Rubber Tree plants (Ficus elastica), with their elegant, large leaves and upright habit, make really impactful additions to any houseplant collection. However, if you’ve ever had to prune them back, you may have noticed a milky white sap leaking from the cuts you made. What exactly is that substance?
What is Rubber Tree sap, exactly? Rubber Tree sap contains latex, a chemical compound that has historically been used to make rubber products. Although Rubber Tree houseplants produce latex, they are not commercially harvested like wild Ficus elastica or Pará Rubber Trees.
Many different plants produce latex, including most varieties of Ficus. While there are good evolutionary reasons plants developed this ability, it wasn’t until humans discovered the versatility of rubber that we began to pay closer attention to what latex actually is.
What is Rubber Tree Sap?
You may have noticed the white, milky sap that leaks from the stem of a dandelion you’ve picked. Or, perhaps you’ve accidentally broken off a bract of your poinsettia at Christmas and seen the same white sap oozing from the branch.
Just like these plants, Rubber Trees produce white sap that contains latex. Latex is a complex compound containing proteins, alkaloids, starches, sugars, and more, that coagulates when exposed to air. This elastic compound is the basis of rubber.
If you want to get super technical, most plants that produce latex do so in separate cells from their other transport systems: xylem (which transports water and minerals) and phloem (the plant’s food delivery system, transporting sugars and amino acids). When you prune a plant, the fluid it excretes is actually a combination of the contents of the xylem and phloem.
Except for the true plant nerds out there (respect!), we tend to simplify this by collectively calling anything running from the plant “sap.” So, in the case of the Rubber Tree, you’ll most likely always hear that its sap contains latex, which is mostly accurate, if not oversimplified.
Regardless, when you prune back your Rubber Tree plant, you will notice that latex oozes from the cut.
Rubber Trees in the Wild
It can be hard to imagine that the Rubber Tree you keep in your home is related to varieties that grow hundreds of feet tall out in the wild.
Ficus elastica is native to South and Southeast Asia, where climate conditions encourage the trees to grow 90-150 feet tall, sometimes even topping out around 200 feet. Part of the banyan group of figs, Rubber Trees grow arrays of buttressing roots around the base of their trunks to help support their size and weight as they grow incredibly tall.
The Rubber Trees we bring into our homes, while technically the same species, have been cultivated over the years to be much more compact and house-friendly.
Wild Rubber Trees were once harvested for their latex-laden sap as the demand for rubber products grew worldwide. However, commercial endeavors shifted to the Pará Rubber Trees (Hevea brasiliensis) because of its abundant production and the ease of harvesting. Since then, the Pará has been the world’s primary source of rubber.
What is Rubber Tree Sap Used For?
Now that we know Rubber Trees and many other plant varieties produce latex in their sap, an obvious follow-up question would be: Why? As it turns out, latex is a pretty profound substance that has many benefits to plants.
One major benefit of latex is that it is sticky and elastic and coagulates when exposed to air. This comes in mighty handy when a tree’s bark is damaged, or a branch breaks off. The latex-laden sap oozes from the wound and dries over the damaged part of the tree, forming a protective bandage of sorts to help the tree heal faster.
Another benefit to latex, at least from the tree’s perspective, is that it is known to be poisonous, or at least irritating, to many pests. Insects that feed on or burrow into a Rubber Tree will end up getting covered in sap that can kill them. At the very least, the latex can dry to a gluey paste, trapping the insect and gumming up their mouthparts so they can’t feed.
While there are definite evolutionary benefits to latex, it wasn’t until people, with our talent for utilizing natural resources, discovered new applications for it, turning it into a popular commodity.
First used by ancient Olmecs, Mayan, and Aztecs, latex was harvested to make homemade shoes, waterproof clothes, and balls for sports. Since then, we’ve continued to find more and more uses for natural rubber, putting it in mattresses, medical supplies, balloons, swim caps, rubber bands, and so much more.
Again, most of these products are made using the sap of the Pará Rubber Tree, as Ficus elastica is harder to harvest.
Is Rubber Tree Sap Dangerous?
It may not come as a surprise, given how common latex allergies are, but Rubber Trees plants are considered to be toxic to humans and animals. Now, “toxic” can be a scary word, so let me give you a little context.
Latex is a known irritant for some, but not all, people. Products like latex gloves have been known to cause skin dermatitis, which typically presents as a red, itchy rash at the area of exposure. Because Rubber Tree sap contains latex, people have found they have the same irritating reaction when exposed to it.
Overall, though, Rubber Tree plants are categorized as only “mildly toxic,” meaning that they rarely, if ever, cause any severe health issues. Skin exposure to latex usually only results in a mildly irritating rash that goes away fairly quickly. If exposed to the sap, it is best to wash your skin with soap and water as soon as possible to minimize any adverse reaction.
If you have small children or pets, special care should be taken to avoid any accidental ingestion of any part of the plant. The sap can cause the same irritating dermatitis on the soft tissues of the lips, mouth, and throat, and swallowing it can potentially cause GI distress, diarrhea, or vomiting.
Usually, all it takes to avoid this is to strategize where you are placing your Rubber Tree in your home. Taller shelves, countertops, or an elevated plant stand are typically all that is needed to keep your Rubber Tree out of reach from small hands and curious pets. For more information on toxicity and Rubber Trees, read this article.
When Might You Encounter Rubber Tree Sap from Your Houseplant?
Rubber Trees only exude sap when they are cut or damaged, so there really are only a few instances in which you need to watch out for it.
Pruning is the most common instance where you might come into contact with the sap. Rubber Trees are fast-growing, so if you prune often to keep the plant’s size down, you should be mindful that each cut will release sap.
An easy way to avoid coming into contact with sap while pruning is to wear gardening gloves and an apron to protect your hands and clothes. If you get some on your skin, quickly wash with soap and water to minimize any reaction to it.
You should also be mindful any time you are watering, moving, or repotting your Rubber Tree because any break or scrape to the leaves or bark will produce sap that you might accidentally come into contact with. Again, just be mindful and wash any skin or clothes that have come into contact with the sap.
Final Thoughts
Rubber Tree plants are pretty interesting specimens. It’s hard to imagine that the cultivated varieties we bring into our homes have wild counterparts that grow as tall as they do. It’s also fun to know that the latex-rich sap has many natural and man-made applications.
Although some precautions may be necessary, I hope you find that managing Rubber Trees and their potentially irritating sap is actually fairly easy to do and that you discover just how great of a houseplant they really are.