Botanical name: Hoya
Group: Tender houseplant/evergreen climber
Flowering time: Late spring to autumn
Planting time: Spring
Height and spread: Both 45cm (18in) by 4m (12ft)
Aspect: Bright light
Hardiness: Tender difficult
Hoyas are native to Indo-China, Indonesia and Australasia, and in this country they need to be grown in a warm bright room in the house or heated conservatory. The most commonly grown are Hoya carnosa and Hoya lanceolata ssp. bella (syn. H. bella).
Spring and summer
- Place in a sunny, light position, but shade from direct bright sun to avoid foliage scorch
- Water regularly and feed with half-strength high potash fertiliser every two weeks or so
Autumn and winter
- Make sure plants receive bright light
- Plants are relatively dormant and need only moderate watering from October to February. Water when the soil is fairly dry, but not dust dry
- Feeding can be reduced to once a month until growth resumes in spring
- In winter a minimum night temperature of not less than 10°C (50°F) for H. carnosa and 16°C -18°C (60-65°F) for H. bella
Do not move plants once flower buds form and do not remove the flower stalk (peduncle) after flowering as more flowers are often borne on the stumps of previous clusters.
Plants require a humid atmosphere – maintain good levels of humidity by standing the container on tray of gravel, expanded clay granules (Hydroleca) or recycled lightweight aggregate (Hortag) and keep moist, with the water level slightly below the surface of the gravel.
Re-pot in spring if needed, and do not feed for 5-6 weeks after re-potting.
Sharply draining, well aerated compost is essential for hoya to thrive. This can be made using one part by volume orchid bark, one part peat free compost and one part coarse perlite. Alternatively, use cactus compost but add some extra perlite.
Pruning and training
Hoya carnosa is a strong-growing climber and should be grown up a trellis or around a wire hoop. In a conservatory it can be trained along horizontal wires. H. bella is a small bushy plant best grown in a hanging basket.
Cut back or thin congested growth at the end of February.
Hoyas do not respond well to hard pruning and over-large plants are best replaced.
Hoyas can be increased in a couple of ways;
- Remove a few leaves and peg down a strong shoot into a pot of cutting compost
- Keep the compost moist until rooted
- Sever from the plant and pot up
- Take semi ripe cuttings of the previous year’s growth in spring or early summer
- Cuttings are also easy to root in water
H. carnosa ‘Variegata’: This hoya has creamy white margins to its succulent leaves with waxy night scented white flowers.
Hoya lanceolata ssp. bella (syn. H. bella): A succulent trailing plant with clusters of sweetly scented white flowers with purple centres.
Common problems encountered when growing hoyas include;
Leaf-drop, blackening of leaves and dieback of stems: may be due to poorly-drained or water-logged compost or being too cool during the winter.
Wilting and die back of the growth above ground: can be caused by overwatering or excessive application of fertiliser making the roots unable to absorb water owing to the excessive levels of salts in the soil.
Root rot: may occur as a result of overly wet or poorly drained compost. Plants can be rescued by taking cuttings as soon as the problem is noticed.
Failure to flower: possibly due to insufficient light.
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