This post is all about Hoyas: how to care for them and how to make them flower.
Hoya is a genus of plants native to Australasia, Asia, and the Pacific. It boasts a staggering 200-300 species. The genus is part of the larger Apocynaceae family which includes flowering shrubs like jasmine. Each species has flowers and leaves of different colors, sizes, and shapes.
Hoya leaves come in varying shapes. The hoya compacta (rope plant) has interesting curled leaves. Kor!An (Андрей Корзун) https://commons.wikimedia.org/wiki/File:Hoya_compacta_12.jpg
Hoya have surged in popularity in recent years, competing with orchids as the prime indoor flowering species. They are not as fiendishly difficult as some orchid species but do have particular care needs that lend themselves to a niche fascination among indoor gardeners.
Hoya's glassy geometric flowers and tropical foliage heighten their appeal. One species is called the 'Hoya Bella' - simply, beautiful Hoya. One garden writer in the 19th century said it is 'the most lovely of all the Hoyas, resembling an amethyst set in silver'.
A search for Hoya on the National Gardening Association Database yields almost 600 entries - this includes both species and varieties. It is difficult to say how many of these Hoya species you can get hold of garden centers as some may be quite rare. Hoya can easily become an absorbing collector's hobby if you want to amass a collection of unusual species.
Many Hoya species are epiphytic meaning they grow on the surface of other plants. Here you can see the trailing vines of hoya lacunosa hanging off a tree trunk. Maja Dumat https://commons.wikimedia.org/wiki/File:Wachsblume_(Hoya_lacunosa).jpg
Hoya carnosa is the most common hoya species in gardening stores. They are low maintenance and are a good option to start out.
Hoya carnosa JLPC https://commons.wikimedia.org/wiki/File:Hoya_FR_2013.jpg
Hoya lacunosa is slightly less common in gardening stores but it is equally suitable for beginners. Hoya Pubicalyx is another low-maintenance species as long as you can provide high humidity levels (60-70%)
Hoya lacunosa B.traeger https://commons.wikimedia.org/wiki/File:Hoya_lacunosa.JPG
Hoya shepherdii has very long and thin leaves is generally easy to take care of, with less humidity required than most other species.
Hoya shepherdii. Walter https://commons.wikimedia.org/wiki/File:Hoya_shepherdii_(14396845459).jpg
Hoya bella is as demanding as it is beautiful. It demands a delicately balanced watering regime and specific soil. It needs very light and bark-rich soils to mimic its tree canopy natural environment - it grows in the wild hanging off of trees. The bark should be almost dry with a hint of moisture at all times. It also needs cool night-time temperatures of around 50 degrees Fahrenheit.
Hoya Bella. 阿橋 HQ https://commons.wikimedia.org/wiki/File:美麗毬蘭_Hoya_bella_-香港公園_Hong_Kong_Park-_(9240227808).jpg
Hoya linearis is considered one of the most difficult hoya to grow as you need to get the watering and humidity just right.
Hoya linearis. 阿橋 HQ https://commons.wikimedia.org/wiki/File:線葉毬蘭_Hoya_linearis_-香港公園_Hong_Kong_Park-_(29886352712).jpg
Many Hoya species need very infrequent watering. This applies especially to the species with fleshy leaves. The leaves store moisture so it is very easy to over-water these. For these species, always let the top two inches dry out in summer before watering - test soil moisture first by sticking your finger into the soil. In winter, don't water unless the soil is completely dry.
When you water Hoya, run the pot under a tap until the water is running through the drainage holes. This ensures an even watering that soaks the soil completely and flushes excess fertilizer from the soil.
There are a few Hoya species that need more frequent watering. This includes the Hoya multiflora and other thin-leaved Hoya which are not succulents. For these, make sure the soil is a little moist at all times.
The most difficult Hoya species will need a very precise amount of moisture present in the soil. This can make watering tricky. Hoya brevialata and Hoya polyneura need soil that is constantly and evenly moist but not waterlogged or very wet. You can achieve this delicate balance by making sure that you are using a potting mix with a high percentage of bark and perlite. These materials are loose and open, ensuring high drainage so no water is ever sitting around too long in the container.
Many Hoya - Hoya Bella, Carnosa, compact, kerii, fungi, longifolia, obocata, polyneura, sheperdhii - grow in medium temperatures between 60 and 65 degrees Fahrenheit during the day and 55 to 60 degrees Fahrenheit at night.
Other Hoya need warm temperatures no lower than 70 degrees Fahrenheit, such as the hoya ruscifolia, montana, patella, subcalva, cominsii. These will even thrive in temperatures over 95 degrees Fahrenheit.
Hoya appreciate very well-draining soil. This means soils that have lots of air pockets and let water through very quickly.
An ideal mixture for hoya is one part orchid bark, one part peat-free compost, and one part coarse perlite. Orchid bark has large loose particles that maintain air pockets around plant roots. Perlite is made up of light volcanic mineral particles that are full of air holes, retaining moisture while ensuring high drainage. The compost will give added moisture retention and nutrients.
Bark chips are an essential ingredient of hoya potting mixes https://pxhere.com/en/photo/1610592
This basic mixture can be adjusted to suit the particular needs of different hoya species. For example, Hoya Bella, kentiana, and Wayetii will appreciate a potting medium that has a lot of bark.
High humidity is absolutely crucial for healthy Hoya. These plants are native to rainforests where the atmosphere is constantly sticky. Most hoya need over 60% humidity for optimal health.
To achieve higher humidity around plants in your home, place the pot in a tray of gravel half-filled with water (making sure that the water line never touches the bottom of the pot) and mist the leaves with a bottle spray each day.
Other species need these high levels of air moisture just to survive, such as the hoya wayetii and hoya patella. The easiest way to grow these is in a greenhouse or conservatory.
Some species can tolerate lower humidity. Hoya kentiana can do with as little as 40%. Hoya obovatas, Hoya shepherdii, and Hoya carnosa can also thrive in moderate humidity.
Hoya need little fertilizer as they are slow growing. Give a half-strength dose of balanced fertilizer every four or six weeks during spring to late summer. Do not fertilizer during the winter.
If you are waiting for flowers, use a phosphorus-rich fertilizer. Read on for more on how to get your hoya to flower.
How to get your Hoya to flower
Many people bring home a Hoya from the garden store, only to find themselves admiring their deep green leaves for months on end. Unfortunately, hoya do not flower in the first two years of its life. Hoya only bloom when the plant is mature. This can take at least two years.
Once the plant is mature, you need to give your hoya the following conditions to encourage flowering:
- A pot that is slightly too small for its roots. If you want flowers, do not repot the hoya unless the soil is extremely compacted. This means that unless there is a gap between the soil and the container, the soil is extremely hard, or roots are growing out of the drainage holes, you do not repot. It is very likely that you will not need to repot your hoya in the first two years of its life. Come maturity, usually in the third year, a root-bound hoya is much more likely to produce flowers.
- Enough light. The hoya needs bright but indirect sunlight. While it can survive in shade, a hoya in a shaded position will not produce flowers. The ideal position to get your hoya flowering is a South facing window with net curtains or a large tree right outside to dapple the sunlight. The shade is very important: the hoya does not like direct sunlight. This will scorch its leaves.
- Correct watering. Give only a minimal amount of water while you wait for it to produce flowers. Once flower buds start to form, water it slightly more - never let the soil dry out completely at this stage.
- Fertilizer. Give very minimal fertilizer to your Hoya if you want it to flower. A half-strength dose of phosphorus fertilizer every month in spring and summer is enough. A phosphorus fertilizer contains slightly more phosphorus than the other two macronutrients, which are nitrogen and potassium. This type of fertilizer is designed for flowering plants. Half-strength just means using half the amount of fertilizer that the packaging recommends. Do not fertilize at all in winter.
- A stable location. Avoid moving your plant around at all costs especially in the lead-up to flowering. Hoya are very fussy on this point and they do not take kindly to changes in their environment.