Poison ivy. Poison sumac. You’ve probably heard of these, but how about poisonwood? Or manchineel?
Some of Southeast Florida’s forests harbor these toxic native trees that you need to learn to identify before you go wandering into the woods.
But let’s get the basics of our irritating plants down first, since five of them are related by one thing, urushiol, an oily resin that can irritate your skin.
Allergic contact dermatitis, as your doctor will call it, is the primary problem caused by urushiol. Only a billionth of a gram can cause a reaction in some people. Some people have no reaction to small doses of urushiol at all.
As hikers, we do our best to stay out of trouble when we go walking in the woods. And so the most basic heads-up of all is about the existence of three troublesome plants in Florida that cause skin irritation. They’re found in many other states as well, but once our growing season gets going here, some habitats are just overrun by these irritants.
If you’ve grown up playing in the woods, you’re probably very familiar with poison ivy. It causes more skin rashes than any other plant in Florida because it contains urushiol.
Some people are only slightly affected by poison ivy, while others have massive itchy outbreaks if they brush against it.
I learned the hard way – clearing an acre of it with my father many decades ago – than even if you aren’t sensitive to poison ivy, you can become permanently sensitive to it if you touch enough of it.
Poison ivy (Toxicodendron radicans) grows both as a ground cover and as large vines that climb trees and almost mimic hickory leaves in their size.
It is found everywhere in the state, but some habitats are more poison ivy-rich than others. It likes the deep shade of hardwood hammocks and tropical hammocks, but we’ve also seen it pine flatwoods and floodplain forests, too.
Far less common in Florida than in other states, poison oak is still present here.
Poison oak (Toxicodendron pubescens) is a small shrub that has the same structure as poison ivy – remember “leaves of three, let it be.” It can grow up to a few feet tall and it looks a lot like a small oak tree, as the leaf shape mimics an oak.
You’ll only find it in North Florida, from Levy and Marion counties through the Florida Panhandle. And it’s very easy to mistake for an overgrown poison ivy.
We’ve noticed it along many trails, always in shady areas, but especially on one particular visit to San Felasco Hammock Preserve, where it seemed to be very common.
You may be familiar with the rather common winged sumac found in sandhill habitats. Poison sumac (Toxicodendron vernix) is found from Central Florida north.
Liked winged sumac, poison sumac leaves start turning reddish-orange in the fall. But these shrubs are taller and have reddish stems. Unless you are looking for them, they may not catch your attention.
We’ve come across them in sandhill areas, particularly in the transition zone into a hardwood hammock. Ichetucknee Springs State Park is one place we definitely recall seeing poison sumac.
Now we get into the mean stuff. And by mean, we mean deadly. Both poisonwood and manchineel are native trees, but they are downright dangerous.
The endangered white-crowned pigeon eats the plums that grow on both trees, but you can’t.
There’s a reason the fruit of the manchineel was called the “little apple of death” by Spanish explorers. A taste of these caustic fruits could kill you.
Poisonwood (Metopium toxiferum) is found from Key West north to Stuart and across the Everglades and Big Cypress.
You’ll find poisonwood growing along the trails of Everglades National Park, Long Key State Park, National Key Deer Refuge, along the Overseas Heritage Trail, and in dozens of other natural lands in Southeast Florida.
As you might guess by its name, you do not want to touch this tree. Even by accident. It’s the number one reason you should never bushwhack through a tropical forest in the Keys or Everglades.
I’ve been told that the urushiol in poisonwood bark, sap, and leaves is 100 times more potent than poison ivy. It’s smart to avoid hiking in the rain in tropical hammocks because you do not want the sap dripping on you.
Identifying mature poisonwood is relatively easy. The trunk of the tree has weepy black spots like oil is leaking out of the trunk. That’s urushiol seeping out.
In both mature and young trees, the bright green leaves are droopy like the tree hasn’t seen enough rain. Each leaf is tipped with a bright yellow rim around it.
Manchineel (Hippomane mancinella) is a Caribbean tree that grows in the Florida Keys and Everglades.
Every part of the manchineel tree is poisonous. Contact with this tree can be fatal.
Manchineel is part of the Euphorbia family, which includes poinsettia. A milky sap oozes from this tree and its leaves.
It’s thought that Carib Indians tipped their poison arrows with the sap. It is the most toxic tree known in the Americas, and is found from Southeast Florida south through Central America.
Unlike poisonwood, where you need to have touched oozing sap or a broken limb or leaf to irritate your skin, manchineel is simply nasty all over, all the time. Don’t ever stand under one.
We’ve seen manchineel at both Key Largo Hammocks and Everglades National Park, as well as in National Key Deer Refuge. There are other known localities with it remote areas of the Florida Keys.
More than a decade ago, a ranger warned me about manicheel in Everglades National Park. I was working on 50 Hikes in South Florida and wanted to tackle a particular trail that no longer seemed to be shown on newer park maps.
The ranger told me that it would not be safe for me to hike that trail, and he certainly didn’t want me sending people there. It went through a grove of manchineel trees.
The last hiker that had used it was temporarily blinded by a brush of leaves against his face. Although rangers and researchers still go out there, that trail was marked off limits to public use soon after.
While I was on a personal tour at Key Largo Hammocks Botanical State Park, a ranger there similarly pointed out its dangers and warned about getting off-trail in the park.
A botanist, he had some he grew at home. He gave me a manchineel sapling to gift to my father, who collected weird trees.
Although it was less than a foot tall, within a couple of hours along my drive home with the air conditioner on in the summer heat, I had to stop the car. My eyes and throat hurt. The tree was filling the car with toxic fumes.
I had to drive with the windows down the remainder of the trip. A decade later, after Dad had passed away, we discovered that he had very gingerly protected the tree from winter freezes in North Florida and it had tripled in size.
Mom wanted no part of it. She insisted I take it away. It lived on my porch for a while. When John first visited me, he made a comment about it and was shocked that it was what he thought it was. I was surprised he knew what manchineel was!
Fortunately, before we went to the Appalachian Trail, we were able to make arrangements to send it off into the wild. Even though it was legally obtained, it is an endangered species. I was glad to pass it off to the Florida Park Service to replant in a tropical hammock.
If you accidentally touch either poisonwood or manchineel, immediately seek medical help. Ingesting their fruit can be fatal. That’s a good reason to never, ever sample tropical plums in a tropical forest.
If either poisonwood or manchineel is on your Florida property (again, Southeast Florida) and you don’t want it there, don’t try to remove it yourself.
The sap can harm you, and the smoke from burning the limbs can cause extreme lung and eye irritation to the point of blindness. Call for an expert arborist for help with removing these trees.
Other Irritating Trees
If you are sensitive to poison ivy, there is a good chance that mango trees, cashew trees, ginkgo trees, and the invasive Brazilian pepper found throughout Florida will also irritate you.
All of these contain varying amounts of urushiol. We had a friend who was very sensitive to urushiol, and he could not eat cashews or mangoes as he would break out in a rash.
If you know you have serious sensitivity issues like that, avoid hiking in areas with Brazilian pepper and anywhere posted by land managers as having a large number of poisonwood trees.
That includes most of the natural-surface nature trails in the Florida Keys. Paved trails like the Overseas Heritage Trail and the broad paved loop at Key Largo Hammock provide more of a buffer from these trees.
Learn more about manchineel from UF/IFAS
Learn more about poison plant identification from UF/IFAS
See our article on how to remove urushiol from poison ivy from your clothes and skin