You may have heard the term trichome used when describing an air plant. But what are they exactly? Trichome (trik-ome) comes from the the Greek word trichōma, which means hair. They are fine outgrowths that occur on many plants including Tillandsias. Their function is very diverse on all plants but Tillandsias primarily use them to reflect intense light and collect moisture and nutrients from the air (hence the reason we dub them “air plant”).
So how do trichomes work? During growth trichomes are living tissue. Soon afterward trichomes will die a pre-programmed cell death. Each trichome becomes a cup shaped protrusion that is individually mounted on a living dome and foot cell. When trichomes are dry they resemble open scale-like wings that point slightly upwards and when wet they swell up and lay flat against the leaves (see illustration below). This causes a small amount of water and dissolved nutrients (from dust particles or dead biomass) to get trapped between the trichome and leaf which facilitates water and food to be absorbed directly into the leaves through the dome and foot cells. At this point the water can move freely throughout the rest of the plant. Tillandsias could potentially get all the water they need if their environment was constantly humid (about 70% humidity or higher).
Trichomes come in different sizes depending on the species and some species look like they don’t have any at all. For example T. tectorum has very large prominent trichomes all over giving it a snowy appearance. Whereas T. bulbosa has small trichomes on the base and what looks like almost none on the leaves. T. tectorum is naturally found in dry, desert-like environments and need to protect themselves from intense sun while also collecting as much moisture and nutrients as possible. T. bulbosa is naturally found in wet, tropical environments in more shaded conditions.
Often times one can generalize the type of environment a Tillandsia comes from by observing the size and quantity of trichomes. The whiter and fuzzier they are the more likely you’ll find them in a bright and dry climate. The smoother, less prominent and green they are the more likely you’ll find them in a wet and humid climate. Larger trichomes can absorb more moisture from the air while reflecting more light and smaller trichomes allow large amounts of water to roll off while absorbing more light. So a general rule of thumb is if it’s whiter use less water in brighter light. If it’s greener use more water in lower light.
Tillandsia seleriana trichomes.
Closeup of Tillandsia kirchhoffiana. Notice how this species has very little trichomes.
If you’d like to learn more look for our next article coming soon, where we talk all about watering. You’ll learn some methods of watering and how frequently to do it. You will learn what effect water quality has on your plants and how your home environment plays a part in how much water they need.
Thank you for reading!
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