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. Also, it prefers high levels of
humidity and part-shade for optimal growth to occur. |
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. Also, the velvet to leathery texture of the leaves makes this plant very
recognizable. |
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. |
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. |
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 and humidity at
60% minimum to ensure optimal sprouting conditions. Keep only the
lower ? - ? 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 & Skoorg 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 ?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. Then
they can 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. |
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 plant’s
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. |
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
calceolariae, and Planococcus citri. Mealybugs also suck the sap from
the plant’s vascular system but they also produce honeydew and can cause sooty
mould growth on the leaf and root surface. Also, 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. |
Notable Specimens | An Alocasia reginula specimen can be viewed at the Chicago Botanical Garden
in Glencoe, Illinois, The United States of America |
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. Also, 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 ? 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 ? 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 ? 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’
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. Also, 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’ 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. |