Swiss cheese vine

Identification and origin

Monstera adansonii belongs to the arum family, Araceae, which also includes calla lilies and elephant ears. It comes from the humid tropical forests of the Americas: it grows from Nicaragua and Costa Rica to Panama, across northern South America from Colombia and Venezuela to the Guianas, and south to Ecuador, Peru, Bolivia and much of Brazil, as well as Trinidad and the Lesser Antilles. It has naturalized in Puerto Rico.

It is an evergreen, herbaceous, climbing perennial: in the wild it clings to tree trunks with aerial roots and climbs toward the light of the canopy. Its glossy, heart-shaped leaves, medium to dark green, have oval holes between the main veins, which is why they are likened to Swiss cheese. In the wild a leaf can reach 18 in across; in a pot the leaves stay much smaller.

Indoors, with support, the plant reaches 3–8 ft tall and 12 in – 3 ft wide; without a stake it trails gracefully from a hanging basket. Outdoors in a tropical climate it grows to 10–13 ft. Growth is fast. The flower, a creamy white spathe around a yellowish spadix, appears in spring only on plants grown outdoors; indoors it is very rare.

It is often confused with Monstera deliciosa, a much larger plant with far wider leaves. The cultivar ‘Archipelago’ has variegated foliage, as does ‘Mint’; ‘Monkey Mask’ is another widespread selection.

Light

Give it bright but indirect light: near an east- or west-facing window, or at the back of a very bright room. Direct sun scorches the leaves.

A lack of light is easy to spot: new leaves come out smaller, with few holes or none, and the stems stretch out between leaves.

Watering

Let the mix become almost dry before watering: in practice, the top 1–2 in should feel dry to the touch. Then water thoroughly until water runs from the drainage hole, and empty the saucer: the pot should never sit in water for long. During active growth the plant uses a lot of water; in winter, water less often and less heavily.

If you can, use rainwater or filtered water at room temperature, especially if your tap water is hard. Overwatering is the most serious cause of decline: it rots the roots and can make the plant collapse.

This vine enjoys humid air. A humidifier, a tray of moist pebbles under the pot (with the pot base above the water) or grouping several plants together helps a great deal during the heating season. Wipe the leaves now and then to remove dust.

Potting mix

It needs an airy, free-draining, slightly acidic mix, with a pH of about 5 to 6. A good recipe is one part peat-free mix for acid-loving plants to two parts orchid mix. A peat-free, soil-based potting mix lightened with bark, perlite or a little charcoal also works. A mix that is too dense rots the roots.

During the growing season, from spring to late summer, apply a balanced liquid fertilizer once a month.

Temperature

The plant is happiest between 64 °F and 77 °F all year. Keep it away from cold air currents, but also from radiators, whose dry heat browns the leaf edges. Never let it drop below 50 °F.

It can spend the summer outdoors in its pot, out of direct sun, as long as nights stay mild. In the ground it can only be grown in USDA zones 10a to 12b.

Repotting

A young plant can stay in its original pot for a year or two, then be repotted every few years, in spring or early summer, or when roots fill the pot. Choose a container only slightly wider than the root ball, without oversizing.

At the same time, set a support in the center of the pot: a trellis, a stake or a moss pole. Keep the moss moist so the aerial roots can grip it. A climbing plant produces larger, more mature leaves with more holes than a trailing one.

Pruning

Pruning is not essential. If the plant outgrows its space, shorten the stems in spring; new shoots first carry smaller leaves with fewer holes while the plant settles. Wear gloves: the sap irritates skin.

Propagation

Stem cuttings are the easiest method, from spring to late summer. Take tip cuttings and stand them in a glass of water in a bright spot out of direct sun until they have formed a good set of roots, then pot them up like a young plant. Cuttings can also root directly in a small pot, ideally with gentle bottom heat, in summer.

Layering, including air layering, works well in fall: a stem is rooted while still attached to the mother plant before it is cut free. Seed is sown at 64–75 °F as soon as it is ripe, but it is very rare in cultivation.

Common problems

• Scorched leaves, dry pale patches: direct sun.
• Leaf edges turning brown: air that is too dry, most often near a heater.
• Few or no holes, stretched stems: not enough light, or a plant that is still young.
• Plant collapsing, soft stems at the base: root rot from overwatering or a poorly drained mix.
• Leaf spots: avoid wetting the foliage and keep air moving; rust, powdery mildew and leaf blight can also appear.
• Pests: spider mites, mealybugs and scale insects, aphids, whiteflies, thrips and fungus gnats. Scale and mealybugs leave a sticky residue and weaken the plant.

The same symptom can have several causes: check light, moisture in the root ball, temperature and roots together before acting.

Toxicity

The plant is toxic to people, dogs and cats if eaten, although severity is usually low. All parts, leaves, stems, roots, sap and flowers, contain calcium oxalate crystals. Chewing them causes inflammation of the mouth, throat and digestive tract, heavy drooling, vomiting and loss of appetite; the sap irritates skin and eyes. Wear gloves when handling it, keep it out of reach of children and pets, and if it is swallowed, contact a veterinarian or a poison control center.