in seed-starting mix in pots or trays, and water the soil lightly. Cover the containers with clear plastic to hold moisture and keep the soil warm until seedlings appear.
Watering needs
Calendula amplexicaulis Thunb. prefers moist soil that is not too wet. The soil should be damp to the touch but not waterlogged; avoid overwatering. Water the plant deeply once or twice a week, depending on the soil drainage and weather conditions. Allow the soil to dry out slightly between watering. Overwatering can lead to root rot and damage to the plant’s health.
Fertilization
The plant Calendula amplexicaulis Thunb. does well in soil that is enriched with organic matter. Adding well-rotted compost or aged manure to the soil before planting will provide the necessary nutrients for good growth. Top dressing with organic matter in the form of compost or manure every three to four months will help boost plant health. Avoid using synthetic fertilizers, which can lead to the accumulation of salts in the soil and harm beneficial soil organisms.
Pruning
Pruning can be beneficial for the growth and appearance of the plant Calendula amplexicaulis Thunb. However, it is not necessary. Pruning lightly once or twice a year can help control the size of the plant and promote bushier growth. Deadheading the plant, which is the removal of spent flowers, can also promote the growth of new blooms. Cut off the spent blooms where the stem meets the foliage.
Propagation of Calendula amplexicaulis Thunb.
Calendula amplexicaulis Thunb., also known as the Sticky Calendula, can be propagated by both seeds and stem cuttings.
Propagating through seeds
The most common method of propagating Calendula amplexicaulis Thunb. is through seeds. Seeds should be sown in well-draining soil and lightly covered with a thin layer of soil. They should be kept moist to encourage germination, which usually occurs within 10 to 21 days.
Seedlings should be thinned to about 6 to 8 inches apart once they are large enough to handle. This will ensure that they have enough space to grow.
Propagating through stem cuttings
Calendula amplexicaulis Thunb. can also be propagated through stem cuttings. This method is particularly useful if you want to create new plants that are identical to the parent plant.
Stem cuttings should be taken from healthy plants during the growing season. The cuttings should be about 4 to 6 inches long and should have at least two nodes. They should be taken from the lower part of the plant.
The bottom leaves should be removed, and the cuttings should be dipped in rooting hormone. They should then be planted in well-draining soil and kept moist. The cuttings should root within 2 to 4 weeks, and can then be transplanted into their permanent location.
Disease and Pest Management for Calendula amplexicaulis Thunb.
Calendula amplexicaulis Thunb. commonly known as the calendula plant is a species of marigold grown for its vibrant orange or yellow blooms. The plant is relatively easy to grow and care for, but it is susceptible to various pests and diseases.
Common Diseases of Calendula amplexicaulis Thunb.
Various fungal diseases affect calendula plants. Gray mold (Botrytis cinera) is a common fungal disease that affects calendula. It thrives on humid conditions, and it appears as a grayish mold on the leaves, petals, or shoots of the plant. Powdery mildew (Erysiphe cichoracearum) is another fungal disease that causes a white powdery growth on the leaves of the plant.
Fusarium wilt is a disease caused by the fungus Fusarium oxysporum. The disease causes the leaves of the plant to wilt and turn yellow, and it eventually kills the plant.
Root rot is caused by overwatering the plant. Over-watering creates a perfect breeding ground for fungi like Rhizoctonia solani, which causes root rot. This disease is characterized by the plant’s yellow leaves, and the plant dies if the disease is not managed.
Pest Control
Calendula plants are prone to the attack of several pests, including aphids, spider mites, and whiteflies.
Aphids are small insects that suck the plant's sap. They appear in large numbers, and the damage they cause affects the plant's growth and the vigor of flowers. Neem oil spray, insecticidal soap or horticultural oil are effective ways to manage aphids.
Spider mites are bugs that look like tiny spiders and are hard to see with the naked eye. They feed on the plant and suck out the sap, leading to the plant's wilting and yellowing. Spraying the plant with neem oil or insecticidal soap will control spider mites.
Whiteflies are tiny, winged pests that feed on the plant's underside and can cause the leaves to yellow, wilt, and fall off. Yellow sticky traps are an effective way of capturing them.
Disease Control
To control fungal diseases like gray mold and powdery mildew, it is essential to practice proper sanitation. Remove and destroy any infected plant parts and avoid overhead watering. Applying a fungicide spray is a practical way to manage fungal diseases.
Fusarium wilt and root rot diseases are challenging to manage, and infected plants should be removed and destroyed. Ensure that only healthy plants are planted to prevent the spread of the disease.
In conclusion, good cultural practices like proper watering and sanitation can help prevent pests and diseases in Calendula amplexicaulis Thunb. Infection can be managed by applying fungicides or the use of effective pest control methods.
