Alocasia infernalis 'Black Magic'. Copyright: Pinterest.
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Your Alocasia infernalis is best situated in a bright location that boasts overhead light, but if you can't provide this, within two metres of a window will still do the job - albeit slower growth. Those situated in a shadier location must have their leaves rinsed from time to time to improve the light-capturing efficiency. Never allow it to sit in strong sunlight for more than three hours a day, as too much light will result in a pale, washed-out appearance with possible brown patches.
If it were up to us, we would locate our plant on a windowsill. A north, east, or west-facing window is fantastic for good quality growth, or under a grow-light for optimum growth.
Allow the top third of the soil dry out in between waters during the active growth period, reducing this further in the autumn and winter. Due to the sensitivity of their root systems, never apply cold water as it may weaken its health and well-being over time. For those that use tap water (instead of rainwater or fresh bottled water), allow it to stand for at least 24hrs to settle the high levels of chloride and fluoride found from the tap. Under-watering symptoms include wilting, little to no growth and greying leaves - these issues are commonly down to too much light/heat, or forgetfulness. Alternatively, over-watering symptoms include rapidly yellowing lower leaves, wilting (root rot), brown spots on leaves, and a rotten stem. Specimens that are located in a darker area are more likely to adopt root rot as the soil may not dry out sufficiently in between waters. Remember - under-watering is far better than over-doing it, due to the species' base that can retain moisture in times of short-lived droughts.
Average room humidity will be accepted by an Alocasia, but remember to introduce a pebble tray while the heaters are operating to counteract dry air. A quick monthly hose down in the shower will hydrate the leaves, eliminate dust particles and help reduce numbers of pests, most notably Spider Mites.
Fertilise every four waters during the growing period before reducing this to every six in the autumn & winter. Although an ‘All-Purpose' fertiliser will still do the job, we'd recommend using a specific 'Houseplant' labelled fertiliser as it'll support the vital thirteen nutrients that this species will need to grow.
The rapid yellowing of older leaves and a wobbly plant are a clear sign of over-watering, usually caused by too little light. Although Alocasia can do well in darker locations, the frequency of irrigations must be reduced to counteract the chance of root rot. People don't realise that a plant's root system needs access to oxygen too; when soil is watered, the air will travel upwards and out of the potting mix. A lack of accessible oxygen for the roots will cause them to subsequently breakdown over the oncoming days. Click on this link to learn more about root rot and how to address it, and always feel the pot's weight for confirmation (heaviness = good soil moisture, & vice versa).
An array of simultaneous cultivation issues will increase the chance of developing yellowed leaf-sections with browned halos. Firstly, the location may be too dark, with its compost staying too saturated in-between waters; if mould is growing across the soil, this is usually a bad sign. Further, you're potentially using too cold water or tap water that hasn't been allowed to sit for 24hrs. This period of rest will not only bunk-up its temperature, but the harsh chemicals used to preserve water hygiene (fluoride & chloride) will begin to settle after a few hours. If possible, use fresh bottled water from a shop or supermarket to prevent further chemical burns. The final culprit might be lack of fertilisation, with regular feeds being paramount for long-lasting, healthy leaves. If the specimen hasn't been nourished in over two months, it'll begin to show signs of nutrient deficiencies seen in this article.
If this common problem has occurred with your specimen, remove the affected leaves (not areas) and improve the growing conditions considerably. Fertilise regularly with lukewarm water and be sure to allow the top third to dry out in between hydrations.
If your specimen develops basal collapse, it may spell the end of its life. The rhizomes, which are located below the soil line and act like a modified stem, are the lifeline for a successful specimen, so any issues of rot will kill it outright. If yours has problems with this, be sure to take the plant out of the pot and inspect its roots and base. Prune away any rotten areas and check its base for a softened profile. Remove any individual plants that have a rotten bottom and repot the healthy specimens in a fresh batch of 'Houseplant' compost. Provide a brighter location and reduce the number of waters slightly to avoid further rot. Discard the plant if there is no sign of health below the soil line, especially if its base is mushy and hollow.
Regular waters and fertilisations are essential. Periods of droughts will quickly slip the Alocasia back into its dormancy period, thus causing stunted growth and a bewildered plant owner. If it hasn't repotted in a while, there may be too many roots and not enough soil to retain moisture, thus leaving the compost to dry out quicker. Click on this link to learn more about a transplant.
Pests could arise at any time, with infestations starting from the original nursery or via contamination in your home. Spider Mites and Mealybugs to tend to be the usual inhabitants, with the first being minute and almost transparent, roaming the leaves in search of chlorophyll and a site to hide its eggs. The latter, however, will stand out much more, with white cottony webs developing across the foliage and stems. Thoroughly check the plant's cubbyholes before giving it the all-clear, or click on the appropriate links to learn more about eradicating these issues!
Too low humidity can cause excessive browning tips with yellow halos. Although this won't kill your specimen, you may want to increase the local moisture to prevent the new growth from adopting these symptoms. Mist or rinse the foliage from time to time and create a humidity tray while the heaters are active to create a stable environment. Browning leaf tips are an inevitable part of a leaf's maturity though, so never be too disheartened if your specimen is showing signs of this!
Clean the leaves regularly. Although this isn't too much of an issue, a build-up of dust particles can clog up the plant's pores, causing lowered light capturing-efficiency. Rinse the topsides of the leaves down once a month to keep levels down and improve growing conditions.
Mould or mushrooms developing on the soil means two things - too little light and over-watering. Despite the harmlessness, it'll prove unsightly to most gardeners and is therefore removed once known. To remove, replace the top two inches of the soil for a fresh batch of 'Houseplant' compost. Either increase the amount of light received (no direct sunlight for the first few weeks to prevent environmental shock) or decrease the frequency of waters slightly. If the mould is accompanied by yellowing lower leaves, you may also have a case of root rot.
Other yellowing leaves - it isn't easy to accurately pinpoint why this is happening as it could be due to many different reasons. If the lower leaves are yellowing in quick concession, it could be over-watering. Do not allow the soil to become soggy or waterlogged; failure to do so will cause root rot and possible death. For severe cases, take the plant out of rot pot to examine for root rot - a transplant may have to be performed. The second reason why its leaves are yellowing could be due to either too much sunlight or not enough water. As mentioned above, under-watering can cause an Alocasia to slip into its dormancy period. Still, persistent droughts with direct sunlight will cause further damage in the likes of yellowing leaves, stunted growth and wilting.
Alocasia infernal was documented by Peter Charles Boyce in the late 20th century, who used the Latin word for 'hellish', in reference to the warm tone of its foliage. The species has natural distributions across the island of Borneo, where it mostly occurs between the valleys of wetland forests.
10° - 30°C (50° - 86°F)
H1b (Hardiness Zone 12) - can be grown outdoors during the summer in a sheltered location with temperatures above 12℃ (54℉), but is fine to remain indoors, too. If you decide to bring this plant outdoors, don't allow it to endure any direct sunlight as it may result in sun-scorch and dehydration. Regularly keep an eye out for pests, especially when re-introducing it back indoors.
Over 0.6m in height and 0.4m in width once the specimen reaches maturity. The ultimate height will take between 5 - 8 years to achieve, with several new leaves grown per year.
Remove yellow or dying leaves, and plant debris to encourage better-growing conditions. While pruning, always use clean utensils or shears to reduce the chance of bacterial and fungal diseases. Never cut through yellowed tissue as this may cause further damage in the likes of diseases or bacterial infections. Remember to make clean incisions as too-damaged wounds may shock the plant, causing weakened growth and a decline in health.
Via Seed or Basal Offset Division (attached to the lower stem).
Basal Offset Division (Easy to Moderate) - Your plant will produce several offsets that can be separated once they have a sufficient root system, with the stem surpassing 6cm in height. If possible, water the soil 24hrs before the main event to reduce the risk of transplant shock, when its dry root systems are over-fingered. Take the plant out of its pot and place your fingers close to the nodal junction - soil may have to be removed for better access. Push the chosen offset downwards until you hear a snap. Separate the foliage and its root system away from the mother plant, mentally noting the high risk of damage. Transplant in the appropriate sized pot with a fresh batch of 'Houseplant' soil. Maintain evenly moist soil and situate it in a bright, indirect location away from any direct sunlight. After eight weeks, treat it like a normal specimen following the care tips above!
As this species is part of the Araceæ family, their inflorescences aren't showy. Much like a Peace Lily's flower, their flowers consist of a white or green spathe (the spoon-like shell) with the spadix being the site of pollination. Blooms can last up to three days and are usually visible during late spring or early summer around 30cm+ from the soil line.
In some cases, a show of flowers may indicate the plant is stressed; common causes of this are irregular waters, root rot and environmental shock.
Repot every two or three years in the spring, using a 'Houseplant' labelled potting mix and the next sized pot with adequate drainage. Alocasia are far better at being potbound for several years due to the heightened risk of root rot and repotting-issues (like transplant shock, which will result in yellowed leaves and wilting), so only repot if you feel it's wholly necessary.
Hydrate the plant 24hrs before tinkering with the roots to prevent the risk of transplant shock. For those situated in a darker location, introduce an extra amount of perlite and grit into the new soil to downplay over-watering risks. Click on this link for a detailed step-by-step guide on transplantation, or via this link to learn about repotting with root rot.
Book a 1-to-1 video call with Joe Bagley if you'd like a personal guide to repotting your houseplant. This will include recommending the right branded-compost and pot size, followed by a live video call whilst you transplant the specimen for step-by-step guidance and answer any further questions!
Keep an eye out for mealybugs, spider mites, thrips & fungus gnats that'll locate themselves in the cubbyholes and undersides of the leaves. Common diseases associated with this species are root rot, leaf-spot disease, botrytis, rust, powdery mildew & southern blight - click here to learn more about these issues.
This plant is classified as poisonous due to varying concentrations of calcium oxalate crystals found around the plant's body. If parts of the plants are eaten, vomiting, nausea and a loss of appetite could occur. Consumption of large quantities must be dealt with quickly; acquire medical assistance for further information.
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