Hoya is an Asian native plant introduced by Scottish botanist Robert Brown and named in honor of the 18th-century botanist Thomas Hoy. Gardeners today find it a fragrant, low-maintenance tropical flower. They are slow to moderate growers, and should be planted outside in spring or early summer.
Flowering plants in the genus Hoya are part of the Asclepiadaceae family, otherwise known as the milkweed family. Newer taxonomy places the genus in the Apocynaceae (dogbane) family. Although hoya isn't difficult to pronounce, you may prefer to call the plants by one of their other common names, including the wax plant, wax flower, Indian rope plant, porcelain flower, or honey plant.
|Botanical Name||Hoya carnosa|
|Common Name||Hoya, wax plant, wax flower, Indian rope plant, porcelain flower, honey plant|
|Plant Type||Tropical succulent|
|Mature Size||12-20 ft.|
|Sun Exposure||Bright, natural light|
|Bloom Time||Spring or summer (but some varieties bloom in fall)|
|Flower Color||Yellow, orange, pink, burgundy, white, near black|
|Hardiness Zones||8-11 (USDA)|
|Native Area||Tropical Asia, Australia|
|Toxicity||Non-toxic to humans and pets|
Hoya flowers grow in a ball-shaped cluster, similar to mophead hydrangeas. Each cluster may contain up to 40 individual flowers, packed tightly together. The individual flowers are perfect looking. They appear to be molded from wax or porcelain, thus the common names. Flowers often sport a colored eye in the center of the corona.
The plants produce woody stems with waxy leaves, which remain evergreen. You can train a hoya plant as a vine, or allow it to trail over the side of the container. Either way, expect the full length or height of the plant to be 2-4 feet.
Place your hoya plant in a hanging basket where you can admire it from your favorite seat on the deck or porch. Hoya plants will cling to a small trellis, providing a vertical accent in your tropical container garden. A hoya plant would appreciate the humid conditions alongside any pond, fountain, or other water feature in your landscape.
According to The University of Kansas Health System, hoya's leaves and sap are non-toxic to humans and pets. Still, if your child or pet eats them, it's best to call your doctor or veterinarian for advice.
Hoyas thrive best when they get bright, non-direct sunlight.
A well-draining, lightweight soil mix is what hoyas should be planted in. Too much moisture and the roots will rot.
Hoyas should be watered weekly, and left to let dry completely between waterings.
Temperature and Humidity
As a tropical plant, hoyas thrive in warm and moist, humid climates.
Hoyas should be fertilized monthly; The International Hoya Association suggests feeding them with a fertilizer that includes nitrogen, phosphorus, and potassium.
- H. Archboldiana: Cup-shaped creamy flowers with a maroon corona
- H. Compacta 'Indian Rope': Pale pink flowers and curly leaves; pretty even when the plant isn’t blooming
- H. Cumingiata: Yellow flowers with red corona; fragrant
- H. Kerrii Variegata 'Sweetheart Plant': Heart-shaped foliage with white margins; yellow and orange flowers
- H. Onychoides: Purple flowers with an exaggerated star shape
When your hoya plant finishes blooming, leave the flower stalk, as it may produce new flowers. Removing the stalk forces the plant to produce a new stalk, which delays blooming and wastes the plant’s energy. Hoyas are light feeders, and a monthly drink of compost tea or dilute fish emulsion provides all the nutrition these tropicals need.
Hoya plants don’t ask for much, beyond the well-draining soil and the warm, humid conditions that many tropical flowers crave. You can grow the hoya if you live in USDA growing zones 10-12; elsewhere you must grow it as a tropical container plant or greenhouse specimen.
Choose a location with full to partial sun. Plants that receive less than a half-day of sunlight may not produce flowers.
Potting and Repotting Hoya
Hoyas like the security of a snug pot and plants that are a bit root-bound will flower more prolifically than those that are swimming around in a giant pot. Hoyas don’t like wet feet or heavy soil, and as many grow as epiphytes in nature (similar to bromeliads and orchids). Mixing your regular potting soil with orchid potting mix in a 1-1 ratio will provide an ideal growing medium for your hoya plant.
Also, when repotting, use pasteurized soil or growing medium in either new pots or those that have been washed in a solution of chlorine bleach and water.
Hoyas will bloom throughout the summer months, and you should bring them indoors when temperatures drop below 50 degrees Fahrenheit.
Common Pests and Diseases
Hoyas are vulnerable to sap-sucking pests like aphids, mealybugs, and spider mites. All can be controlled with neem oil. Once you've treated the plant, wipe away pest residue with a clean, soft cloth.
Fungal infections are also common diseases for the hoya. Botrytis blight can cause rot and kill your plant; it shows up as greyish patches. Treat with fungicide, and repot in sterilized potting medium.