Angel trumpets are considered shrubs or small trees and are native to Brazil. They are hardy in climates rated between USDA zones 10 and 12, with some varieties rated to zone 9. In these warm zones, the plants bloom large, trumpet-shaped flowers all year long. Most of Southern California, with the exception of the mountains, are in zones 9 to 11, so if have angel trumpets adorning your garden, there are several things you can do not just to keep your plants healthy, but to encourage more blooms.
Keep your angel trumpets well watered. The soil should be moist at all times. During the summer months in Southern California, when temperatures are extremely hot, you may need to water them every day.
Fertilize your potted angel trumpets every two to three weeks with a balanced fertilizer, such as one labeled 17-17-17. For angel trumpets planted outdoors, use a fertilizer labeled 15-5-10. Follow label instructions for proper dosing and application. Fertilizers come in different strengths and in both liquid and granular forms.
Fertilize twice a year with a fertilizer high in nitrogen and labeled 34-0-0. Mix 3 tablespoons of fertilizer in 2 gallons of water. Apply in early spring and then again in late summer.
Move potted angel trumpets into the shade during the hottest part of the day during the summer months. Do this if you notice your plant is losing leaves or if it is not blooming as normal.
Prune your angel trumpets before the first frost if you live in a climate cooler than USDA zone 9. Cut it back to about 6 inches above the ground and water it with a gallon of water. Apply 3 or 4 inches of mulch, such as wood chips or straw, to protect the roots from freezing. If your plant is potted, move the whole plant to a sunny area of your home, such as a south-facing window. Or cut it back as you would an outdoor plant and move it indoors to a cool area of your home, such as a basement or attached garage.