Hoyas, also called wax plants or wax flowers, are tropical plants that are actually flowering vines. While they can grow outdoors in USDA plant hardiness zones 10B to 11, they can be grown indoors in all other climates. Hoya plants are slow growing and can thrive for more than 20 years when properly cared for. However, sometimes even the most thriving hoyas can become unhealthy. Before you throw out what you may think is a dying hoya, take steps to try to rejuvenate it.
Keep the plant undisturbed---except for watering--when it is budding. Do not move, prune, re-pot or do anything else to it while it is busy budding.
Move the plant to a spot that receives about four hours of direct sunlight each day.
Water your hoyas properly. In the winter, allow the soil to completely dry out between waterings, then only water enough to wet the top inch of soil. In the spring and summer, water more thoroughly--soaking the soil slowly until it comes out the drainage holes, and watering it again when the soil is dry for the first couple of inches (check with your finger). In the fall, start to slow down the waterings to prepare it for winter.
Mist the hoyas with water about three times a week, but not when they are budding or blooming. Mist especially during the winter when the air tends to be dry.
Keep the flowers on a hoya plant, even once they are dead. Unlike most plants, hoyas do not benefit from deadheading.
Fertilize your hoyas with a balanced fertilizer that is labeled 15-15-15. Do this every three weeks and only when the plant is actively growing, usually during the spring and summer months.
Treat the hoya for insects, if necessary. Spider mites are a likely culprit. Take a sample damaged leaf to your local nursery or county extension office to have them identify the insect that is doing the damage. Then, apply an appropriate insecticide and follow the directions on the label for application methods and frequency.
Move the hoya plant to a location that is above 59 degrees F and above, even at night. Hoyas prefer temperatures between 64 and 68 degrees F. However, during the winter months, keep them in an area that is between 50 to 55 degrees if possible.
Re-pot your hoya. If it looks like it has outgrown its container, it may be pot bound. Use fresh high quality potting soil and plant it to the same depth it was previously planted, but in the next size container.
Prune back your hoya if all else fails. Cut off the damaged or diseased leaves and continue to provide proper care for your hoya.