Alocasia macrorrhizos holds enormous arrow-shaped leaves upright on thick stems, pointing at the ceiling rather than outward. A mature indoor plant reaches around 1.8m (6ft).
It is a hungrier, thirstier and faster plant than most Alocasia, and easier for it. It has more capacity to recover from mistakes.
Light
Alocasia macrorrhizos grows best in bright, indirect light, and it takes more of it than most of the genus. A couple of hours of direct morning sun is fine.
Too little light
The stems stretch and lean, and the leaves come in smaller. A plant this size needs real light to support the leaves it makes.
Too much light
Hot afternoon sun bleaches and scorches the leaf surface.
Watering
Water when the top 3-5cm (1-2 inches) of soil is dry. It drinks considerably more than a smaller Alocasia, because those leaves lose a lot of water.
On average:
- Spring & summer: twice a week
- Autumn & winter: once a week
Signs of overwatering
- Leaves yellow from the oldest inward
- Stems soften at soil level
- Soil stays wet for days
Signs of underwatering
- Whole leaves droop and the stems bend
- Leaf edges go crisp
Guttation is normal
Large droplets of water on the leaf tips in the morning are not a problem. The plant is shedding excess water through its leaves, which is common in well-watered Alocasia and a sign of a healthy root system.
Humidity and temperature
Humidity above 60% keeps the large leaves in good condition. Below that the edges go crisp, and there is a lot of edge on a leaf this size.
Keep it between 18°C and 29°C (65-84°F). Below 15°C (59°F) it goes dormant.
Soil and repotting
Soil
A chunky, free-draining aroid mix of bark, perlite and coco coir.
Repotting
Every year in spring while it is growing fast. Use a heavy pot, because a mature plant is genuinely top-heavy and a plastic pot tips over.
Feeding
Balanced liquid fertiliser every 2 to 3 weeks through spring and summer. This is a heavy feeder by houseplant standards, and it will grow noticeably faster for it.
Stop completely in autumn and winter.
Pruning and grooming
Remove leaves at the base once they yellow fully. Each leaf is large and the plant sheds older ones as it produces new growth, so some loss is normal.
Wipe the leaves. They are big enough that dust makes a visible difference.
Dormancy
Like all Alocasia, it can drop everything and retreat to the base in low light or cold. Keep the soil barely damp, stop feeding, and wait.
Firm growth below the soil means it is alive. Soft and hollow means it is not.
Common problems
Drooping leaves and bending stems
Usually thirst. A plant this size wilts fast and recovers within hours.
Yellowing lower leaves
Normal in small numbers. Several at once means overwatering.
Crispy brown edges
Humidity too low.
Water droplets on leaf tips
Guttation. Normal and harmless.