There are between 200 and 300 species of Hoya plant, according to the University of Illinois. Of these, Hoya carnosa, with its light-pink flowers, is the most commonly grown as a houseplant. Hoyas are evergreen vines or shrubs that are known for their slow growth and ease of care. They have the same basic care needs regardless of the species. Hoyas are often grown in containers and can be cultivated indoors or outdoors, if the conditions are right.
Hoya plants are native to the tropical forests of Polynesia, Australia and Asia, according to the University of Illinois. Ideally, they need warm, humid conditions in order to thrive. Due to their need for warm temperatures, Hoyas are often grown as indoor plants. Outdoors, they thrive in tropical and subtropical climates. In the United States, they can grow outdoors in U.S. Department of Agriculture (USDA) growing zones 10 through 12.
Soil nemotodes are a problem with Hoyas, according to the University of Florida. These microscopic roundworms are not visible to the naked eye. There are many species of nemotodes, some of which are beneficial to plants. Others are parasitic. These parasitic nemotodes will attack, consume and destroy the roots of hoya plants if present in the soil. Because of this, the ideal condition for soil is to use commercial potting soil that has thoroughly been sterilized, rather than soil that is taken from the garden. Hoyas will grow in various soils, including clay, sandy and loamy soil.
Hoyas are known in part for their ability to grow in low-light conditions, according to the University of Illinois, but they will grow more quickly and bloom more readily if they are exposed to at least some sunlight each day. Bright but indirect or filtered sunlight is best.
Correct watering practices must be followed for the Hoya plant to grow well. The ideal condition for watering is to let the soil dry all the way out before watering again. The drying of the soil will happen more quickly in the spring and summer than in the fall and winter, which is when the plant enters dormancy.
Hoyas enjoy humid conditions. While they can grow in dry air, they benefit from frequent misting, according to North Dakota State University (save when the flowers are blooming). Or, place your Hoya on a humidity tray--a shallow basin filled with pebbles and water.