Sometimes when you buy a houseplant, you’ll find its leaves are particularly shiny. Now, this can be innate—the leaves of certain plants, and in particular those of schleffera (Schefflera actinophylla), zz plant (Zamioculcas zamiifolia) and mirror plant (Coprosma repens), are naturally very glossy—but often what you’ve found is a plant that was treated with leaf shine, also called leaf polish. Florists, especially, like to add value to the foliage in their floral arrangements and so spray the leaves with it. They also tend to apply it to the houseplants they sell. And leaf shine products are readily available in stores and on the Internet for you to use yourself.
So, leaf shines make leaves glossy, but are they good for plants?
Manufacturers claim they are. They say they remove dust, dirt and lime deposits, help the leaves breathe better, reduce evaporation and prevent dust from recurring. And, of course, that they “leave the foliage glossy and bright,” which is apparently a desirable thing.
And it is true that, in general, these products are not terribly harmful: your plants won’t keel over and die immediately after you apply them. However, they’re not without undesirable side effects either.
What makes things complicated is the ingredients often seem to be a company secret. It’s hard to know what they contain. And each leaf shine product is different. Some contain silicone, others different oils and waxes … and all these are products that can do some harm if not properly applied.
First though, there is no disadvantage to applying leaf shine to cut leaves, as florists do when preparing flower arrangements. The moment these leaves were harvested, their death was inevitable, usually within a week or two. To make them shine for what’s left of their life doesn’t change the eventual outcome.
Leaf shine is also recommended to remove dust and grime on plastic and silk plants and give them a “healthy sheen.” (Yes, one label actually says that!) They’re unlikely to harm fake plants and, besides, I’m a gardener. I honestly don’t care what happens to artificial plants!
The situation is much more complex in the case of living plants, especially ones you want to keep alive.
When the label states that the product helps the plant breathe better, but assures at the same time that it also reduces water loss due to transpiration, this is actually contradictory information. Plants do most of their breathing via stomata, pores that open to allow gaseous exchange (respiration), but in doing so, they also allow water to escape (evapotranspiration). Anything you do to increase a plant’s respiration will also increase transpiration … and anything you do to reduce evaporation will decrease respiration. What manufacturers are claiming is kind of a horticultural case of having your cake and eating it too.
Theoretically, although this is not always made clear on every product label, you should only be spraying the upper surface of the leaf with leaf shine. If you spray the underside of the leaf, where the majority of stomata usually are, it may block them and thus reduce the plant’s respiration … and by consequence, its development and even survival. On plants with stomata only on the underside of the leaf, leaf shine will not negatively affect respiration.
However, coating the upper surface with oil or wax has another undesirable effect: it reduces photosynthesis. Not a lot, but a little. Any coating shiny enough to make the leaf appear glossy also reflects light and, of course, light that is reflected is not absorbed. Essentially, spraying your plant with leaf shine is the equivalent of covering it with shade cloth.
Since lack of light is the major negative factor in maintaining plants indoors, leaf shines, although they only reduce photosynthesis to a fairly small degree, can nevertheless be harmful to plants already lacking light, slowly undermining their health.
If you read the product label (so few people do!), you’ll notice it usually recommends that you not apply leaf shine to certain plants, such as plants with fuzzy leaves, like African violets), succulents, ferns and flowering plants. Some state things the other way around and suggest using only on “houseplants with hard-surfaced leaves.”
What is not made clear, at least not on the leaf spray products I have seen, is that it is best to never apply it to monocots of any sort, because unlike dicots, most of whose stomata are on the lower surface of the leaf, in monocots, the stomata are distributed fairly evenly on both sides of the leaves. Leaf spray can seriously impinge their respiration.
So, it’s best to not apply leaf spray to such monocots as yuccas, orchids, dracenas, bamboos, sansevierias, etc. nor any of the aroids (philodendrons, photos, monsteras, dieffenbachias, peace lilies, etc.). It is even more important to never apply it to bromeliads, especially the famous “air plants,” which absorb almost all their moisture from scales on their leaves, as leaf spray will clog the scales. Avoid applying it too to aquatic plants with floating leaves, as they only have stomata on the upper surface of the leaf.
When you start to make a list of the plants you shouldn’t really use leaf spray on, you’ll find it includes nearly two thirds of the most popular houseplants!
When Not to Spray
The small print will also likely warn you against using leaf spray:
- In hot weather;
- On sunny days;
- When the leaves are wet;
- On young shoots.
It sounds to me like they’re saying to only apply it to dormant plants … and after dark!
Homemade Leaf Shine Products
Do-it-yourselfers will find plenty of sites on the Web proposing homemade products to give houseplant leaves a shiny appearance: margarine, mayonnaise, olive oil and many, many more. In general, these products do make leaves shine … but the restrictions above still apply: they decrease the availability of light and harm respiration if not applied correctly. Also, homemade coatings are usually very sticky and quickly become covered with dirt, dust and pet hair. Not only are they no better for your plants than commercial products, they’re actually worse!
Giving Leaves a Natural Luster
Having gone over all this, I think it’s time to ask the real question: do you really need leaves that look lacquered?
It seems to me that the natural luster of a leaf should be enough. That a philodendron should look like a philodendron and a ficus should look like a ficus, not like they were made of patent leather!
To that end, all you really have to do is to clean the foliage of your houseplants from time to time to remove the dust and dirt that dull the natural brightness of the leaves. Sometimes simply hosing down the plant in the shower (or outdoors in the summer) is enough. If not, simply wipe the leaves with a soapy cloth to get rid of the grime, then rinse. Lime deposits (hard, white, crusty buildups) can be tough to remove with soap alone. Remove them by rubbing softly with a cloth soaked in a solution of 1 tablespoon of white in 1 quart (1 liter) of water.
Leaf shine products: thanks, but no thanks!