Plant records · Direct sun
Hoya carnosa: why your wax plant will not flower
Hoya carnosa is easy to grow and hard to flower, and the reason is almost always the same: the grower cut off the flowering spurs. Hoya produces its scented porcelain-flower clusters from short woody spurs, and those spurs re-flower year after year if you leave them alone.
Hoya carnosa · Apocynaceae
| Botanical name | Hoya carnosaApocynaceae |
|---|---|
| Light | 1,500-6,000 lxDirect sun |
| Humidity | 40-70% |
| Watering | Every 13 days |
| Drainage | Loose and airy epiphyte mix: 40% orchid bark, 30% perlite, 20% coco coir, 10% worm castings. Hoya is a climber in tree crotches, not a plant of forest floor soil. |
| Mature height | 300 cm |
| Growth rate | Moderate: 30-90 cm of vine per year once mature. Plants from seed take three to five years to flower; cuttings from a flowering plant can flower in their second year. |
| Propagation | Cuttings from a flowering stem, rooted in water, perlite or sphagnum. Use a section with at least two nodes. Cuttings taken from non-flowering growth take much longer to flower. |
| Pet safety | safeConsidered non-toxic to cats and dogs by the ASPCA. The milky sap can irritate sensitive skin, but ingestion is not a poisoning risk. |
presentationWhat you are seeing
- A large, healthy, glossy plant that has never flowered — sometimes for ten years.
- Flower buds that form and then dry up and drop before opening, a condition growers call bud blast.
- Long vines with wide spacing between leaves and no sign of flowering, on a plant that has been moved around the house.
aetiologyWhy it happens
- The commonest cause of a non-flowering Hoya is pruning off the flowering spurs. They look like dead stubs — short, woody, leafless — and are routinely tidied away in autumn. Each spur is the site of next year's flowers and cutting it removes the flowers permanently at that point.
- Bud blast is caused by a change in conditions while the buds are developing: moving the plant, a draught, a sudden temperature drop at night, or letting the mix dry out completely during bud development. Hoya buds are intolerant of any change at that stage.
- Wide leaf spacing and no flowering means insufficient light. Hoya carnosa needs 1,500 lx minimum to flower and does best with several hours of direct morning or late-afternoon sun.
managementWhat to do
- Stop pruning. Never cut a leafless woody spur off. If you have already cut them, expect two to three years before new spurs mature enough to flower.
- Move the plant to a spot with 1,500-6,000 lx including some direct sun — an east window with three hours of morning sun, or a west window with late-afternoon sun. Acclimate gradually if it has been in shade.
- Let the plant become slightly root-bound. Hoya flowers best in a pot that is nearly full of roots; repotting into a larger pot resets flowering for a year or more. Repot only when roots are coming out of the drainage holes.
- Leave the plant in one place once buds appear. Do not move it, do not turn it, do not repot it, and keep the watering consistent. Bud blast is nearly always a response to a change made during development.
- Water when the top 3 cm of mix is dry, roughly every 13 days in summer. Hoyas are more tolerant of dry than wet; in winter go to three weeks or more.
What a flowering spur looks like
A Hoya flowering spur is a short, woody, knobbly stub, usually 1-3 cm long, growing out from the main stem at a leaf axil. It has no leaves. After flowering it stays on the plant, and the next season's buds emerge from the same spur.
With each flowering year the spur gets slightly longer and knobbier, and a mature plant can carry twenty or more. This is why an old Hoya that has been left alone flowers far more heavily than a young one that has been tidied.
- Appearance: short, woody, leafless, knobbly
- Length: 1-3 cm, growing a few mm each year
- Position: at a leaf axil on the main stem
- Lifespan: the life of the plant, if not cut
- Never prune them in autumn cleanup
Light, temperature and the flowering trigger
Hoya carnosa flowers most reliably after a cool, bright winter during which it receives a few hours of direct sun and less water. A plant kept at a constant 22 C in a dim room with even watering has no seasonal signal to flower.
A practical routine: summer outdoors in dappled sun or at an east window, watered and fed normally; winter at 13-16 C, watered every three to four weeks, no feed. Flowering usually follows in late spring or summer.
The sap and the scent
Hoya carnosa is non-toxic, which makes it an unusually good choice for a household with cats or dogs. Its one drawback is the milky sap that bleeds from any cut: it is sticky, sets hard, and can irritate sensitive skin. Wear gloves when taking cuttings and clean the blades afterwards.
The flowers of Hoya carnosa are strongly scented at night and can be overwhelming in a small bedroom. If the plant flowers in a bedroom and you find it too much, moving it while in bud risks bud blast, so wait until after the flowers fade before relocating it.
Sheets that reference this plant
| Leggy, stretched growth | Leggy growth is a plant's rational response to insufficient light: it invests in stem rather than leaves because stem is what gets it closer to the… |
|---|---|
| Sudden leaf drop | A plant that loses a third of its leaves in a week looks like an emergency, but in most cases it is a controlled response rather than a disease. The… |
| Spots and blotches on leaves | Leaf spots are the symptom most often misdiagnosed as disease when they are caused by water, sun or the plant's own physiology. The decision path is… |
| Pale or white new growth | New growth coming through pale is either a light problem or a nutrient problem, and the two look nothing alike once you know the pattern. Etiolation… |
Troubleshooting
My Hoya has never flowered. What am I most likely doing wrong?
The buds dried up and fell off before opening. Why?
Is Hoya carnosa really safe around cats?
CaveatCare information only. Listed as non-toxic to cats and dogs, but contact a veterinarian with any concern about ingestion rather than relying on this page.
Published2026-10-02 ·