4 Bizarre Plant Symptoms that Stump Most Interiorscapers

Questions…interiorscapers always have lots of questions.

On both the industry forum, Interiorscape.com, and their corresponding Facebook page, you will find questions about problem clients, how to obtain new clients (presumably after they’ve lost the problem ones), plant issues, and pest problems to name a few. Once in a while, there’s a question about some mystery that has occured: where did that cloud of gnats come from? Why are my plant’s leaves turning yellow and falling off? And even, rarely, what in the world is THAT???

White Granules

White Granules

Philodendron ‘Congo Rojo’ showing white granules

Recently, a Facebook poster asked about mysterious white granules on the surface of Philodendron ‘Congo Rojo’ leaves at one of her accounts. My best guess from the photo and what I’ve seen over the years on plants in the Araceae family was that she was seeing the dried residues of guttation by the plant. Guttation is a process by which plants, usually under conditions of high relative humidity, cool temperatures and high soil moisture content (e.g. at night in a greenhouse), will express moisture through specialized structures called hyathodes to relieve some of the fluid pressure within their tissues despite their stomata being closed for the night.

Guttation Droplet

-Guttation Droplet

These tiny droplets may collect along the margins of the leaves and run down to the drip tips of each leaf. Or, if they are too small to collect in that fashion, the droplets simply remain in place on the leaf blade where the morning and afternoon’s rising temperatures and sunlight will dry the droplets, leaving behind the soluble contents of the liquid, mostly xylem fluid rich in sugar and mineral salts.

Salt Crystals

-Salt crystals on a Jade plant

These secretions and residues can look alarmingly like insect secretions (honeydew from scales and aphids) and can cause panic for the technician responsible for the plant’s care. While the secreted fluids themselves are not harmful to the plant, they may indicate faulty watering practices, such as watering late in the day or watering too frequently to allow healthy dry-down and aeration of the medium to occur between irrigations. The whitish deposits themselves are easy to remove if they become unsightly. A wipe-down with warm water and perhaps a bit of soap will take care of the residue.

Secretions & Residues

nectar

Aglaonema inflorescence with nectar

That got me thinking about other “mysterious” manifestations on our plants that can cause confusion and needless worry, mostly because they either resemble symptoms of real problems or because they’re just plain strange. The workhorse, Aglaonema, can throw a scare into novice interiorscapers when it begins to flower, as many do periodically. Because the role of flowers is to get some pollinator to fertilize their eggs, they often entice and reward the cooperative bee, fly or beetle with a sugary treat in the form of secreted nectar secreted. Aglaonemas will often secrete a lot of this nectar along the pedicels or stalks that support the spathes (flower-containing structures) at the tips of the stems, and when it dries it can become crystalline or crusty due to its high sugar content. Techs may mistake this substance for honeydew, which is secreted by pests feeding on the plant. The secretion is rarely a problem unless it happens to attract ants living nearby.

Dorsal Wax

Ficus dorsal wax or phenolic gland secretions

In similar fashion, Ficus species often present alarming-looking symptoms that may or may not indicate trouble. We get a fair number of calls from interiorscape clients and retail customers about the “bugs” that are attached to the base of their weeping figs’ leaves. While Ficus is certainly no stranger to pests, such as scale insects, the “emergency” almost invariably turns out to be a rubbery latex secretion or its dried residues located at the base of the leaf blade where it attaches to the petiole (adjacent to what is sometimes referred to as the dorsal wax gland or, more recently, the phenolic gland). The dorsal wax gland is a small area of specialized cells that is rich in plant phenols and can be either whitish or brown at different stages of the leaf’s development and maturity. The expressed latex will dry and remain at the site where it is secreted which can be mistaken for some sort of translucent scale insect. It’s harmless and not a sign of trouble for the plant or the technician.

But there are otherworldly phenomena that occasionally show up on Ficus that can be cause for concern. Cuban Laurel Thrips and related thrips species can attack various Ficus cultivars, deforming new leaves before they fully expand and providing a breeding ground for future generations of this pest. The plants themselves seem able to survive and grow fairly normally. However the misshapen foliage that results from the thrips and their progeny rolling the leaf blades into little cigar shaped envelopes in which to hide, render the plants unsaleable and unuseable in the interiorscape. Treatment with systemics is about the only way to attack these hidden pests. While treatment is possible, it makes more sense to remove the infested plants and destroy them to prevent the spread of the insects to other specimens.

Tumors

Crown Gall

-Crown Gall on Ficus nitida

Yet another chilling spectacle that occasionally arises on Ficus is crown gall, a bacterial infection that causes runaway growth of tumors on trunks and lateral branches of trees. The tumors themselves are scary-looking enough, being large, corky balls and clusters of lumps of tissue looking like something that crash-landed from an extraterrestrial vehicle. But all is not lost: trees will continue to grow quite normally even with a fairly heavy infection of crown galls. The galls can be repeatedly cut off if you’re careful not to damage the underlying stem tissues and sterilize your cutting tools between cuts. Clients may object to the creepy appearance of the galls on the plants, or they may not even notice them. But I guarantee that a novice tech will notice them the first time they’re encountered!

Lesions

Lesions

-Corky, scab-like epidermis on cactus

And lastly there is the sight of a corky, dry, scabby-looking lesion that can form along the stems of cacti and other succulents such as Euphorbia, which can panic an inexperienced tech or client into believing that a fatal stem rot is about to end the life of a treasured (and costly) specimen. In most cases, an older cactus plant will show some signs of this condition on its lower extremities where the older tissues of the plant are found. Opuntia cacti are prone to a disease called scab in which the cells of the epidermis (outer layers of cells) burst and curl due to excessive watering, poor ventilation and light. Other cacti, including Cereus peruvianus (column cactus) and cactus-like Euphorbia species, will develop a “bark” of dry, tough tissue along their stems as a result of sun-scorch (yes, these sun-loving plants can get too much of a good thing) and other environmental stresses that cause cells to rupture and callus over. This includes excessive soil moisture which leads to edema. This is not usually detrimental to the plant’s long-term health, all other factors being favorable, but can become unsightly in the opinion of some people.

So now that we’ve survived our little tour through the botanical house of horrors, I hope I’ve calmed your fears a bit and given you some insight into the virtual freakshow that can come to life in your interiorscape. Be vigilant, keep calm, and DON’T PANIC!

Clem Cirelli, Jr. is a career horticulturist and interiorscaper at Belmont Greenhouses in Belle Mead, New Jersey, with over thirty-five years' experience in all segments of the green industry. He holds a Bachelor's degree in Biology from Rutgers University, has written for Interiorscape Magazine, has spoken at TPIE and the Mid-Atlantic Interior Landscape Conference, and contributes regularly to the industry forums, Interiorscape.com and GreenChat.

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