Plant Parenting: Growing aroids and other epiphytes

SINGAPORE – In July’s Plant Parenting column, we learnt about orchids and other epiphytic plants, which grow on the surfaces of plants or objects. This month, explore hemi-epiphyte plants, which spend part of their lives rooted in the ground.

They can be classified into primary or secondary hemi-epiphytes.

Aroids are members of the Arum family (Araceae) and many species are secondary hemi-epiphytes. They start out growing in the ground and, later in life, grow as epiphytes on trees.

Plants from the genera Philodendron, Monstera, Epipremnum, Rhaphidophora, Syngonium and Anthurium, with their distinctive foliage, are popular aroids often grown in high-rise and outdoor gardens.

In retail nurseries, hemi-epiphytic aroids sold as potted plants appear as an attractive cluster of leaves. With time, plants adopt a vining habit. Those with thinner stems develop a trailing habit with cascading stems.

In many species with such a growth habit, leaves become smaller with time. Plants may also produce leafless stems. 

A closer look at the stems of hemi-epiphytic aroids will reveal small, stubby nodes along the stem. Roots are produced from each node and take up nutrients and water.

In natural surroundings, the roots will first grow into the moist, aerated leaf litter layer on the forest floor until the stem finds a tree to grow on. They then grow upwards along the tree trunk as the plant climbs towards a light source. In very humid environments, you can sometimes see long aerial roots growing from the stems of climbing plants.

Depending on the species, tree bark can have a porous structure that retains some moisture. This allows the roots of hemi-epiphytic aroids to grow into the bark, so the plant can anchor itself to its host.

For some aroid species, their leaf shape will increase in size as they grow. In the plant’s adult stage, leaves develop holes or perforations, taking on a “dissected” look, via a process called fenestration. This is thought to improve air flow, reducing wind resistance and damage to plants growing high above the canopy of trees.

High-rise gardeners who grow aroids in containers typically provide a vertical pole for their plants to climb. The traditional version is the coconut coir pole, which consists of coconut husk fibres wrapped around a plastic pipe. These poles are available in various fixed lengths at nurseries.

A gardener can also build his or her own climbing pole by using wire mesh that is rolled into a cylinder and stuffed with organic material, such as coconut husk fibre or sphagnum moss. Newer pole designs, which can be found for sale online, take the form of short perforated plastic cylinders that can be connected to lengthen the support as the plant grows. 

The disadvantage of using an organic material is that it will break down over time. Some gardeners overcome this limitation by wrapping a plastic pipe with geotextile cloth (a non-biodegradable material) or a dense plastic shade net to make the pole more durable.

The pole also needs to be weighed down or secured to the base of the pot. As the plant grows, it will get “top-heavy” and can topple over. Both the pole and pot should be made of durable materials. 

To encourage your aroids to climb, place the stem of the plant near the support and tie it to the pole. For roots to grow into the support, you need to keep the material moist via regular misting.

As the plant grows, its stem will thicken. Cut any twine that was used to bind the stem to the support, doing so carefully to avoid injuring the plant. 

In gardens where sunlight comes from only one direction, avoid rotating the pot once your plant has started climbing. This will preserve the orderly arrangement of the leaves as the plant grows.   

For those with outdoor gardens, hemi-epiphytic aroids can be trained to climb onto a wall, tree or palm. However, this can make inspection of that surface difficult, as the plant’s leaves and stems will obstruct one’s view.   

This approach to growing hemi-epiphytic aroids can be adapted for non-aroids with a similar growth habit. Examples include Dragonfruit (Selenicereus), Pepper plant (Piper nigrum) and Climbing Fig (Ficus pumila).