Plant Health: A High-rise Container Gardener’s Journey

My journey as a high-rise container gardener started about eight years ago. It was a thoroughly unremarkable beginning: after buying two adorable potted ivy and arrowhead plants from the nursery to ‘beautify’ our apartment, we (the wife and I) discovered to our horror that watering our new ‘acquisitions’ would cause water and soil material to drip out from the base of their pots!

Unwilling to damage furniture, wet flooring or risk dengue spread by placing a tray beneath the pots, we opted to position the plants outside our apartment along the common corridor (where we noticed most of our neighbours did the same). In a curious way, the first two plants we affectionately named “Jimmy” (the arrowhead) and “Albert” (the ivy), seemed to grow on us.

A foray into the world of plant keeping with (L to R): Albert, Jimmy, Scindy, Dracki and Tom.
Photograph by: Samuel Eio

The original Jimmy is no longer there today, but I have Jimmy’s great-great-grandson sitting in my office, right above my workstation. (Fun fact: he has travelled with me to four previous workplaces!) Sadly, Albert did not survive after we gave him away to a relative. Yet from these two plants, our lives have been positively changed in many ways. Something happens when keeping plants, or rather when plants are keeping you.

Over-watering

Shortly after starting with two plants in the corridor, I ventured to purchase a few more ornamentals and some herbs from the nursery: sweet basil, mint and thyme. Thus, I divided my little container garden into non-edibles and edibles. Around the same time, I bought a small planter tray which could be clamped to the corridor ledge so that the herbs received more sunlight. The edibles proved more challenging to upkeep. I didn’t really have much success with thyme – my guess is that I must have over-watered it due to inexperience. The other two, basil and mint, simply flourished with the corridor’s sunlight and my (over?) generous watering – or so it seemed.

Pests, plant diseases

A little later, I noticed some sticky black streaks starting to form at the basil’s stem. Initially (and being a total noob), I thought nothing of it. Little did I know, I was paying the price for my over-zealous watering. Some brown-grey patches appeared on the leaves, withering them! I still am unsure what exactly ‘blasted’ the basil, but some fungus or mildew was likely the culprit. A knowledgeable neighbour (Thanks, Uncle!) taught me to water the roots only, not overhead. The attack on the mint was more subtle – its leaves would appear unnaturally curved or curled with yellowish patches, and the entire plant would look dry and under-watered, despite being regularly-watered. Boom! That was when I got my crash course in disease management in plants. It dawned on me that plant health was part of the whole gardening experience.

Aphids

The tormentors of my plant – aphids – come in a few different species of winged and wingless pests. A quick search online will tell you that they have rather complicated life cycles, starting “life as eggs, laid on the host plant or on other plants. The eggs hatch into immature females, called nymphs, which shed their skins as they outgrow them, finally becoming wingless adults. They are viviparous, producing living young, which in time produce more young. Finally, winged females are produced which can migrate to other plants and lay eggs there.” Okay, that made sense; now I know how these creatures got onto my healthy plant.

Close up ‘post-mortem’ of a cactus with aphid cast skins.
Photographs by: Samuel Eio

“Aphids feed by sucking the sap of plants, usually attacking young shoots and leaves.” Check. Choice, tender parts – opportunistic pests.

“Some aphids cause extreme leaf curling. Some cause distortion of shoots, stems and flowers. Some cause galls and swellings. Some infest roots.” Ugh. How disgusting. I hate aphids.

“Aphids also open wounds which may allow certain diseases to attack. Aphids excrete honey which attracts sooty moulds and these weaken and disfigure plants.” Double-check. Now I know what is going on. However, the plot thickens.

“Also, certain virus diseases are spread by aphids feeding on diseased plants and then carrying virus-infected sap to healthy plants. As aphids are a serious pest, they must be controlled.” Yes, I agree. But how? That particular source then went on to list a whole bunch of chemicals “suitable for the amateur” like dimethoate, formothion, rotenone just to name a few – which I had absolutely no experience with!

The thought of myself eating leaves which had been sprayed with weird chemicals (however diluted) made me feel very uneasy. As I contemplated abandoning my afflicted plants at the void deck, I resisted the urge to actually do so, telling myself that that was not the way as a responsible plant owner. I was determined to find a better solution to deal with the aphids.

Mealybugs

As if the aphid attack was not bad enough, things simply have a way of getting worse. A new enemy – soft-bodied and wingless, appeared as an insidious white cottony mass on the underside of the leaves and young stems.

“Mealybugs,” says Ian Walls, “are particularly difficult to control “because of their waxy impervious covering, and because of their habit of gathering inside curled leaves…and in other hiding places.” In my own experience, I have seen mealybugs attack plant stems and even on shallower roots. Both young and adult mealybugs feed by sucking plant sap from long mouthparts called stylets (think miniature drinking straws) and weakening the plants by depriving them of sap.

Mealybugs also excrete a sweet sticky substance called honeydew, that some species of ant find irresistible and ‘milk’ them for more of the liquid. Honeydew, in turn, attracts unsightly black moulds (known as ‘sooty moulds’) to grow on the plants, interfering the plant’s healthy growth. 

Mealybug infestation on a hibiscus plant, a challenge for any plant enthusiast.
Photograph by: Samuel Eio

The solution to mealybugs’ infestation? Apparently, alcohol is one of them. Dipping cotton-buds in rubbing alcohol and dabbing it on these critters is suggested; otherwise, there is the hassle-free option to prune out light infestations. Another control measure is to introduce natural predators like ladybugs and lacewings and the famed Mealybug Destroyer (Cryptolaemus montrouzieri). 

Other control measures include using a stream of pressurised water to hose off the pests, or regularly washing leaves with a leaf shine emulsion made from neem oil. I experimented with cooking oil or olive oil mixed with dishwashing detergent (Mama Lemon), and that has worked in place of the expensive neem oil spray.

I really hope that my story and pictures of plant diseases do not discourage anyone from taking up high-rise container gardening! 2020 is the UN International Year of Plant Health. Living in Singapore, we may not take plant health as seriously as communities whose very subsistence depends on it. Still, we can all do our part to understand and promote a cleaner and greener Garden City. Sincerely wishing any prospective gardener – green fingers, thumbs or none – much satisfaction and enjoyment that plants bring!

References

Walls, Ian G. (1984).  A-Z of Garden Pests and Problems: identification and control. London: Treasure Press.

Pest Solver. (2020). How to Get Rid of Mealybugs | Planet Natural. [online] Planet Natural. Available at: https:/www.planetnatural.com/pest-problem-solver/houseplant-pests/mealybug-control/[Accessed 20 Feb. 2020].


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Written by Samuel Eio
Illustrations by Jasreel Tan

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