Epicuticular Wax | Glaucous Leaves | Farina
“Epicuticular wax”, “glaucous leaves” and “farina” are unfamiliar terms for a common occurrence in succulents, and plants in general. They refer to the whitish, cloudy film or waxy coating you see on a number of succulent leaves and stems. You may have tried to wipe it away, to find it easily wipes clean, but that there was more there than you realized. This is a perfectly natural and healthy development the plant uses for its protection. Because it bears some resemblance to damaging whiteflies and powdery mildew, it can be concerning. Let’s take a closer look at what this is all about.
Epicuticular wax is a layer of whitish film on the leaves, stems and fruits of a wide variety of plants. Among many others, you see it on blueberries, plums, red grapes, apples, kale and many succulents. It forms on the outer cuticle of the plant’s skin. This wax makes water bead up, rather than truly wet the plant. And it tends to cause dirt particles to adhere only loosely to the leaf, so that it easily washes away when a water droplet rolls over it. The wax helps to keep the part of the plant that it covers from losing moisture to the air. It also reflects UV radiation, acting essentially as a sunscreen, preventing damage to the plant in the form of sunburn. Finally, it tends to make the surface more difficult for insects to walk upon it, or to lay their eggs on it.
Epicuticular Wax on Succulent Leaves
Plants develop epicuticular wax to enable them to thrive in challenging climates. For succulents, this wax helps to maintain their stores of moisture during times of drought. It helps the plant to grow in full sun without damage, and to protect it from insect predation. For some plants, like camellias, the epicuticular wax gives the leaves a glossy appearance, with a high shine. In succulents, most often it is a soft, powdery appearance referred to as glaucous. Many succulents are described as having "glaucous leaves". In botany, glaucous leaves are any that are "covered with a greyish, bluish, or whitish waxy coating or bloom that is easily rubbed off". Most often, the succulents referred to as glaucous are those that have bluish-grey or green leaves with pronounced epicuticular wax.
Succulents with Glaucous Leaves
Many varieties of succulents have a pronounced epicuticular wax on the leaves. Ecechervia Perle von Nurnberg, the dusty pink rosette above, may be the best known. You will also see this whitish wax on many, many others. It tends to be so pronounced on kalanchoe thyrsiflora, the flapjacks or paddle plant, that people often seek help for the condition, not realizing it should be there. The white chalky dust can cake up quite a bit on the stems and the lower part of the leaves. This is not a problem, and it should be left in place to continue to do its job.
Don't Wipe Away the Wax
Because epicuticular wax provides so many benefits to the plant, it should not be wiped away. Further, it takes a very long time to come back, in succulents. The plant tends to look a bit patchy, where the wax has been removed, and will remain so for months. Choose instead to see the beauty this natural protective layer imparts to your plants. It produces an almost ethereal quality to the color, doesn't it? Use an inexpensive paint brush with soft bristles to remove soil from your succulents, or to brush away dust.
My thanks to Thelma S Cruz for the use of this echeveria photo and the one at the top of this post!
Recognizing Epicuticular Wax - Farina
Recognizing epicuticular wax, and discerning the difference between it and a pathogen or infestation lies in its purpose. This wax serves as a sunscreen, a protection against water-loss and against insects. So clearly, it will need an even "application", right? In fact, the term "farina", (often used a bit inaccurately as a synonym for this type of wax), refers to an even dusting of very fine powder. Once you know this waxy powder is supposed to be there, you will note how evenly it covers the plant. It develops on the underside as well as the top of the leaf, and equally on every leaf of the plant. And if there are locations of heavier accumulation, they occur in a very gradual fashion that appears intentional. This is an important look to recognize, as the appearance of powdery mildew and of whiteflies lacks this. Also, since this wax protects the health of the plant, make note of the condition of the leaves. Healthy, happy leaves with a very fine, very even dusting of powder that covers the entire plant is a good description of the look of epicuticular wax.
Recognizing Powdery Mildew on Succulents
Powdery mildew is a fungal disease that can harm your plants. Over time, it leaches nutrients from the leaves, causing them to yellow and wither and drop. It is highly contagious and can affect any type of plant. It appears white and a little furry or fuzzy. As you can see in this picture, it can look somewhat like the beneficial epicuticular wax. But there are notable differences. Powdery mildew forms gradually, and it tends to start on a single leaf or two, heavily covering those leaves while neighboring leaves have little to none. So it is not evenly distributed over the plant at all. Close inspection shows it to be a bit patchy rather than so even and fine as the wax.
If you are concerned that you have a plant with powdery mildew, it is important to take action. To confirm that this is the problem, if you are unsure, take a leaf to a local nursery to have someone look at it for you. Or ask an experienced gardener, or take a photo and ask others on Facebook gardening forums for confirmation. If you are battling powdery mildew, there are a number of natural and effective remedies. I highly recommend this article as a great starting point for remedies for powdery mildew.
Recognizing Whiteflies on Your Succulents
Whiteflies are tiny insects that suck the moisture and nutrients from plants, leaving a sticky residue called honeydew behind. Leaves soon wither and deform with a whitefly infestation. The insects and larva are all white, and sometimes look fluffy or furry when they accumulate. The eggs are a pale yellow when freshly laid, and brown when they are ready to hatch. Whiteflies tend to be more active on the bottom of the leaf than the top. And they do not produce a uniform, even, superfine coating of the leaf or plant like the epicuticular wax does. The honeydew they produce is sticky, and a helpful way to determine that the issue you have is whiteflies.
If you are concerned that you have whiteflies but want a second opinion, the local nursery, gardening friend and Facebook forums will be very helpful. Read more about whiteflies and how to control them here.
My preferred method for both treating a whitefly problem and preventing one from occurring is to use worm castings. Worm castings are essentially worm manure, and they are rich in minerals that make them a wonderful organic fertilizer for succulents. Among many sterling qualities, worm castings are a natural source of chitinase, an enzyme that breaks down the exoskeleton of insects. I incorporate dry worm castings into the soil when I plant a succulent, either in a pot or in the ground. This enables the plant to take in the chitinase through its roots and distribute it throughout the plant. Whiteflies and other pests sense the chitinase and avoid feeding and nesting on those plants. A worm casting tea like Hello Succulents vermicompost tea can be applied topically as a foliar spray to treat an infestation of insects - and fertilize the plant at the same time.
Thank you, Lindsy Hemmersbach, for the use of this photo!
Now you know the purpose of that white film on many of your succulents! It is epicuticular wax, sometimes called farina. Even better, you can better determine if the powdery white you see is friend or foe - a beneficial wax or signs of pathogen or infestation. In general, the wax will be very fine and very evenly distributed on your plant, where the powdery mildew and whiteflies will be more patchy in appearance. Good plant hygiene is the best defense against mildew and bugs. And embracing the beauty of glaucous leaves and their waxy coating will help you to enjoy your healthy succulents!
I hope you found this article helpful. Please take a moment to leave a comment if you have any questions, or feel free to send me an email!
Happy Succulent Gardening!
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