Cast iron plant

Identification and origin

Aspidistra elatior belongs to the family Asparagaceae. Its native range is limited to southern Japan, where it grows in the forest understory; it has naturalized elsewhere, including southern China, Taiwan, Korea, Mexico, Spain and the southeastern United States. It reached Europe in the 19th century and became the darling of Victorian parlors, lobbies and barrooms because it survived where almost nothing else would, which earned it the names cast iron plant and bar-room plant.

It is a stemless evergreen perennial. Each leaf rises straight from the fleshy rhizome on a long petiole of 7–12 in; the lance-shaped, thick, glossy blade reaches about 2 ft long and 4–5 in wide, with parallel veins. The clump stands 12 in – 3 ft tall and widens very slowly: a young plant may make only two leaves a year. The flowers, small purple to brownish bells with eight lobes, open at soil level, hidden in the leaf litter, and rarely appear indoors. The genus name comes from the Greek aspidion, “small shield.” The cultivars ‘Variegata’ (leaves striped with creamy white) and ‘Milky Way’ (leaves dotted with white) are common.

Light

This is a shade plant. Bright, indirect light is ideal, but it will also settle for a dim corner or a north-facing window, growing more slowly there. Direct sun is its main enemy: it scorches and bleaches the leaves, which turn yellow, and a plant left in full sun eventually declines. Variegated forms carry a little less chlorophyll, so give them somewhat more light than all-green plants to keep good color. Flowering also requires more light.

Watering

Water when the mix has dried 2–3 in down, let the excess drain and empty the saucer: a cast iron plant hates sitting in water. From spring to fall, while it grows, water regularly; in winter the plant rests and needs much less. It tolerates dry spells, but watch the leaves: when it is short of water they lean to one side and turn pale, while a well-watered plant keeps deep green, upright leaves. Too much water leads to root and petiole rot.

Potting mix

A well-drained houseplant mix rich in organic matter that holds moisture without staying soggy. A slightly acidic to neutral pH (6 to 7) suits it. It tolerates poor soil but grows better in a fertile mix. In spring and summer an all-purpose houseplant fertilizer is enough; avoid fertilizers high in fluoride, to which it is somewhat sensitive. Variegated cultivars keep their stripes better in a moderately lean mix.

Temperature

It grows well between 59–86 °F and handles wide temperature swings without needing humid air. In winter, keep a potted plant indoors above 50 °F. In the garden it is grown in USDA zones 7a to 11b. The foliage is killed around 19 °F, but the crown resprouts; plants have reportedly survived down to -0 °F. Shelter it from winter winds, which burn the leaves.

Repotting

It grows so slowly that repotting is needed only at long intervals, once the clump has filled its pot. Do it in spring or early summer, while the plant is actively growing. A 8–12 in pot suits most clumps: rather than moving up in size again and again, divide the plant, or it will eventually become too heavy to lift.

Pruning

No real pruning is needed: cut damaged, yellowed or spotted leaves off at the base, one at a time. In the garden, old leaves marked by winter can be removed in late winter, before new ones emerge. Never remove more than about a third of the foliage at once, because the plant relies on its leaves to build reserves. Wipe the leaves now and then to remove dust.

Propagation

Divide the rhizome in spring or early summer. Pull the clump apart by hand rather than with a blade, keeping at least two or three leaves and healthy roots on each division, then pot them in fresh mix. Every node on the rhizome can produce a new shoot. It can also be grown from seed, but seed is rarely available.

Common problems

One symptom can have several causes: always check light, watering and temperature before treating.

• Bleached, yellow or scorched leaves: usually direct sun; cold or winter wind can also mark the foliage.
• Scale insects: small brown shields (females) and white flecks (males), mostly at the leaf bases and on the petioles.
• Spider mites: finely speckled leaves, yellowing and dying tips. Check leaf undersides; avoid horticultural oils, which leave mottled marks on the blade.
• Leaf spot: spots that start water-soaked, then turn tan to red-brown with a yellow halo, encouraged by foliage that stays wet. Remove affected leaves and water at the base.
• Root and crown rot: leaves that yellow and come loose at the base, black roots; the mix is too wet or poorly drained.
• Slugs and snails: holes in the leaves of plants grown outdoors.
• Fading stripes: mix too rich for a variegated cultivar.

Toxicity

No toxicity reported: the cast iron plant is listed as non-toxic to dogs, cats and horses and is not known to be harmful to people.