Hoya Plants, The Wax Flower

Wax plant (Hoya carnosa)
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Although we can thank the Scottish botanist Robert Brown for introducing the Asian native Hoya into cultivation, the plant genus is named in honor of the 18th century botanist Thomas Hoy. If he were alive today, Mr. Hoy might strive to introduce more gardeners to this fragrant, low maintenance tropical flower.

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.

Hoya Identification

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” and bear scrutiny: 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 between two and four feet. 

Planting Hoya Flowers

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 sun may not produce flowers. 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. Hoyas will bloom throughout the summer months, and you should bring them indoors when temperatures drop below 50 degrees F.

Hoya Flower Care

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. 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.

Design Tips With Hoya Plants

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.

Hoya Varieties to Try

  • H. Archboldiana: Cup shaped creamy flowers with a maroon corona
  • H. Carnosa: Most common in the trade, an easy hoya for beginners; pale pink flowers with a magenta corona
  • H. Compacta ‘Indian Rope’: Pale pink flowers, curly leaves offer interest when plant isn’t blooming
  • H. Cumingiata: Yellow flowers with red corona; very fragrant
  • H. Kerrii Variegata: Heart-shaped foliage with white margins; yellow and orange flowers
  • H. Onychoides: Purple flowers have an exaggerated star shape