Hoya (wax plant)

About Hoya (wax plant)

The wax plant is a climbing, tree-perching vine from Southeast Asia, Japan and Taiwan with thick, waxy leaves and, on plants a few years old, hanging clusters of up to 30 fragrant, porcelain-like star flowers (NC State). It was the hanging-basket plant of the 1970s and is back in fashion, with hundreds of species and cultivars collected like orchids (Penn State, Clemson). It is forgiving of neglect as long as it is never left wet, and it blooms from the same woody spurs year after year, so those spurs are never cut.

None of the Extension pages we opened give a hardiness range. It is a frost-tender tropical vine grown indoors everywhere, and it can summer outdoors in shade once temperatures stay above 60 F, coming in when nights fall below 50 F (Clemson, NC State).

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

Usually bought as a nursery plant or started from a stem cutting with one or two nodes rooted in water or moist mix (Iowa State, NC State).

Growing it indoors

• Light: Bright indirect light near an east, west or south window; low light gives thin growth, few flowers and lost variegation, while a sunny south window needs a slow acclimation so the leaves don't burn or redden (Clemson, Iowa State, NC State).
• Water: Water thoroughly with room-temperature water, then let the mix dry almost completely, judging by the weight of the pot or slightly puckered leaves; water less in winter and in low light (Clemson, Iowa State, Penn State). Overwatering is its biggest killer, so keep the pot small and chunky, and cold water shocks it (NC State).
• Humidity: It does best at 40-60 percent but tolerates ordinary rooms; very dry winter air invites spider mites, so a pebble tray or humidifier helps (Iowa State, Clemson, NC State).
• Temperature: Iowa State says 65-80 F with slightly cooler nights and nothing below 55 F; NC State brings outdoor plants in once nights fall below 50 F. Keep it off cold glass and away from vents.
• Feeding: Iowa State feeds an all-purpose fertilizer at a quarter to half strength every second or third watering in spring and summer and none in winter; Clemson prefers a liquid fertilizer with a 2:1:2 or 3:1:2 ratio to encourage bloom.
• Repotting: Only when it has clearly outgrown its pot or the mix has broken down, and never while it is budding or flowering; move up one pot size (no more than 2 in) since it blooms better slightly pot-bound (NC State, Iowa State, Penn State).

Soil

A chunky, fast-draining mix of equal parts potting soil, orchid bark and perlite in a pot no bigger than the roots need (Clemson, Iowa State).

Pot in a chunky, fast-draining mix of equal parts potting soil, orchid bark and perlite in a pot no bigger than the roots need (Clemson, Iowa State).

Feeding

• Spring and summer, while vines and buds are growing: all-purpose liquid fertilizer at a quarter to half strength, or a 2:1:2 or 3:1:2 ratio liquid fertilizer. Every second or third watering (Iowa State); Clemson prefers liquid feed over slow-release because the plant is watered so seldom. Water first.
• Fall and winter: none. Don't fertilize in winter (Iowa State).

A pot much larger than the root ball holds water too long and rots the roots, and cutting the flower spurs removes next year's blooms (Clemson, NC State).

Harvest

Blooms spring through fall, mostly in summer, once the plant is 2-3 years old, and each cluster lasts weeks (NC State, Clemson); let the spent flowers fall and never cut the short woody spurs they grew from, since they bloom again every year.

Varieties (10)

NC State, Clemson, Iowa State and Penn State name these cultivars and related species among hundreds.

Pests to watch for

Mealybugs, Twospotted spider mite, Scale insects, Fungus gnats

Diseases and problems

Root and crown rot, Leaf spot

In the kitchen

Safety: Not listed as poisonous to people or pets (NC State, ASPCA); cut stems ooze a sticky milky sap that is messy rather than harmful (NC State).

Pets: Non-toxic to dogs and cats (ASPCA, listed as wax plant, Hoya carnosa 'Krinkle Kurl'); NC State also tags it non-toxic for horses.