Hoya 'Mathilde'

Meet the plant

A garden hybrid of the common wax plant and the tiny Himalayan Hoya serpens (Vermont Hoyas, Mathilde, Steve's Leaves). It sits between them: small, round, leathery leaves about 2 cm long, glossy dark green speckled with silver, on thin stems that twine on a hoop or trail from a hanging pot (Tesselaar, Plant Addicts). It stays a manageable size, well under a metre or so in a pot (Tesselaar).

Its care sits between its parents too. Vermont Hoyas finds it not as easy as the wax plant and not as hard as serpens can be (Vermont Hoyas, Mathilde). From the wax plant it takes a tolerance for a dry spell and a dislike of wet roots (NC State Extension); from serpens, smaller leaves that hold less water and a liking for warmth and humid air, since serpens yellows and drops its leaves when kept cool and dry (Vermont Hoyas, serpens). Much of the advice here is general hoya advice and parent-based, because no extension service has written about the hybrid itself. This guide calls it moderate.

The ASPCA has no entry for the hybrid but lists the wax plant parent as non-toxic to cats and dogs (ASPCA); one nursery advises keeping hoyas away from pets anyway (Plant Addicts). The milky sap can irritate skin, so wear gloves when you cut it (RHS growing guide).

You will usually buy a rooted cutting in a small pot. What to expect in a year: a few new stems and a steady run of small leaf pairs through spring and summer, at a moderate pace (Tesselaar), little in winter, and perhaps the first flowers: it may take a year or two to flower properly (Tesselaar).

Light

Bright, indirect light, close to an east or west window (Plant Addicts, Tesselaar). A little gentle morning sun suits it, and Steve's Leaves grows it in partial sun (Steve's Leaves); hot afternoon sun scorches the leaves (Tesselaar). Move it into stronger light over a couple of weeks, not in one go (Clemson HGIC).

Too much sun shows as bleached or brown patches. Too little shows as thin, stretched stems and no flowers (Iowa State Extension, UF/IFAS Gardening Solutions); the silver flecking is likely sparser in dim light too, as it is on other speckled hoyas.

Water

Check first. Push a dry finger into the mix to the second knuckle and lift the pot: learn what it weighs wet and dry (Vermont Hoyas, watering, Clemson HGIC). Dry to that depth and noticeably lighter means it is time; damp means wait. The leaves help: when they feel soft rather than firm, the plant is asking (Plant Addicts).

The rule: water thoroughly, until it runs out of the bottom, once the top half of the mix has dried, then let it dry to that point again. Do not water in sips (Vermont Hoyas, watering). Sources differ on depth. Tesselaar waters deeply once the top 3 cm are dry and says to err on the dry side; Plant Addicts and Steve's Leaves let the soil dry out between waterings (Tesselaar, Plant Addicts, Steve's Leaves). This guide takes the top half: drier than the shallowest rule, because overwatering is the main risk, but short of bone dry, because the small leaves hold less than a wax plant's.

Thirsty: soft, dull, slightly wrinkled leaves on a dry, light pot. A soak brings them back within a day or two. Overwatered: leaves yellowing or dropping while the mix is still wet, a soft dark patch at the base of a stem (Iowa State Extension, Clemson HGIC). If the leaves say thirsty and the soil says wet, believe the soil and look at the roots.

How often that lands depends on the pot, the mix, the light and the room. In a small plastic pot of chunky mix in bright light in summer it often comes round about once a week; most hoyas need water no more often than about every six days (Vermont Hoyas, watering). In winter it wants less (Plant Addicts, UF/IFAS Gardening Solutions), though dry heated air can empty a pot faster than you expect (Vermont Hoyas, watering). In a cool room err dry. Treat the numbers as a reminder to check, not as the instruction.

Soil and pot

A chunky, fast-draining mix: equal parts orchid bark, peat-free compost and coarse perlite (RHS growing guide, Clemson HGIC), or a good orchid mix (Tesselaar). Hoya growers go chunkier, mostly perlite and bark with some compost (Vermont Hoyas, medium). Every mix breaks down in time into fine material that holds water, so refresh it every two or three years.

The pot needs a drainage hole and should be small and snug: it flowers best pot-bound (Tesselaar), and a pot too large keeps the mix wet (Clemson HGIC). Repot only when it outgrows the pot, usually every two or three years (Plant Addicts), one size up, 2 to 4 cm wider (Vermont Hoyas, repotting). Growers disagree on material: Plant Addicts likes terracotta for air, while Vermont Hoyas finds bare terracotta dries a chunky mix too fast and uses plastic. Either works if you check before you water.

Repot in spring, never while it is in bud or bloom (RHS growing guide). Soak it in, then wait until the top half of the new mix is dry before watering again: the first two months are when overwatering does the most harm (Vermont Hoyas, repotting). Hold the feed for five or six weeks (RHS growing guide).

Feeding

Lightly. A balanced liquid feed at half strength about once a month from spring to early autumn, and nothing in autumn and winter (Plant Addicts, Iowa State Extension). Tesselaar uses a diluted liquid feed in spring and summer and suggests a potash-rich feed to encourage flowers (Tesselaar). The RHS feeds hoyas every couple of weeks in summer and monthly through winter (RHS growing guide); this guide takes the weaker rule. Every few months water through with plain water to wash out salts.

Flowering

Round clusters of small, fuzzy stars, white to porcelain pink, with a sweet, syrupy scent (Tesselaar, Steve's Leaves, Plant Addicts), each with a small red centre. It flowers freely in spring and summer once settled (Tesselaar), and a well-grown plant in full bloom can be spectacular (Vermont Hoyas, Mathilde). Hoya flowers drip a little nectar; a cloth under the plant helps.

What it takes: a plant a year or two old, bright indirect light, a pot it has filled with roots, and a quieter, unfed winter (Tesselaar, Iowa State Extension). Most hoyas that never bloom are not getting enough light (UF/IFAS Gardening Solutions).

Two things never to do. The flowers come again from the same spot as last year's, so do not cut the spurs or the leafless tendrils they hang from (Tesselaar, RHS growing guide). And once buds appear, do not move or turn the plant until the flowers are over; sudden changes make a hoya drop its buds (Iowa State Extension).

When something looks wrong

Look at the soil first, then at the air around it.

• Soft, dull or wrinkled leaves. Check the mix. Dry and light: soak it and the leaves firm up within a day or two. Wet: let it dry to the top half and slide it out to look at the roots (Plant Addicts, Iowa State Extension).
• Leaves yellowing and dropping. A wet pot first; otherwise cool, dry air, which the serpens parent answers by dropping leaves (Vermont Hoyas, serpens), or a mix left bone dry. Correct the water, keep it above 15 C and off cold glass, and raise the humidity in winter.
• Yellow leaves on wet mix. Overwatering, a pot too large, or a mix that has broken down (Tesselaar, Clemson HGIC). Stop until the top half is dry, check that water runs freely out, and repot into fresh airy mix if the mix is compacted.
• Brown crisp tips. Dry air. A pebble tray of water under the pot, or a group of plants (Tesselaar).
• Scorched patches. Hot afternoon sun (Tesselaar, Plant Addicts). Move it back or filter the light.
• Few flecks, thin stretched stems. Too little light. Move it close to a bright window.
• No flowers. Light first, then age, then the pot (too large?) and the spurs (were they cut?) (Tesselaar, UF/IFAS Gardening Solutions).
• Buds drop before opening. The plant was moved, or the watering or temperature changed suddenly (Iowa State Extension). Leave it where it is until it has finished.
• Mealybugs. White cottony tufts in the leaf joints (UF/IFAS Gardening Solutions). Dab each one with a cotton bud in rubbing alcohol, wash with insecticidal soap, repeat weekly, and keep the plant apart until clear (Clemson HGIC).
• Spider mites. Pale speckling and fine webbing in dry warm air (Clemson HGIC). Shower the plant, undersides included, every few days, spray with insecticidal soap or neem weekly, and raise the humidity.
• Black soft base, stems wilting on wet mix. Root rot. Cut away every dark soft root, repot in fresh, barely damp mix in a snug pot, and take cuttings of healthy stems straight away: a plant this far gone often does not recover (RHS growing guide).

Propagation

By stem cuttings, in spring or early summer. Take a piece of mature but not woody stem with two or more nodes and a few pairs of leaves; wear gloves for the sap. Push it into moist perlite up to the first leaves, keep it warm and humid under a clear cover in bright indirect light, and expect roots in four to six weeks (Vermont Hoyas, propagation), or stand it in water, where hoya cuttings root in two or three weeks (RHS growing guide). A leaf on its own needs a node attached to grow (Iowa State Extension). Pot the rooted cutting into the chunky mix in a small pot; a few cuttings in one pot make a fuller plant sooner.