Jackie Bantle
Saskatchewan Perennial Society
Winter is a good time for gardeners to focus more on their houseplants and perhaps even purchase a few new ones in celebration of a new year. One of my favorite house plants over the last couple of years has been a hoya plant (Hoya carnosa). Not only have I found this plant to be easy to grow but when it blooms, the flowers are beautiful.
Hoya refers to a genus of plants in the dogbane family (Apocynaceae) that has over 500 different species. Hoya plants are native to Southeast Asia, Japan and Taiwan. Often referred to as ‘Porcelain flower’ or ‘wax plant’, hoya plants are either epiphytic (growing on the surface of another plant or plant-like substance) or lithophytic (growing on the surface of a rock) vines. In nature, hoya roots are rarely found in the soil, they derive their nutrients from the air and rain. Despite their natural growth habit, indoor hoya plants are usually grown in containers with the roots buried in porous media. The leaves of hoya plants are fleshy and leathery. The inflorescence is an umbel or raceme that is composed of waxy or succulent flowers that are both attractive, unique and lightly fragrant. The flowers are produced on a peduncle (or ‘spur’). It is important not to prune off these peduncles when the plant is done flowering since more flowers will be produced on this same peduncle. Blooming will likely not occur until the plants are 2-3 years old.
Hoya flowers have a unique pollination strategy which involves having their pollen packed into ‘pollinia’ (sticky pollen sacks). These masses of pollen grains are bound together by a waxy substance and attached to a small, sticky disc called a ‘corpusculum’. This corpusculum sticks to the pollinator (ie. a moth or bird) and only un-sticks when the pollinator reaches a compatible flower. The compatible flower and pollinia fit together in an intricate way in order to release the pollen or… the compatible flower emits a specific chemical signal that triggers the release of the pollen.
Hoya houseplants are recommended for beginner indoor gardening enthusiasts, since they are easy to grow. Seasoned gardeners will enjoy growing hoyas because of the plant’s uniqueness and beauty. In nature, hoyas grow in high humidity areas however, their thick, succulent leaves makes them good survivors in the drier humidity of the Prairie home. Hoyas can dry out significantly between watering and still survive. In fact, healthy hoyas prefer to have the soil dry out between waterings: too much water and the roots will rot. An application of fertilizer once/ month is adequate. Compost tea or diluted fish emulsion will provide adequate fertility.
Hoya plants prefer 2-6 hours of bright indirect light each day, however, since they dwell in rain forests, they will survive in dappled light. Because of their vine-like growth pattern, hoya plants do well in hanging baskets, as trailing plants or growing on a trellis. The preference for high humidity conditions makes them excellent plants for terrariums.
Several popular species that are commonly available include Hoya carnosa, which is the most popular and common hoya to be found in plant shops. Hoya carnosa grows as long vines with thick, oblong medium green leaves that sometimes have flecks of white. Hoya australis, another common hoya, has thinner, rounder leaves than Hoya carnosa. Hoya pubicalyx has narrower, attractive green leaves with white flecks. Hoya kentiana has narrow bean-shaped hoya leaves that are rimmed it dark green and maroon. Hoya kentiana is a more rare hoya to be found in the houseplant market.
Hoya kerrii is often referred to as a Valentine hoya due to its thick heart-shaped leaves. Hoya retusa is a unique type in that it has thin, stick-like foliage. Hoya retusa is low maintenance, easy to grow and really shows off its beauty in a hanging pot. Hoya fitchii is worth mentioning for its large attractive green leaves with delicate white veining. When Hoya fitchii blooms, the flowers are coral, pink and yellow with a sweet aroma. Hoya fitchii prefers more bright light than some of the other hoya types.
There are many more hoya species available as houseplant than are mentioned in this article. Research has shown that hoya plants are useful in improving indoor air quality and cleansing the air. Hoyas are not toxic to pets although they may cause some stomach upset and diarrhea to your pet if ingested. Some hoya plants secrete a latex substance when damaged: this latex can be a skin irritant to humas. In the past, hoyas have been used medicinally in Polynesian culture.
This column is provided courtesy of the Saskatchewan Perennial Society (SPS; saskperennial@hotmail.com). Check our website (www.saskperennial.ca) or Facebook page (www.facebook.com/saskperennial) for a list of upcoming gardening events.
