Giant taro

Giant taro: how do you recognise it?

Habit

Upright plant with a thick, green stem; indoors 1.5–2 m tall and up to 1.5 m wide.

Leaves

Large, arrow- to heart-shaped, glossy green with prominent veins; indoors often half a metre or more, much larger in the tropics. They stand at an angle on long stalks and turn towards the light.

Flower

Rare indoors: a typical arum flower, a spadix inside a pale yellow-green spathe.

Stem

Thick and fleshy; it stores water and reserves. Offsets appear at the base.

Sap

All parts contain sharp oxalate crystals that irritate the skin and mucous membranes.

Plants: March–May

Why grow it?

• Enormous, glossy leaves that instantly create a tropical atmosphere.
• Fast-growing: in a good season it produces a new leaf every few weeks.
• A striking specimen for a large, bright room, a conservatory or an office.
• It can go outside during a warm summer, as an eye-catcher on a sheltered patio.
• Easy to propagate from the offsets it forms at its base.

Giant taro: where does it grow best?

• Plenty of light, but no harsh midday sun: an east- or west-facing window, or 1–2 m from a south-facing one.
• Warm: 18–27 °C, never below 15 °C, and away from cold draughts.
• A humus-rich, open potting mix that holds moisture but drains well, acid to neutral.
• High humidity: group it with other plants or stand it on a tray of wet gravel.
• Allow a space about 1.5 m wide: the leaves reach far out.

Light

Bright, out of direct sun

Potting soil

Multi-purpose compost or airy, humus-rich compost

Acidity

Acid or neutral

Watering

Moderately or generously

Size

2 m tall, 1.5 m wide

Temperature

Minimum 15 °C

Goes well with

• Swiss cheese plant: Another large tropical foliage plant for the same bright, warm spot.
• Bird of paradise: Also large and exotic, with stiff, paddle-shaped leaves for contrast.
• Kentia palm: Fine, graceful fronds next to the large, entire leaves.
• Boston fern: Fills in the base and keeps the air around the plant more humid.

Giant taro: when and how to plant it?

Plant in March–May.

1. Repot in March–May, when new growth begins.
2. Choose a heavy, stable pot with a drainage hole, one size larger than the old one: the plant becomes top-heavy.
3. Use potting compost mixed with some bark or perlite, so that water does not sit in it.
4. Put a layer of clay pebbles or gravel in the bottom and set the plant at the same depth as before.
5. Firm lightly, water well and let the excess water drain away.
6. Wear gloves: the sap can irritate the skin.

Care

Watering

From April to September keep the compost lightly moist; let the top 2–3 cm dry out before watering again. Never leave water standing in the saucer.

Humidity

In dry air, mist the leaves with lukewarm water, or place a humidifier nearby.

Feeding

From April to September, a feed for green houseplants every two weeks; not in winter.

Leaves

Wipe the large leaves now and then with a damp cloth so that they catch enough light.

Turning

Give the pot a quarter turn every few weeks: the leaves grow towards the light.

Repotting

Every 1–2 years in spring, when the roots fill the pot.

Tip: If drops hang from the leaf tips in the morning, it has more than enough water: wait to water until the top layer of compost is dry.

Giant taro: when to prune it?

When: It is not pruned. Cut off yellowed or damaged leaves at any time of year.

How:

• An old leaf often turns yellow when a new one appears: that is normal. Cut it off once it is completely yellow.
• Cut the leaf stalk close to the stem with a clean, sharp knife.
• Trim brown edges with scissors, following the shape of the leaf.
• Wear gloves and wash your hands and the knife afterwards.

Caution: The sap irritates skin and eyes: do not rub your eyes while you work.

Pruning calendar and basic rules

Propagation

Offsets

When repotting in March–May, carefully pull or cut away offsets that have their own roots. Pot them in an open mix and keep them lightly moist and warm (20–25 °C).

Division

If there are several stems in the pot, divide the clump when repotting with a sharp knife, into pieces that each have their own roots.

Giant taro: how does it get through the winter?

• Not hardy: it stays indoors all year and should not drop below 15 °C.
• In winter it grows more slowly: water less, let the top layer dry out well and do not feed.
• Give it the brightest spot, away from cold windows, draughts and a hot radiator that dries the air.
• During a warm spell in summer it can go outside in a sheltered, partly shaded spot, as long as nights stay above 15 °C.

Diseases and pests

• Spider mite: Fine webbing and dull yellow speckling on the leaves, especially in dry, warm air. Shower the leaves and raise the humidity.
• Rot: Limp, yellow leaves and a soft, brown stem base caused by soggy compost. Let the compost dry out, cut away rotten parts and repot in fresh, open compost.
• Brown edges: Caused by dry air, draughts or irregular watering. Water more regularly and raise the humidity.
• Yellow leaves: One old leaf yellowing as a new one arrives is normal. If several yellow at once, it is too wet, too cold or too dark.

Through the year

• January: Little water, no feeding. Brightest spot, away from draughts.
• February: Watch for spider mite, encouraged by dry air from the heating.
• March: Repot if the roots fill the pot. Water a little more.
• April: Feed every two weeks. Remove offsets when repotting.
• May: Repot or pot up offsets. Dust the leaves.
• June: Fast growth: keep the compost lightly moist and feed every two weeks.
• July: In warm weather, possibly outside in a sheltered spot. Mist in dry air.
• August: Full growth. Give the pot a quarter turn regularly.
• September: Bring it in before nights drop below 15 °C. Last feed.
• October: Water less. Cut off yellowed leaves.
• November: Rest. Let the compost dry out between waterings.
• December: Rest. Away from cold windows and a hot radiator.

Edible and useful

Not edible. All parts of giant taro (alocasia) are poisonous: the sap is full of needle-shaped crystals (calcium oxalate) which, when chewed, cause burning pain and swelling of the mouth and throat, and it can irritate the skin and eyes. Despite the name it is not taro (Colocasia), whose corm is eaten after long cooking: never eat anything from your houseplant, as raw or undercooked it is dangerously acrid. The large leaves often hang at a child’s height: keep the pot out of reach of children, cats and dogs. Wear gloves when pruning and repotting, and wash your hands afterwards. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Did you know?

• When compost and air are moist, it pushes excess water out through the leaf tips; these drops are called guttation.
• In parts of Asia and the Pacific it has been grown for centuries as a food crop; the stem is only eaten after long cooking, because raw it is toxic.
• It belongs to the arum family, like the Swiss cheese plant, the anthurium and our native lords-and-ladies.