Krimson Queen (Hoya carnosa 'Krimson Queen')

Meet the plant

The variegated wax plant: thick, glossy leaves with a green centre and a broad margin of cream to white, flushed pink when young, on brownish stems (NC State Extension, RHS profile, Epic Gardening). It was patented in the 1950s as 'Tricolor' and is now mostly sold under the name 'Krimson Queen' (LLIFLE); the RHS treats the two names as one plant and gives it an Award of Garden Merit (RHS profile, RHS growing guide).

It is easily confused with its mirror image, 'Krimson Princess', which has a green edge around a cream-pink centre and pinkish-red stems (NC State Extension, Epic Gardening). Some shops and care guides swap the names. If the cream is on the outside, it is the Queen.

Everything that holds for the wax plant holds here, with two differences. The cream part of each leaf makes no food, so the plant grows more slowly than the green form (LLIFLE); and it is more particular, wanting very bright light and being particularly sensitive to overwatering (Pistils Nursery). It is still a forgiving plant: growers say a carnosa takes a lot of neglect, and that overwatering is the one thing that really harms it (Vermont Hoyas, carnosa). The ASPCA lists the wax plant as non-toxic to cats and dogs (ASPCA); the milky sap can irritate skin, so wear gloves when you cut it (RHS growing guide).

What to expect in a year: a few new pairs of leaves and a runner or two in spring and summer, the newest leaves the prettiest with their wide pink margins, very little in winter, and probably no flowers yet. Flowers usually begin when the plant is two or three years old, often later (NC State Extension).

Light

Very bright, indirect light, close to an east or west window, with no hot sun on the leaves (Pistils Nursery, NC State Extension). Sources disagree on sun. The RHS lists a sunny aspect for the cultivar and LLIFLE finds that strong light bronzes the leaves and encourages flowers (RHS profile, LLIFLE); Pistils says no direct sun, and Epic Gardening finds the Queen more prone to scorching than its relatives and grows it behind a sheer curtain (Epic Gardening). The cautious path is the brightest indirect light you have, a sheer curtain where the sun reaches the leaves, and any stronger light introduced over a couple of weeks (Clemson HGIC).

The margins are the gauge. Low light reduces variegation (Clemson HGIC): new leaves come in greener with a thin edge, and a leaf keeps the margin it was born with even after you move the plant. Too much sun burns the cream first, because it has no green to protect it; a pink flush in good light is harmless. Too little light also means no flowers (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. The leaves tell you too: growers wait until the leaves pucker slightly (Pistils Nursery).

The rule: water thoroughly, until it runs out of the bottom, once the mix is almost dry, then let it dry again (Iowa State Extension). Do not water in sips (Vermont Hoyas, watering), and use room-temperature water; cold water shocks the plant (NC State Extension). Sources differ on how dry is dry: the RHS waters freely in the growing season (RHS profile), while the American extension pages say let the mix dry almost completely. This guide takes the dry side, because this form is particularly sensitive to overwatering and its roots are easily lost in a pot that stays damp (Pistils Nursery, LLIFLE).

Thirsty: leaves puckered, soft and dull, on a dry, light pot. A soak brings them back over a day or two. Overwatered: leaves yellowing or dropping while the mix is still wet, or wrinkled leaves on wet mix, which means damaged roots (Iowa State Extension, NC State Extension). 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 bright light in summer it often comes round every week or two, as for the green wax plant; most hoyas need water no more often than about every six days (Vermont Hoyas, watering). In winter the plant rests and wants water very sparingly (UF/IFAS Gardening Solutions); LLIFLE keeps it dry with good airflow and suggests roughly a monthly watering (LLIFLE), Vermont Hoyas treats carnosa almost as a succulent then (Vermont Hoyas, carnosa), and the RHS keeps it just moist. A pot by a radiator can dry faster than you expect, but 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). Hoya growers go chunkier still, mostly perlite and bark with some compost (Vermont Hoyas, medium). Every mix breaks down over two or three years into fine material that holds water, so refresh it on that rhythm even if the pot stays the same.

The pot needs a drainage hole and should be snug. A hoya flowers better slightly pot-bound, and a pot too large keeps the mix wet and rots the roots (Iowa State Extension, Clemson HGIC). Carnosa types can stay in the same pot for years (Vermont Hoyas, repotting). When you do move up, go one size, 2 to 5 cm wider. Plastic lets you judge the weight; Vermont Hoyas finds bare terracotta dries a chunky mix too fast. Either works if you check before you water.

Repot in spring, never while the plant is 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). LLIFLE goes further and repots into dry mix, holding water until growth shows (LLIFLE); either way, the weeks after a repot are a time to water with care. Hold the feed for five or six weeks (RHS growing guide).

Feeding

Lightly. A balanced liquid houseplant or orchid feed at half strength every four to six weeks from spring to early autumn (Iowa State Extension). Sources disagree about winter: the RHS keeps feeding monthly through autumn and winter (RHS growing guide), while Iowa State stops for the rest. This guide stops, the weaker rule. Epic Gardening finds the Queen sensitive to overfeeding (Epic Gardening), which is one more reason to stay weak. Every few months water through with plain water to wash out salts (RHS growing guide).

Flowering

Rounded clusters of small waxy stars, pale pink, scented at night, from late spring to autumn (RHS profile); Epic Gardening describes the Queen's flowers as pink throughout, where the Princess's have a deep red centre (Epic Gardening). They drip nectar, so put a cloth under a plant in bloom (LLIFLE).

What it takes: a plant two or three years old or more, very bright light, a snug pot, and a cooler, drier, unfed winter (NC State Extension, Iowa State Extension). Carnosa is a late bloomer and many growers wait years (Vermont Hoyas, carnosa); with less green to work with, this form may take longer.

Two things never to do. The flowers grow from short spurs, and the same spur flowers again year after year. When the flowers fall, leave the spur alone: cutting it off is cutting off future flowers (NC State Extension, LLIFLE, RHS growing guide). And once buds appear, do not move or turn the plant until the flowers are over; a moved plant drops its buds (LLIFLE, Iowa State Extension).

When something looks wrong

Look at the soil first, then at the margins.

• New leaves greener, margins narrower. Too little light (Clemson HGIC). Move it to very bright indirect light; new leaves come in variegated again, while grown ones keep the margin they have.
• Cream margins browning or crisp. Direct sun burns the margin first (Epic Gardening); a wet mix or very dry air can do the same. Filter the light, check the mix, raise the humidity in winter.
• Puckered, wrinkled or soft leaves. Check the mix. Dry and light: soak it through and the leaves plump up over a day or two. Wet: the roots are damaged; let it dry almost completely and slide it out to look (Iowa State Extension).
• Yellow leaves on wet mix. Overwatering, which this form tolerates less than the green one, a pot too large, or a mix that has broken down (Pistils Nursery, Clemson HGIC). Stop until nearly dry, check that water runs freely out, and repot into fresh airy mix in a snug pot if the mix is compacted.
• Leaves dropping. Too wet, too dry for too long, cold water, or a cold, draughty window (NC State Extension, RHS growing guide, Pistils Nursery). Correct the water, move it off cold glass, keep it above 13 C.
• Pink young leaves. Normal, and the plant at its best; the pink fades to cream as each leaf matures (RHS profile).
• A shoot of all-cream or all-pink leaves. Fully white leaves are typical of this cultivar now and then (Epic Gardening). With no green they make little food and usually grow weakly; if such a shoot slows the plant, cut it back to a node with variegated leaves.
• No flowers. Light first, then patience, then the spurs: were they cut? Stop feeding in winter and give it a cooler rest (Iowa State Extension).
• Buds drop before opening. The plant was moved, the watering changed, or the temperature swung (LLIFLE, Iowa State Extension). Leave it where it is until it has finished.
• Mealybugs. White cottony tufts in the leaf joints (LLIFLE, RHS profile). Dab each one with a cotton bud in rubbing alcohol, wash with insecticidal soap, repeat weekly for several weeks, and keep the plant apart until clear (Clemson HGIC).
• Scale. Small hard brown bumps with sticky residue (RHS profile). Wipe or scrape them off, then wipe with insecticidal soap or horticultural oil and repeat.
• Spider mites. Pale speckling and fine webbing in dry warm air, often by winter heating (Clemson HGIC, NC State Extension). Shower the plant, undersides included, every few days, spray with insecticidal soap or neem weekly, and raise the humidity.
• Black mushy base, 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 variegated vine straight away: a plant this far gone often does not recover (RHS growing guide).

Propagation

By stem cuttings, in spring or early summer, and they root easily (LLIFLE). Choose a piece of vine whose leaves are well variegated, mature but not woody, with two or more nodes; a cutting from an all-green or all-cream shoot grows on that way. Wear gloves for the sap. Stand it in water, where it roots in two or three weeks, then pot it up (RHS growing guide); or push it into moist perlite up to the first leaves, keep it warm and humid in bright indirect light, and expect roots in four to six weeks (Vermont Hoyas, propagation). A leaf on its own needs a node attached to make a vine (Iowa State Extension). The RHS also layers it: pin a length of stem to a pot of mix beside the plant and cut it free once rooted (RHS profile).