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Plant care

Hill Wax Plant (Wax plant) care

Hoya collina

Also called Hill wax plant, Wax plant.

RHS H1bUSDA 11–12Pet-safeIndoor Typically 50 cm–1.2 m in a container

Watering rhythm

10-14days

Every 10–14 days in the growing season; every 3–4 weeks in winter

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Light

Bright indirect light (just back from a sunny window)

Soil

Chunky, free-draining epiphyte mix

Humidity

50–70%

Temp

16–28 °C

Pet safety

Pet-safe

Mature size

Typically 50 cm–1.2 m in a container

Care at a glance

Light

Bright but filtered. Hill Wax Plant burns within days in unfiltered south-facing summer sun, and stops growing within months in deep shade. A bright east- or west-facing window suits this species well; it can tolerate moderate light but will not flower without at least a few hours of bright, diffused light daily. If you only have a south window, set the plant back 1.5 m or hang a sheer curtain — both knock the intensity down into the right range.

Watering

Watering hill wax plant: every 10–14 days in the growing season; every 3–4 weeks in winter. The number that matters isn't the day of the week — it's how dry the top 2-3 cm of the pot feels. A finger in the soil tells you more than a watering app. After every watering, tip the saucer. Allow the top 3–5 cm of growing medium to dry before watering; yellowing or drooping leaves are the first signs of overwatering, while wrinkled leaves indicate thirst.

Soil and pot

Hill Wax Plant grows best in chunky, free-draining epiphyte mix. A blend of orchid bark, perlite, and a small amount of worm castings gives the drainage, aeration, and moderate nutrition this compact epiphyte needs. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Hill Wax Plant sits happiest at around 50–70% humidity and 16–28 °C (61–82 °F). Performs well at average indoor humidity of 50–60% but benefits from a pebble tray or regular misting of the aerial roots during the growing season. If you keep the room above 16–28 °C year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed hill wax plant sparingly. Feed monthly with a half-strength balanced liquid fertiliser from spring through early autumn; repotting is needed only every 2–3 years as the plant tolerates being slightly root-bound. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on hill wax plant in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Overwatering and root rot — This species is particularly sensitive to wet soil; yellowing, mushy, or drooping leaves signal root rot — check the roots, trim any blackened sections, and repot in fresh dry mix.
  • Mealybugs in leaf axils — Waxy white cottony deposits tucked between leaves and stems are a sign of mealybugs; dab each cluster with isopropyl alcohol on a cotton swab, then follow up with neem oil spray.

Propagation

Take stem cuttings just below a node and root in moist sphagnum moss or a perlite/coco coir blend at 22–25 °C; avoid bottom heat above 27 °C, which can encourage rot before roots form. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Hill Wax Plant is pet-safe. The ASPCA classifies the Hoya genus as non-toxic to dogs, cats, and horses; no toxic principles are identified. Ingestion of large amounts may still cause mild gastrointestinal upset. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Hill Wax Plant care — frequently asked questions

What is the common name for Hoya collina?

Hoya collina is most commonly called Hill Wax Plant, but it is also known as Hill wax plant, Wax plant. The names refer to the same species, so care instructions for Hill Wax Plant apply identically to anything sold as Wax plant.

How much light does hill wax plant need?

Hill Wax Plant grows best in bright indirect light (just back from a sunny window). A bright east- or west-facing window suits this species well; it can tolerate moderate light but will not flower without at least a few hours of bright, diffused light daily.

How often should I water hill wax plant?

Water hill wax plant every 10–14 days in the growing season; every 3–4 weeks in winter. Allow the top 3–5 cm of growing medium to dry before watering; yellowing or drooping leaves are the first signs of overwatering, while wrinkled leaves indicate thirst. The finger-test (or lifting the pot to feel its weight) beats a fixed weekly calendar because pot size, light, and season all change how fast the soil dries.

Is hill wax plant toxic to cats and dogs?

Hill Wax Plant is pet-safe. The ASPCA classifies the Hoya genus as non-toxic to dogs, cats, and horses; no toxic principles are identified. Ingestion of large amounts may still cause mild gastrointestinal upset.

What USDA hardiness zone does hill wax plant grow in?

Hill Wax Plant is rated for USDA zone 11–12 (indoor in most climates) and RHS hardiness H1b. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Hill Wax Plant deep-dive guides

Every aspect of hill wax plant care, each with its own calibrated guide:

Featured in these plant shortlists

Hill Wax Plant qualifies for 11 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

Related guides

Hill Wax Plant is also commonly called Hill wax plant or Wax plant.