Golden Trumpet (Allamanda cathartica)

If you are looking for a plant that can brighten your home garden with vibrant yellow flowers, go for Allamanda cathartica, a species of flowering plant of the Apocynaceae family. Allamanda cathartica produces fragrant flowers of deep golden yellow. It is popularly known as the golden trumpet, or common allamanda, grown in tropical locations.

I. Appearance and Characteristics 

Allamanda cathartica, commonly called golden trumpet, common trumpetvine, and yellow allamanda, is a species of flowering plant of the genus Allamanda in the family Apocynaceae. It is native to Brazil. This plant is cited in Flora Brasiliensis by Carl Friedrich Philipp von Martius.

It does not twine, nor does it have tendrils or aerial roots. It can be pruned into a shrub form. If not pruned it can sprawl to a height of 20 feet.

The city of Canóvanas, Puerto Rico has adopted this species, known locally as canario amarillo, as its official flower.

The species is cultivated as a house plant. It requires a soil rich in organic matter, temperatures of not less than 18 °C (64 °F) during the growing season, plenty of moisture, and bright light but not direct sunlight. During the rest season from October to March, the plant should be watered more sparingly and can endure temperatures down to 13 °C (55 °F). It should be repotted every year until it is in a container of 40 to 50 centimeters (16 to 20 in). Propagation is by cuttings taken from April to May.

II. How to Grow and Care

Sunlight

Allamanda prefers strong light, including some direct sun. The plant can be adapted to full sun, or it can be grown successfully in an east-facing window with only a few hours of the morning sun.

Temperature and Humidity

Since allamanda likes warm, tropical temperatures, the most dangerous period for the plant is winter when even warm houses tend to become exceedingly dry. In these cases, it’s essential to mist your plant frequently to help it keep its leaves—dropping leaves is not a good sign or a sign of natural growth cycles.

Watering

Golden trumpet prefers well-drained soil and will rot if allowed to get wet feet. In general, you should let the top surface of the soil dry out before watering. Golden trumpet needs lots of water during the first year, in the growing and flowering season, and in times of high humidity.

Soil

A rich, peat-based potting soil with excellent drainage is beneficial for growing allamanda indoors.

Container and Size

Plant allamanda indoors in a large container that is at least 4 gallons. The pot must have many drainage holes. Choose an unglazed clay or terra-cotta pot so the container does not stay excessively moist. However, to increase the level of humidity in the air around the plant, place it on a pebble tray and water. Do not let the bottom of the pot become immersed in the water.

Fertilizing

Fertilization of golden trumpet is best with liquid water-soluble plant food. Young plants will benefit from extra phosphorus to encourage root development. Give the plant a break in winter and fertilize every 2-3 weeks in spring through summer. Avoid over fertilizing golden trumpet as this will result in fewer flowers due to overcrowding of foliage.

Pruning

Pruning the Allamanda plant is essential, which makes it easier to handle. The plant adjusts well to pruning and grows stronger. As it is a vigorous climbing vine, sometimes invasive, pruning helps set its boundaries for growth. Note that pruning the plant does not affect the flowering.  Pruning can be done several times in a year or once in two years. The ideal time for pruning is at the end of winter and before spring growth before blooming starts.

Propagation

The Allamanda plants can be propagated through seeds as well as stem-tip cuttings. Make sure the stem has three to four fully formed leaves at the tip.

How to plant seeds

You can plant the Allamanda seeds in a pot or in the ground in the garden area. Choose a pot with 7 inches of upper diameter and having drainage holes. Fill the container with well-drained soil.

Soak Allamanda seeds in water at room temperature for at least 24 hours. Using a file or sandpaper allows the seed’s shell to lightly break and allow water to seep into it.

Sow the seeds by making a hole in the soil of about one inch and cover it with soil. Apply water and maintain the moisture levels by checking if the topsoil becomes dry to touch. Seeds will begin to germinate in about a week.

Potting and Replanting 

Repot allamanda in the spring when new growth emerges—this is also a good time to take cuttings. When you repot, place the plant into a larger pot and provide a plant support ring, trellis, or other means of support if necessary. Allamanda can be grown as a low shrub, but it does best if allowed to grow up a simple support and trail slightly, which seems to show off its blooms to maximum effect.

Moving for the Summer

Potted indoor allamanda plants can be moved outside for the summer when it’s consistently warm. The pot needs to be gradually acclimated to the outdoors.

Place the indoor pot of allamanda in full sun or partial shade in the warm weather. It will need between 4 to 6 hours of direct sunlight daily but it can take even more sun than that. Continue to water, fertilize, and prune allamanda even when it is outdoors.

Move the plant back inside when the nighttime temperature gets down to 40 degrees Fahrenheit.

Pests and Diseases

Allamanda plant is resistant to most parasites and diseases. When the leaves begin to turn brown and curl, they are likely to be infested by aphids that may be colonizing the plant. Moreover, the vine is prone to attack red spider mites.

III. Uses and Benefits 

• Ornamental uses

Golden trumpet is a popular garden choice because its large, bright yellow trumpet flowers are produced in the wintertime, helping a garden have year-round appeal. It can be commonly spotted filling flower beds in tropical gardens, where its compact size helps it fit into small spaces. It is a good complement for Morning glories or Butterfly bush.

• Medicinal uses

Allamanda cathartica, a plant that grows in tropical and subtropical regions, is known to possess medicinal properties. The flower extracts have anti-inflammatory, antioxidant, antifungal, antibacterial, laxative, and in vitro hepatoprotective properties. The leaf extract has antioxidant and anti-inflammatory benefits, antifertility potency in males, and antimicrobial action against various drug-resistant clinical pathogens.