How to grow alocasias

Why grow alocasias?

Alocasias are spectacular plants, ideal for creating a jungle look in your home. They usually have large, glossy, shield-shaped or pointed leaves with prominent veins. Alocasias originate in tropical forests, where they evolved extra-large foliage to catch the maximum amount of sunlight coming through the tree canopy overhead.

They like warm, humid conditions, in bright but not direct light. In summer, alocasias can be very fast growing, often producing leaves on a weekly basis. In winter, they need a period of dormancy

Dormancy refers to a period of inactivity in plants, during which they slow down or stop their growth, conserving energy and resources. This is a natural process that helps them survive harsh conditions, such as winter or drought. Dormancy in seeds is a mechanism that prevents them germinating until environmental conditions are favourable for growth.

, in cooler, drier conditions.

Alocasias are often known as elephant’s ear, due to their large leaves. They’re closely related to taro (Colocasia esculenta), a widely grown root crop in Africa and South-East Asia. Despite this, alocasias contain toxic compounds, so should not be eaten, and it’s best to wear gloves when handling them. Alocasias are in the arum family (Araceae), along with other popular houseplants such as the peace lily (Spathiphyllum) and Swiss cheese plant (Monstera deliciosa), and like similar growing conditions. See our guide to amazing arums.

Choosing alocasias

There’s a wide range of alocasias to choose from, with leaves of different shapes, sizes and colours. Some can grow very large, such as Alocasia macrorrhizos andA. odora, which can reach 1.5m (5ft) tall, creating a fabulous jungle effect, while others are more compact, ideal for a small bathroom or other similarly warm, humid spot.

Popular choices include:

• Alocasia x amazonica ‘Polly’ – one of the most widely available, with striking dark-green, silver-veined leaves
• A. ‘Stingray’ – has leaves shaped like its sea-dwelling namesake
• A. ‘Sarian’ – with upright, boldly veined, arrow-shaped foliage
• A. lauterbachiana – has long, spear-shaped, wavy-edged leaves

A. amazonicahas an RHS Award of Garden Merit, showing it performed well in growing trials, so makes a reliable choice.

Choosing the best houseplants

Buying alocasias

Alocasias are usually available in garden centres and other houseplant retailers. For the widest choice, try online houseplant specialists.

When buying in person, choose healthy-looking plants with unblemished leaves and no signs of wilting or insect damage. As these are tropical plants, take care to keep them warm when transporting them, as low temperatures can damage or even kill them.

Buying: garden centre plants

Buying: mail order plants

Alocasia can usually be left in their original pot for a year or so, but should then be repotted every couple of years, especially the faster-growing species. Check for overcrowded roots and repot in spring if necessary.

When repotting, choose a peat-free houseplant compost

Can refer to either home-made garden compost or seed/potting compost:

• Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own.

, or a peat-free multi-purpose compost and add horticultural grit to improve the drainage – about three parts compost and one part grit.

Choose a pot that’s only about 5cm (2in) in diameter larger each time, to avoid overpotting problems. Position the plant in the new pot so the top of the rootball

The roots and accompanying soil when a plant is removed from a container or lifted from the ground.

is just below the surface of the compost. Larger alocasias are best planted in a heavy terracotta pot, to give them more stability.

It’s best to wear gloves when handling alocasias, as the sap

Sap is a fluid that circulates through a plant's vascular system, in a similar way to blood moving through our veins. Phloem sap carries the sugars produced in the leaves by photosynthesis down to roots and other storage organs, as well as carrying minerals and hormones. Xylem sap is watery and transports nutrients absorbed by the roots upwards to the rest of the plant. Some plants leak sap from wounds or pruning cuts, and this is known as bleeding.

can be an irritant.

See our guides on repotting houseplants:

How to repot a plant

Location

Alocasias grow best in bright but indirect light. Strong sunlight can scorch the foliage. While they can survive in lower light, their growth will be much slower.

Artificial lighting for indoor plants

Temperature

These tropical plants should be kept warm, above 16°C (60°F) throughout the growing season

The period of time when an individual plant is in active growth. This will depend on the local climate and light levels, and can vary between different plants, although it is broadly from spring to autumn.

, from spring to autumn. Also keep them out of cold draughts.

In winter, give them cooler and drier conditions, but still above 10°C (50°F), to allow them to go dormant. They may lose some of their foliage during this time, but this is nothing to worry about. They’ll produce plenty of fresh leaves once they come back into growth in spring.

Watering

Water as needed from April to October, once the top 5cm (2in) of compost

Can refer to either home-made garden compost or seed/potting compost:

• Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own.

has become dry. Turn the plant round slightly at each watering to prevent it leaning towards the light and becoming lopsided and unstable.

If the compost begins to dry out very fast after watering, it’s usually a sign the plant is pot-bound

Describes a pot-grown plant whose roots are filling the container, densely packed and intertwined. Check the roots of container plants regularly, and re-pot into a larger container before they become pot-bound, to ensure continued healthy growth. The roots of pot-bound plants are unlikely to spread out into new soil or compost without first being physically loosened.

and needs to be moved into a larger container – see Planting, above.

During winter, when the plant goes dormant, reduce watering to a minimum. Overwatering, especially while dormant, can cause the roots to rot.

Houseplants: holiday care

Humidity

Alocasias like medium to high humidity

The concentration of water vapour in the atmosphere. This affects the rate at which plants transpire (lose water from their leaf pores), which in turn affects how much water their roots absorb from the soil. If air humidity is low, plants transpire quickly and become at risk of wilting if water is lost from the leaves faster than it can be absorbed by the roots. Different plants require different levels of humidity to thrive. Many tropical houseplants need high humidity and are best grown in a steamy bathroom, misted regularly or placed on a saucer of damp pebbles. In a greenhouse, humidity can be raised in hot weather by damping down (wetting) the floor or overhead misting.

through the growing season, but the air in our homes is often very dry. Try some of the following to keep your alocasia happy:

• stand the pot in a tray of gravel or clay granules, then add water to just below the surface of the gravel, and top up regularly as it evaporates
• position the plant in a bathroom
• mist the leaves
• group several plants together
• use a humidifier

Feeding

To fuel the production of large leaves, feed with a general liquid fertiliser during the growing season, from April to October, following the dose rate and frequency recommended on the packaging.

Fertilisers

No pruning or training is required, other than removing fading or dead leaves, cutting them off at the base. Always wear gloves when handling the leaves, as the sap

Sap is a fluid that circulates through a plant's vascular system, in a similar way to blood moving through our veins. Phloem sap carries the sugars produced in the leaves by photosynthesis down to roots and other storage organs, as well as carrying minerals and hormones. Xylem sap is watery and transports nutrients absorbed by the roots upwards to the rest of the plant. Some plants leak sap from wounds or pruning cuts, and this is known as bleeding.

can be an irritant.

The easiest way to propagate an alocasia is by separating and potting up any offsets that form in spring. These are new small plants that sprout around the base of mature plants. Carefully slice down with a knife, separating it from the mother plant and taking as much root as possible, then pot up individually in gritty, peat-free compost

Can refer to either home-made garden compost or seed/potting compost:

• Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own.

.

Alternatively, you can divide the fleshy rhizome in late spring/early summer and pot up the pieces. Keep them in warmth and good light and they’ll soon produce new shoots.

Take care when handling alocasias, as the sap

Sap is a fluid that circulates through a plant's vascular system, in a similar way to blood moving through our veins. Phloem sap carries the sugars produced in the leaves by photosynthesis down to roots and other storage organs, as well as carrying minerals and hormones. Xylem sap is watery and transports nutrients absorbed by the roots upwards to the rest of the plant. Some plants leak sap from wounds or pruning cuts, and this is known as bleeding.

can irritate skin and the plants contain toxic compounds.

If you give alocasias the warmth, humidity

The concentration of water vapour in the atmosphere. This affects the rate at which plants transpire (lose water from their leaf pores), which in turn affects how much water their roots absorb from the soil. If air humidity is low, plants transpire quickly and become at risk of wilting if water is lost from the leaves faster than it can be absorbed by the roots. Different plants require different levels of humidity to thrive. Many tropical houseplants need high humidity and are best grown in a steamy bathroom, misted regularly or placed on a saucer of damp pebbles. In a greenhouse, humidity can be raised in hot weather by damping down (wetting) the floor or overhead misting.

, water and nutrients

To grow well, plants need a wide range of nutrients in various amounts, depending on the individual plant and its stage of growth. The three key nutrients usually taken up from the soil are nitrogen, phosphorus and potassium. Plants also need carbon, oxygen and hydrogen to make carbohydrates — their main energy source. Carbon and oxygen come from the air as carbon dioxide, while hydrogen is drawn from water absorbed by the roots. Other important soil nutrients include magnesium, calcium and sulphur. Most garden soils contain enough of these nutrients to support healthy plant growth.

they need through the growing season

The period of time when an individual plant is in active growth. This will depend on the local climate and light levels, and can vary between different plants, although it is broadly from spring to autumn.

, followed by a cooler, drier period over winter, they are usually vigorous, robust plants. Try to avoid the following:

• Low humidity – this can cause browning on the leaf edges and may attract red spider mites, which thrive in a dry atmosphere
• Watering too much in winter – or overwatering in general – can lead to root rot
• Cold draughts, particularly in winter, can be damaging
• Low temperatures – keep alocasias above 10°C (50°F) at all times, and during the growing season they need at least 16°C (60°F)

How to help a poorly houseplant

Leaf damage on houseplants