Hoya soligamiana

Meet the plant

A hoya found only in the Philippines (Kew POWO), discovered in 2006 at about 200 m in Atimonan, Quezon Province, on Luzon, and described in 2009 (Vermont Hoyas, soligamiana, Kloppenburg, Siar and Cajano). It is a climbing or trailing epiphytic vine with long, dark green, slightly succulent leaves marked with pale veins and drawn out to a fine point (Foliage Factory). New leaves come in brick red and green up as they grow. It is still rarely offered.

Little has been written about growing it. What there is points to a warm, humid grower: it comes from lowland forest, not the cool mountains some hoyas call home, and Foliage Factory asks for high humidity and bright light (Foliage Factory). Vermont Hoyas grows it in a semi-hydro setup, where it puts out a lot of new growth (Vermont Hoyas, soligamiana). Most of the care below is general hoya advice from the extension pages and growers, adjusted for warmth and humidity; read it as a sensible starting point rather than settled knowledge for this species. This guide calls it moderate, for the humidity it wants.

No poison-centre list names it; the ASPCA lists its relative the wax plant as non-toxic to cats and dogs (ASPCA). Hoya 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: at an average pace, new pairs of leaves along vines that reach out bare and leaf up behind (Foliage Factory), little in winter, and perhaps flowers, since it can bloom young (Vermont Hoyas, soligamiana).

Light

Bright, indirect light, close to an east or west window; gentle morning or evening sun is fine once the plant is used to it (Foliage Factory). Move it into stronger light over a couple of weeks, not in one go (Clemson HGIC).

Too much sun shows as bleached or scorched patches (Iowa State Extension). Too little shows as long stretched vines with small leaves far apart, and no flowers; light is the first thing to change when a hoya will not bloom (UF/IFAS Gardening Solutions).

Water

Check first. Push a dry finger as far into the mix as it will go, and lift the pot: learn what it weighs wet and dry (Vermont Hoyas, watering, Clemson HGIC). Dry all the way down and light means it is time. Any dampness means wait. Leaves that feel softer than usual are asking.

The rule: water thoroughly, until it runs out of the bottom, once most of the mix has dried, then let it dry again. Foliage Factory waits until the mix is 60 to 80 percent dry (Foliage Factory); Iowa State says let a hoya's mix dry almost completely (Iowa State Extension). This guide takes the drier end of that. Water through, never in sips, and empty the saucer (Vermont Hoyas, watering). The humidity this plant likes belongs in the air around it, not in a wet pot.

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 vine (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 chunky mix in a bright, warm room in summer it often comes round every week or two; no source gives a figure for this species, and most hoyas need water no more often than about every six days (Vermont Hoyas, watering). In winter, with less light, it wants less (UF/IFAS Gardening Solutions), though dry heated air can empty a pot faster than you expect. Treat the numbers as a reminder to check, not as the instruction.

Soil and pot

An airy, fast-draining, bark-based mix of medium chunkiness that still holds a little moisture (Foliage Factory): equal parts orchid bark, peat-free compost and coarse perlite does it (RHS growing guide, Clemson HGIC). Every mix breaks down over two or three years into fine material that holds water, so refresh it on that rhythm (Vermont Hoyas, medium).

The pot needs a drainage hole and should be snug; a pot too large keeps the mix wet (Clemson HGIC). Give the vines a support to climb, as Foliage Factory recommends, or let them trail from a hanging pot. When you do move up, go one size, 2 to 4 cm wider (Vermont Hoyas, repotting). Plastic holds moisture longer and lets you judge the weight, which suits a plant that likes humidity.

Repot in spring, never in bud or bloom (RHS growing guide). Soak it in, then wait until the new mix is nearly 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.

Feeding

Lightly. A balanced liquid houseplant or orchid feed at half strength every four to six weeks from spring to early autumn, and nothing in winter (Iowa State Extension). No source gives a rule for this species; the RHS feeds hoyas more often, every couple of weeks in summer and monthly in winter (RHS growing guide), and this guide takes the weaker rule. Every few months water through with plain water to wash out salts.

Flowering

Hanging clusters of star-shaped flowers that stand out from the buff flowers of many hoyas (Vermont Hoyas, soligamiana): growers describe golden-yellow stars, folded back, with a hot-pink centre. It can flower young; Vermont Hoyas had a rooted cutting produce a flower stalk and bloom within about six weeks in its rooting chamber. Foliage Factory says it flowers indoors with bright light, warmth and a steady routine (Foliage Factory).

Two things never to do. The flowers come again from the same spurs, so leave them on the vine when the flowers fall (RHS growing guide, UF/IFAS Gardening Solutions). And once buds appear, do not move or turn the plant until the flowers are over; a moved hoya drops its buds (Iowa State Extension).

When something looks wrong

Look at the soil first, then at the warmth and the air.

• Soft, dull or wrinkling leaves. Check the mix. Dry and light: soak it. Wet: let it dry almost completely and slide it out to look at the roots (Iowa State Extension).
• Leaves yellowing and dropping. A wet pot first; otherwise a cold window or draught, or dry air (RHS growing guide). Correct the water, keep it above 15 C and off cold glass, and raise the humidity.
• Yellow leaves on wet mix. Overwatering, a pot too large, or a mix that has broken down (Clemson HGIC). Stop until nearly dry, check that water runs freely out, and repot into fresh airy mix if the mix is compacted.
• Brown crisp tips or edges. Dry air. A humidifier, a pebble tray or grouped plants, and distance from the radiator.
• Scorched patches. Direct sun on a plant not used to it (Clemson HGIC). Move it back and introduce stronger light gradually.
• Long bare vines. Partly normal, since a hoya sends a runner out first and leafs it later; very long gaps mean too little light (Iowa State Extension).
• No flowers. Light first, then warmth, then the spurs: were they cut? (UF/IFAS Gardening Solutions, Foliage Factory)
• Buds drop before opening. The plant was moved, or the watering or temperature changed suddenly (Iowa State Extension). Leave it where it is.
• 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, vines 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 vine straight away: a plant this far gone often does not recover (RHS growing guide).

Propagation

By stem cuttings, in spring or summer. Take a piece of mature but not woody vine with two or more nodes and a couple 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 make a vine (Iowa State Extension). Warmth matters more for this lowland species than for most; a spot above 20 C speeds rooting.