There’s one excellent reason to grow Allamanda indoors: their flowers. These plants, especially the Allamanda cathartica variety, feature large buttery yellow flowers with a brown throat and an exhilarating fragrance that hide among large, glossy leaves. When the plant is in full bloom, it’s likely to be covered with these four-inch flowers and will be the pride of your collection. The most dangerous period for Allamanda cultivation 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.
Light
Allamanda prefers strong light, including some direct sun. They can be adapted to full sun, or they can be grown successfully in an east-facing window with only a few hours of the morning sun. Adequate sunlight is essential for blooming.
Soil
A rich, peat-based potting soil with excellent drainage is beneficial.
Water
Water liberally throughout the summer, making sure your growing pot has good drainage. It’s also helpful to mist every other day or so to provide adequate humidity. In the winter months, reduce watering, but don’t let the plant dry out and make an effort to keep the root ball warm.
Fertilizer
Feed with a weak liquid fertilizer throughout the growing season. Cut fertilizer back to once a month or so in the winter.
Allamanda Varieties
There are more than a dozen species of allamanda, but the most common one in cultivation is the Allamanda cathartica. This plant is sometimes called the golden trumpet and is a common landscape plant in subtropical and tropical regions. These are a few popular varieties within this species:
‘Grandiflora’ is certainly grand, with stunning large yellow flowers.‘Hendersonii’ features redbuds and golden-colored flowers.‘Flore Pleno’ is a lovely showy plant with double white flowers.‘Williamsii’ boasts eye-catching trumpet-like double yellow flowers that bloom year-round but has a poisonous milky sap.
Propagating Allamanda
Allamanda roots readily from stem tip cuttings. To have the best chance of success, take the cutting early in the growing season from a fresh green shoot. Use a rooting hormone for the best chances of success and pot the cutting into a fresh pot of seed-starting soil. Place the cutting in a warm, humid environment with bottom heating and wait for new growth to emerge before potting out into a larger container.
Repotting
Repot Allamanda in the spring when new growth emerges—this is also a good time to take cuttings. When you repot, place it into a larger pot and provide some 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. This seems to show off its blooms to maximum effect.
Common Pests & Diseases
Allamanda is somewhat vulnerable to pests, especially aphids and mealybugs. Keep your eyes peeled for signs of infestation, such as damaged leaves, and treat at the first indication. Treat with insecticidal soap every week or so until the insects are no longer there.
