Tropicals > Alocasia > Alocasia reginula > Alocasia reginula
Alocasia reginula
Origin: Alocasia reginula originates from the Southeast Asian Bornean jungles. It is documented as being collected by Missouri Botanical Gardens on October 16, 2000, from limestone cliffs in the Tabin Wildlife Reserve, Sabah, Kinabatangan District. Furthermore, its first recorded collection date was in the 1860s when English plant collectors were searching for undiscovered tropical specimens to take back to England.
Mike's
Opinion
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A striking specimen, Alocasia reginula has deep green to black foliage and light green petioles attached to its corm. True to its common name, Alocasia ‘Black Velvet’, it also possesses black velvet-textured leaves with contrasting silver veins. This plant can be slightly more challenging to grow, given its preference for high humidity levels and diffused light, as well as its tendency to lose leaves when not watered on time. If stressed, it also makes it a target for pests, such as mealybugs or spider mites. It also stays relatively small, only reaching 46 cm wide and 30 - 60 cm high, making it a gorgeous specimen that can be grown in small indoor or outdoor spaces. Overall, despite its care preferences, Alocasia reginula makes a unique houseplant for its beautiful foliage and compact growing habits.
Michael Pascoe, NDP., ODH., CLT., MSc. (Plant Conservation)
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| Family |
| Araceae |
| Genus |
| Alocasia |
| Species |
| reginula |
| Category |
| Tropicals |
| USDA Hardiness Zone |
| 10 |
| Canadian Hardiness Zone |
| Grow under glass |
| RHS Hardiness Zone |
| H1a |
| Temperature (°C) |
| 16 - 18 |
| Temperature (°F) |
| 60 - 65 |
| Height |
| 0.3 - 0.6 m |
| Spread |
| 0.5 m |
Photographs
Cultivars
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Description and Growing Information
Flowering Period
| General Description |
| Alocasia reginula is a small, herbaceous evergreen plant in the Araceae family with deep green to black peltate to obovate leaves. It has a bushy but compact growth habit, with leaves attached to pale green petioles with a whorled attachment at the base of its corm. It prefers high levels of humidity and part-shade for optimal growth to occur. |
| Landscape |
| It is primarily used as a specimen plant in a greenhouse but is also suitable as a houseplant due to its diminutive mature size. It can also be used in full shade planters along a patio in temperatures greater than 16 C, but will need to be taken inside or the corms stored during cold seasons. In 16 C or higher temperatures, it can also be used in full shade as a herbaceous border in gardens or mass plantings for a striking effect. |
| Cultivation |
| Alocasia reginula does best when placed in a location that receives part-sun to full shade (especially if outdoors), as its foliage can become bleached and burnt when exposed to too much direct sunlight. Additionally, it prefers temperatures between 16 C - 18 C. Another factor that greatly influences its health is humidity. This Alocasia prefers a range of 60% - 75% humidity but will tolerate as low as 40%. The excess moisture in the air allows new leaves to easily unfurl without it getting stuck and causing mechanical damage. Using a humidifier is a good way to supplement this for indoor specimens. In addition, Alocasia reginula thrives in a well-drained but moist growing medium, such as a combination of orchid bark, perlite, and cactus soil. If the medium is not well-draining or is watered too frequently, such as not letting the first few inches of soil dry out between waterings, it can be susceptible to root rot. It also prefers a neutral to acidic pH in the range of 5.5 - 7.0. To fertilize, a balanced fertilizer, such as 12-12-12, can be applied every 3 - 4 weeks during the growing season. Also, Alocasia reginula is prone to Tetranychus urticae (glasshouse red spider mite) and various mealybug species which harvest the sugars from the plants vascular system and cause mechanical damage. Despite being prone to pests, Alocasia reginula is relatively disease-free. Since this plant is generally used as a houseplant, in a greenhouse, or on an outdoor patio, it is not very urban tolerant and prefers a protected location. Finally, if Alocasia reginula becomes stressed as a result of any of the above requirements not being met, it can enter into dormancy and begin losing leaves to conserve energy. |
| Shape |
| The plant’s overall growth habit is bushy with peltate to obovate-shaped leaves and silver veins. As it ages from a corm into maturity, the plant’s shape remains the same, the only difference is the height and amount of leaves it possesses. It has fewer leaves when younger, and if cared for correctly, will have many when mature. |
| Growth |
| Medium |
| ID Characteristic |
| The first key identification characteristic of Alocasia reginula is the black foliage on the adaxial lamina which differentiates it from others within its genus. In addition, the prominent silver veins that can appear illuminated in bright light make this Alocasia distinct. The velvet to leathery texture of the leaves makes this plant very recognizable. |
| Pests |
| Alocasia reginula is prone to two major pests, glasshouse red spider mites and mealybugs. Tetranychus urticae, or glasshouse red spider mite, is very common in greenhouses but less so on outdoor plants. They attack the plant by sucking the sap from its vascular system and causing mottled damage to foliage. The mealybug species that can infest Alocasia reginula can include Pseudococcus longispinus, Pseudococcus calceolaria, and Planococcus citri. Mealybugs also suck the sap from the plants vascular system but they also produce honeydew and can cause sooty mold growth on the leaf and root surface. Mealybugs are a very common pest in greenhouses and can occur on outdoor plants, but it is seen with lesser frequency. Additionally, Alocasia reginula is relatively disease-free and not prone to being consumed by animals. Since it contains oxalate crystals throughout the plant, it irritates the esophagus and mouth when ingested. As a result, it is toxic to animals and unlikely to be eaten by them. |
| Habitat |
| Alocasia reginula is native to the warm and humid jungles of Borneo, Southeast Asia. It is an understory plant that receives the light filtered through larger plants above. It is found on limestone cliffs in dry and slightly acidic soil. |
| Bark/Stem Description |
| The petiole of Alocasia reginula is pale green in colour and semi-rigid to flexible. When mature, the petiole size is approximately 18 cm tall. When immature, the petiole can be as short as 1 cm. Corms of varying sizes are also present in Alocasia reginula below the soil surface. They grow from corms about 4 cm in diameter and produce tiny offshoot corms, less than 1 cm, from stolons beneath or at the soil surface. |
| Flower/Leaf Bud Description |
| As Alocasia reginula leaves and inflorescences prepare to emerge, they are protected by a cataphyll and prophyll. The cataphyll is light green and emerges from the base of the previous leaf’s petiole. It has a cylindrical appearance that narrows to a point at the tip and its size varies by plant maturity. On a mature plant, it is around 6.6 cm long when the cataphyll stops emerging. The prophyll is also light green and remains stationary on the lower portion of the previous leaf’s petiole. |
| Leaf Description |
| The leaves are simple and peltate to obovate. They have smooth margins, an acuminate apex, and asymmetrical auriculate base. The auriculate base is absent in immature plants. Additionally, on the adaxial lamina surface, it is deep green to black with silver venation and on the abaxial lamina surface, it is purple with green veins. When immature, the venation is thick and takes up most of the abaxial lamina space, with the remaining space being greener than the mature plant. The venation is divided into three major veins, from which primary venation occurs. The first vein, the anterior costa, runs down to the apex and the other two posterior costae connect to each of the posterior lobes. Pedate primary venation occurs from the posterior costae and pinnate primary venation occurs from the anterior costa. Furthermore, secondary venation occurs from the pedate and pinnate veins, as well as from the major costae, and are colocasiod. The leaf size varies by plant maturity, with an immature plant having around 4.5 cm long and 3.5 cm wide peltate leaves. As the plant reaches maturity, the leaves will be around 15 cm long and 8 - 11 cm wide. |
| Flower Description |
| The monoecious inflorescences of Alocasia reginula have little ornamental significance and are sporadic; they only occur on mature plants that receive optimal conditions during the growing season. The growing season can vary, if the plant is indoors and receiving consistent optimal conditions, then it will constantly be growing. In contrast, if it is outside, then the growing season would be considered spring and summer. The inflorescences are incomplete, as they are missing sepals and petals, and perfect, as they have both the stamen and pistil. Synflorescences will emerge from a cataphyll and prophyll and consists of a peduncle, spathe, and spadix. Both the prophyll, which is about half the length of the petiole, and cataphyll protect the inflorescence as anthesis begins to occur. The peduncle is the structure supporting the entire inflorescence. Additionally, the spathe, which is white with tiny purple spots, is about 5 cm in length. The lower part of the spathe is about 2.5 cm long and is “ovoid to subcylindric”. Also, the lower spathe ends at a loose constriction point where the upper portion begins. The upper spathe is about 2 cm long and is “broadly lanceolate”. Since it is a monoecious inflorescence, the erect, sessile, spadix is divided into male and female sections and totals about 4.5 cm long. The female portion is located beneath the constricted area and is about ¼ of the spadix length. It contains asymmetrically globose ivory coloured ovaries and each has a yellow, two-lobed stigma. Between the female and male organs, at the constriction zone, there is a sterile interval where dense synandrodia occur. Directly at to slightly below the constriction zone, the cylindrical male portion occurs, containing the white whorled synandrodia, and is about ½ the spadix length and half of its length in width. The white sterile appendix comprises the remaining part of the spadix, is “narrowly conic”, and is about ¼ of its length. In addition, the constricted area on the spathe may prevent accidental self-pollination by the pollen falling into its pistil. When female anthesis begins, the stigma is receptive to fertilization as soon as the spathe constriction releases. This allows pollinators to be lured to the pistils by an attractive scent produced in the lower spathe. Additionally, pollinators are unknown for Alocasia reginula and the Scabriuscula Group, however, Alocasia macrorrhizos are pollinated by flies from the Colocasiomyia genus. The flies are lured to the inner spathe in the morning by the attractive scent and eat, mate, and lay eggs there. The next day, the male anthesis begins and the flies leave for other inflorescences in female anthesis after making contact with the pollen. Next, the eggs hatch into larvae and pupate, leaving the inflorescence in adult form with the infructescence mature and fully intact. Thus, since Alocasia reginula inflorescences undergo anthesis the same way, it is probable that a species of fly or similar insect pollinates it the same way. Near the end of female anthesis, the spathe re-constricts and scent production stops. When male anthesis begins it involves the release of mealy pollen that easily falls and is collected into a lip between the spadix and limb. The rest of the spadix then rots off, leaving the female organs, after the anthesis has concluded. |
| Fruit Description |
| The simple infructescence isn’t documented or understood for Alocasia reginula besides its orange colour. Despite this, there is some knowledge on the genus’s fruits, which may also apply to Alocasia reginula. After the inflorescence is fertilized, the fleshy berries mature and the lower spathe increases in width to accommodate them. While the maturing and ripening occurs, the peduncle also increases in length. The capsule containing fleshy berries dehisces once ripe and has around “one to several” seeds in each. In addition to the seeds, the berry is also made up of a fleshy exocarp and mesocarp. Each berry is ovoid and has an approximate diameter of a few millimetres, and is analogous to one another. Overall, it is probable that Alocasia reginula has a similar fruit structure as most Alocasia have spathe and spadix inflorescences. Additionally, the other factor it likely differs in is fruit size, as it is a smaller species of the Alocasia genus and has a smaller inflorescence. |
| Colour Description |
| This Alocasia species’s traits remain year-round except for its inflorescence and fruit, which occur during spring to winter. It has an almost black appearance contrasted with silvery-white veins on its adaxial lamina. In contrast, on its abaxial lamina, it has purple colouring and light green veins. The petiole is also light green that is infrequently speckled with purple. Also, if it’s showing, the corm is light brown to white in colour. Its inflorescence has a white colour spathe flecked with purple spots and a yellow spadix that occurs during spring and summer. Finally, the infructescence is orange in colour and occurs from autumn to winter. |
| Texture Description |
| Alocasia reginula is of medium texture due to its succulent-like leathery leaves and smooth petiole. Its texture usually remains the same throughout all four seasons, however, texture increases during spring to early winter if it produces inflorescences and fruit. |
| Notable Specimens |
| An Alocasia reginula specimen can be viewed at the Chicago Botanical Garden in Glencoe, Illinois, The United States of America. |
| Propagation |
| Seed, offsets, and tissue culture are the three main propagation methods for Alocasia reginula. Seed: There is no specific documented information on how to pollinate Alocasia reginula, however, since all Alocasia have spadix and spathe inflorescences, they can be pollinated the same way. To grow from seed, first, the inflorescence must be pollinated, either by itself or a genetically unique plant’s pollen. If it isn’t found naturally pollinated, then manually pollinating is also an option. To do so, wait until male anthesis occurs and brush a cotton swab onto the sticky pistils, and then onto the pollen. Once the pollen is stuck to the cotton swab, gently brush it over all the pistils. The timing of male anthesis depends on temperature; the warmer the temperature, the faster it will occur. To access the pistils, a small piece of the spathe can be removed with sanitized secateurs. Next, wait until the infructescence matures, ripens, and dehisces to expose the orange fleshy berries. The time to mature and ripen also depends on the temperature. Once ripe, the seeds within the berries can be removed and soaked to decrease the germination inhibition chemicals. Distilled water must be used and it is recommended to soak for up to 24 hours. They should be planted right after soaking to ensure optimal germination rate and prevent drying out. Next, the seeds can be planted 0.6 cm deep into a moisture-retaining and airy media containing a mix of peat moss, pulverized perlite or vermiculite. The final step to planting is to store them in an environment that remains between 21 C - 29 C to ensure the correct temperature for germination. Additionally, the soil must remain moist and not dry out to prevent the death of the seedlings. There isn’t any documented germination period for Alocasia reginula, however, the length of time it takes for the radicle to emerge will vary based on its environmental conditions. After germination, the seedlings can be fertilized with a balanced fertilizer once cotyledons are present. Once they have their true leaves, they can be transplanted into pots about 2 - 5 cm diameter larger than their root zone and can receive the same care as mature plants. Offsets: Propagation by offsets can be done in spring or summer if outdoors or year-round if inside through the corms that they produce. First, remove the mother plant from its pot and gently loosen the soil around the root ball. The corms are typically nestled in the roots near the base of the mother plant’s corm and are globose in shape with a pointed tip. Next, take sanitized secateurs and prune the corm from the stolon attaching it. The corms can be planted with the tip oriented upwards in sphagnum moss in a warm, humid, protected, well-ventilated, and part-sun environment until they sprout. The temperature should remain around 16 C - 18 C with humidity at 60% minimum to ensure optimal sprouting conditions. Keep only the lower part of the corm covered in moistened moss to prevent rot. Once they grow secondary roots, they can be transplanted into a well-draining soil mix, such as orchid bark, cactus soil, and perlite. When transplanting, ensure all roots are covered in soil. Once leaves emerge, whether in sphagnum or soil, the corms can be watered with fertilizer. Continue to water and fertilize once every 2 - 3 weeks during the growing season. They can be planted outside once the danger of the last frost passes or can remain indoors as a houseplant. Tissue Culture: Tissue culture is a method commonly used in the commercialized production of Alocasia and is the most efficient method when compared to seed and offset propagation. There is no documented evidence on tissue culture propagation with Alocasia reginula specifically, but the key processes will remain the same for it as it has been successful with other Alocasia species. First, sprouted corms are removed from the mother plants and then washed for 30 minutes, running water should be used to prevent any residual soil particles from remaining on the corms. Next, the corms’ exterior needs to be treated with a solution of 3 drops of Tween 20 and 20% Clorox to sterilize them. Using distilled water that is sterile they are cleaned another three times before being sterilized with 3 drops of Tween 20 and 10% Clorox solution. Again, the corms are washed another three times with sterilized distilled water. Once the sterilization process has concluded, three corms are added to a glass 350 mL jar containing a type of agar-gel medium. Within the jar is a medium called Murashige & Skoog that contains essential macroelements and microelements, as well as amino acids, for tissue cultured plants. This medium must be autoclaved for up to 15 minutes at 121 C before use to ensure it is sterile. Further, a synthetic chemical called N6-benzyladenine may be added to this medium at an amount of 2.0 - 10.0 mg/L to stimulate cell division in the tissue cultured plants and increase propagation success. The inoculated corms should then be placed in a room receiving 21 C to 25 C temperatures and fluorescent lights emitting “32.5 g/mol/m2/s”. After approximately 4 weeks, the shoots that grew larger than 2 cm can be removed from inoculation. They should be cleaned with water from the tap and transplanted into a 1:1 ratio of sand and organic soil in trays. They can then be acclimatized in a full shade area within the greenhouse receiving 80 - 90% humidity and temperatures between 22 C and 30 C for another 4 weeks. After that period, they have been successfully acclimatized and can be planted outside in the garden beds or planters, or inside. Overall, despite there not being specific tissue culture propagation documentation for Alocasia reginula, the processes will likely also apply to it. |
| Ethnobotanical Uses (Disclaimer) |
| There are no specific ethnobotanical uses for Alocasia reginula, however, there are some for Alocasia macrorrhiza. Both Alocasia reginula and Alocasia macrorrhiza contain calcium oxalate crystals that irritate the mouth and lips if consumed raw. Despite this, Alocasia macrorrhiza corms are commonly eaten in India and Indonesia as it is high in starch and fibre. To decrease the toxicity, the corm must undergo washing, peeling, dicing, soaking overnight, blanching, and drying. Then, it is safe to eat and is commonly consumed alone, in mixed vegetables, and ground into flour or starch. Since Alocasia reginula also contains calcium oxalate, it can likely undergo the same processes to be eaten safely. It probably isn’t as frequently eaten as Alocasia macrorrhiza since it has a smaller corm. |
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