Origin and Common Names
Bidens macrantha (Sch.Bip.) Cufod. is a flowering plant species that belongs to the family Asteraceae. It is native to the Americas, particularly in the regions of Mexico, Central America, and Colombia. The plant is commonly known as "giant beggarticks", "greater bur-marigold", "large-flower beggar-tick", and "Spanish needles".
General Appearance
Bidens macrantha is a tall and robust herbaceous perennial plant that can grow up to 6 feet (1.8 meters) tall. The stem is deeply grooved and colored green or reddish-brown. The leaves are opposite, pinnately compound with 5 to 11 leaflets, and serrated margins.
The flowers of Bidens macrantha are daisy-like with yellow rays that can reach up to 2 inches (5 centimeters) long. The flowerheads are solitary or arranged in clusters at the top of the stem or in the leaf axils. The plant blooms from June to September.
The fruit of Bidens macrantha is an achene with two spreading barbed bristles that can adhere easily to clothing or animal fur.
Uses
Bidens macrantha has several traditional medicinal uses. The leaves and flowers of the plant are used to treat skin diseases, wounds, and gastrointestinal problems. The plant is also used as a diuretic, emetic, and purgative.
Furthermore, Bidens macrantha is an important ornamental plant. It is commonly grown in gardens and landscapes for its attractive flowers and foliage. The plant is also used for erosion control and wetland restoration due to its ability to grow in moist environments.
In addition, the seeds of Bidens macrantha are a valuable source of food for several bird species such as mourning doves, quails, and sparrows. The plant is also an important host plant for various butterflies and moths.
Light Requirements
Bidens macrantha needs full sunlight exposure to grow properly. It grows best in open areas, where it receives ample sunlight throughout the day. It can also tolerate partial shade but grows sparsely and produces fewer flowers in such conditions.
Temperature Requirements
The ideal temperature range for Bidens macrantha growth is between 20°C and 28°C. It grows well under warm conditions and tends to wilt under hot and dry weather. Therefore, it requires plenty of water to keep the soil moist during such weather conditions.
Soil Requirements
Bidens macrantha grows in well-drained soils that are fertile, rich in organic matter, and have a pH range of 5.5 to 6.5. The soil should not be too heavy, nor too compacted. It grows naturally in wetland soils, but it can adapt to various soil types and conditions. This plant is highly sensitive to water-logging and requires proper drainage to avoid root rotting.
Cultivation Methods
Bidens macrantha is a hardy plant that is easy to grow and care for. It is adaptable to a wide variety of growing conditions from full sun to partial shade in well-drained soils. This plant can be propagated from seeds or cuttings, and it is best to start the propagation process in the spring or early summer.
Watering Needs
Bidens macrantha requires regular watering, especially during the growing season when the soil should remain moist but not waterlogged. Ensure that the plant receives sufficient water every week, especially during hot, dry summers. Reduce watering in the fall and winter, as the plant requires less moisture during the dormant season.
Fertilization
Bidens macrantha benefits from regular fertilization during the growing season. Apply a balanced fertilizer once every 4-6 weeks to promote healthy growth and blooming. For best results, use a slow-release granular fertilizer sprinkled around the base of the plant.
Pruning
Bidens macrantha should be pruned in the early spring or fall to promote bushy, compact growth. Trim back any dead, diseased, or damaged branches to maintain the plant's health and appearance. Pinch back the growing tips of the plant periodically to encourage branching and a more abundant display of flowers.
Propagation of Bidens macrantha
Bidens macrantha can be propagated via seeds, stem cuttings, or division of mature plants.
Propagation by seeds
Seeds can be collected from mature Bidens macrantha plants and sown directly in well-draining soil in a warm, sunny location. Seeds should be covered lightly with soil and kept moist until germination occurs. Germination typically occurs within 2-3 weeks, and seedlings can be transplanted to their permanent location once they have grown their first true leaves.
Propagation by stem cuttings
Bidens macrantha can also be propagated by stem cuttings taken from healthy, mature plants. Cuttings should be taken during the growing season and should be about 4-6 inches in length. Remove the bottom leaves of the cutting and dip the cut end in rooting hormone. Plant the cutting in well-draining soil and keep it moist until roots develop. Once roots have developed, the cutting can be transplanted to its permanent location.
Propagation by division
Mature Bidens macrantha plants can be divided in the spring or fall. Using a clean, sharp shovel, dig up the plant and gently separate the root ball into smaller sections. Each section should have at least one shoot and a portion of the root system. Replant the sections in well-draining soil and water thoroughly. The new divisions will establish quickly if kept moist and protected from direct sunlight until new growth begins to appear.
Disease Management
Bidens macrantha is susceptible to several diseases that can cause significant damage to the plant health. Some common diseases and ways to manage them include:
Downy Mildew
Downy mildew is a fungal disease that causes yellow spotting on the leaves, wilting, and stunted growth in Bidens macrantha plants. To manage downy mildew, remove infected leaves and spray with fungicide to prevent further spreading.
Root Rot
Root rot is caused by soil-dwelling fungi that attack the plant roots, causing them to rot. This can lead to stunted growth, wilting, and death of the plant. To prevent root rot, avoid overwatering and ensure proper drainage. If the plant is already affected, remove the infected plant and treat the soil with fungicide.
Bacterial Spots
Bacterial spots are caused by Xanthomonas campestris bacteria, leading to the yellowing of leaves and dark spots on the foliage. This disease can cause the plant to become stunted, and in severe cases, death. To manage bacterial spots, remove the infected plant parts and treat the plant with copper-based fungicides.
Pest Management
Bidens macrantha is also prone to attack by various pests, which can affect the plant health and reduce yields. Some common pests and ways to manage them include:
Aphids
Aphids are small, pear-shaped insects that can suck sap from the plant, causing stunted growth, yellowing, and wilted leaves. To control aphids, spray the plant with insecticidal soap or neem oil.
Spider Mites
Spider mites are tiny mites that suck plant sap, causing yellowing of leaves and webbing on the plant. Manage spider mites by increasing humidity levels and spraying the plant with insecticidal soap or neem oil.
Caterpillars
Caterpillars are the larvae of moths and butterflies that feed on the foliage, causing leaves to become skeletonized. To control caterpillar infestations, remove the larvae by hand and use biological insecticides.
By following these pest and disease management techniques, Bidens macrantha plants can remain healthy and produce high yields.
