Hoya curtisii

Identification

Hoya curtisii is one of the small-leaved hoyas. In the original description, King and Gamble called it a small twining epiphyte that roots at almost every node, on tree bark or on rocks, with slender, hairy young stems ^[1]. A 2022 paper describes it as a creeper that grows pressed tightly against the host trunk ^[2].

The leaves sit almost directly on the stem and are very thick. They are round with an abruptly pointed tip and a thickened margin, and the protologue gives 0.4–0.7 in long by 0.4–0.6 in wide (about 1–1.8 × 1–1.5 cm) ^[1]. When dried, only a faint midrib shows and the other veins are invisible ^[1]. Rodda and Rahayu give the leaves as round or broadly ovate, under 2 cm long and up to 3 mm thick ^[2]. In the typical subspecies they are mid to dark green with prominent gray markings and turn maroon in strong light ^[2]. NParks describes dull green leaves with silver markings that redden in very bright light ^[4].

The umbels have no stalk and hold 10–16 flowers on hairy pedicels of 0.75–1 in (about 2–2.5 cm) ^[1]. The flower clusters grow upward, away from the ground ^[2]. The corolla is strongly reflexed, finely hairy, and has a ring-shaped outgrowth near its base. The staminal corona lobes are nearly globular and rise above the column ^{[1, 2]}.

Look-alike. Hoya serpens also has tiny, near-round leaves on creeping stems, but its umbels are carried on long peduncles ^[6]. In H. curtisii they sit directly on the stem ^[1].

Naming and trade labels

The accepted name is Hoya curtisii King & Gamble, published in 1908 and named for Charles Curtis, who collected the type in Perak ^{[7, 1, 5]}. WCVP accepts two subspecies ^[3]. The typical subsp. curtisii is the widespread plant. Subsp. collariata, described in 2022, is known only from lowland heath forest in Central Kalimantan, Borneo. It has a corolla hairless inside and erect, flattened corona lobes ^[2]. Dried leafy specimens of the two are almost indistinguishable, though fresh leaf color may separate them ^[2].

NC State lists several common names, including porcelain flower, tiny leaf porcelain flower hoya and wax flower ^[5]. None of the institutional sources consulted mentions named cultivars.

Growing it

NC State publishes care notes written for this species, and NParks lists basic conditions.

• Light. Give bright, indirect light for at least six hours a day, but avoid direct sun, which scorches the leaves ^[5]. NParks lists semi-shade ^[4]. See the light guide.
• Water. NC State describes the plant as drought tolerant and very sensitive to overwatering. Water thoroughly, then let the mix dry out ^[5]. NParks lists moderate water with occasional misting ^[4]. See the watering guide and root rot.
• Humidity and temperature. NC State recommends 50–60% relative humidity and gives 60–80°F as the range for good growth ^[5]. It does not state a minimum. See the humidity guide.
• Mix and pot. Use a well-drained, slightly acidic mix rich in organic matter, with perlite or vermiculite added. Repot every 2 or 3 years; plants bloom better somewhat rootbound ^[5]. See the substrate guide.
• Growth and training. NC State describes a slow-growing, clinging vine, 2–3 inches tall and 1–3 feet long, that can hang from a basket or climb a moss pole ^[5]. See trellising.
• Pests. NC State names aphids, spider mites, scale and mealybugs ^[5]. See hoya pests.

ASPCA does not list H. curtisii.

Flowering

NParks and NC State both describe the flowers as fragrant ^{[4, 5]}. NC State says the plant usually blooms in summer, that the flowers can last several weeks, and that it reblooms from the same peduncles for several years, so these should not be pruned off ^[5]. See hoya peduncles and why a hoya is not blooming.

Notes on sources

The sources disagree on several points. On flower color, NParks gives cream, pale yellow or lime-green petals with a white corona ^[4], while NC State describes pink or red petals with a white center ^[5]. This page follows NParks for the color filter. The botanical descriptions do not settle it, since the protologue was written from dried specimens and gives no colors ^[1].

NC State also gives 6–10 flowers per cluster, green peduncles up to 2 inches long and leaves 1–2 inches long ^[5]. The protologue gives 10–16 flowers on stalkless umbels ^[1], and the 2022 paper gives a peduncle no more than 5 mm long and leaves under 2 cm ^[2]. The structured data on this page uses the botanical descriptions.