You’ve just noticed something curious on your street. That towering tree has a strange new mark on it. It’s not down to nature, either. This is a splash of yellow paint brushed onto the trunk in a circle. What does it mean? Well, it is definitely not something you’d guess in a hurry. But once you find out, you’ll know to stay well away come the fall.
Mind you, the yellow dots aren’t the only symbol that your city uses to send messages to those in the know. Most places across the country adhere to a color-coded system for relaying important information. So, while parking up after a long day at work, you may have seen a splash of red paint on the road outside your house. Perhaps you even spotted a pipe with a brushstroke of blue around the neighborhood on your Sunday stroll.
These colorful if cryptic markings have been a staple of U.S. cities since the 1970s, beginning in California before eventually spreading across the country. But they’re not solely seen on the streets. If you keep your eyes peeled the next time you’re out, you may start to notice that trees around you have paint on them, too. And, yes, they could include those mysterious yellow spots.
It’s actually not that uncommon for a tree to have a painted-on mark – as you may know if you’ve ever gone hiking. Parks often use color-coding systems to keep visitors on the trail. But the trees in your city aren’t required for guiding you through nature. They may even be the only bit of nature you see for miles. So, what could the yellow spots possibly mean?
We’ll give you a hint: you only ever see these brightly hued dots on a certain kind of tree. It’s a variety that has been a staple of urban centers since the 19th century, one that has endured life on Earth since the dinosaurs roamed. Even so, it needs city officials’ help to get through the fall.
And the reason why the dots are there is certainly less tragic than the incident that helped usher in the paint-drawn street markings. On a fateful day in June 1976, workers were busy carrying out municipal improvements on Los Angeles’ Venice Boulevard. At this spot, the road was being broadened.
An analysis the year before had also revealed that a gas pipeline sat a minimum of 18 inches below the level of the preliminary roadbed. So, with that information in mind, one of the men sliced into the earth, thinking that he had plenty of leeway before ever hitting anything important.
But the worker accidentally cut right into the gasoline pipeline. And the flammable liquid gushed from the opened tube – meaning the men at the site had to exercise extreme caution. As the smell of fuel filled the air, locals and passers-by were told to evacuate the area.
Heartbreakingly, though, this alert didn’t come quickly enough. The escaping fuel burst into flames, followed in their wake by vicious fireballs. Nine people died in the blaze, while more than a dozen suffered from burns. At the same time, the blast devastated virtually a whole block of the Los Angeles neighborhood.
Change came within three months of the tragedy. On September 13, 1976, DigAlert was created. This program relies on information from utility companies and local government officials to provide a detailed map of any pipelines lingering underground in a particular area.
So, California-based contractors can call DigAlert ahead of a project with the coordinates of their job site. Then, once those details are added to the system, DigAlert will determine which, if any, utility lines run under the surface at the proposed work location. And if there is something there, a message is sent out to the potentially affected utility companies. These firms will then dispatch technicians to mark out the positions of the wires and pipes.
The American Public Works Association followed suit by developing a national color code to represent infrastructure lines. And while local authorities do have control over what each color symbolizes, it’s been recommended that these meanings are the same across the country – making things easier for any itinerant construction workers.
As you stroll down the street, for instance, you may notice red paint on the sidewalk beneath you. That likely means power lines or lighting cables are running under your feet. Blue marks, on the other hand, denote potable water pipes, while green ones point to sewers or drain lines.
But you have to be a bit more wary of yellow lines – especially if you’re on a job site. Why? Well, the bright color warns that gas may be flowing through the pipes below. It could also be steam, petroleum or oil lingering beneath the surface – all of which could be dangerous if released unexpectedly.
Other colors in the American Public Works Association’s guide include orange, intended for alarm and signal lines, and white for proposed excavation markers. You may also see purple, which is a sign of irrigation or reclaimed water pipes, or pink – denoting temporary surveying.
To make things even clearer for workers, the American Standards Institute has given out relevant Pantone numbers. This helps ensure that the colors listed above are uniform at job sites across the city, state and country. And that’s not all. You see, the shapes and styles of these marks can also tell us more about what lies beneath the ground.
For example, lines painted anywhere from 4 to 50 feet apart are used to illustrate the middle of a facility. Arrows can also be used to show the direction in which pipes or wires run. And workers may even paint a diamond on the floor to reveal that there’s a duct system underground.
No matter where these marks appear, though, they help keep laborers and residents safe as city works unfold. But they’re not just seen on roadways. Yes, as we’ve already mentioned, you may also spot painted symbols on trees in your neighborhood. And these, too, have distinct meanings.
Let’s say, for example, that you see a tree in your city with an orange mark on its trunk. This says that the Urban Forestry Division has decided to chop it down. And the department may do this for any one of a slew of reasons. A tree may have to be removed if it’s dying, for one, or if it’s in the way of urban development.
Then there are colored dots that appear next to grassy patches on the sidewalk. And if you see such a mark on the cement, then you could be in luck. Typically, if the spot is in pink or orange – although other hues are sometimes used – a new tree will be arriving soon.
And then there’s the yellow that you may see splashed across a trunk. But this symbol doesn’t mean the tree will come down, nor that another will be rooted nearby. No, this marking hints at what’s going to happen in the tree’s future. You ought to know what it means, too – for the sake of your nose, at least.
Why? Well, chances are that the tree in question is a ginkgo. This variety became a popular choice in cities after it proved its resilience in 19th-century London. During that period, smog filled the skies of the English capital, making it hard for residents to see or breathe.
And yet somehow the ginkgo trees in London grew and flourished despite these unforgiving conditions. Yes, this plant species could even survive the harsh pollution created by the industrial revolution. So, the ginkgo started popping up in European cities – as well as, eventually, in the United States.
There’s solid evidence for the ginkgo’s hardiness, too. The U.S. Forest Service has calculated that the average city tree – one rooted in the downtown area in particular – has a lifespan of only a decade. Its nonurban counterparts, by contrast, usually live for at least five times that long.
But ginkgo trees are an incredible exception. Even when placed in the busiest of cities, this species can go on for centuries. And they’re able to withstand everything from pests to wind to pollution to fire. One notable example even stood firm after the nuclear blast that hit Hiroshima.
All of this sounds great, especially to city planners. But if you’re tempted to plant a ginkgo in your yard – safe in the knowledge that it’ll likely be there for decades to come – there’s one big drawback. And if you’ve ever lived in a city in the fall, you may already know why you should be cautious.
In the same manner as other trees, the ginkgo puts on a glorious fall display as its leaves change to a warm golden hue. But as the foliage and berries from the female trees start to drop, things become much less pleasant. These parts release a horrible stink that has been compared to the odor of vomit. Ew.
And this unpleasant feature has existed long before the ginkgo became a staple of downtown design. Experts believe that the trees developed their rancid stench more than 200 million years ago. This smell would work as an appetizer for dinosaurs, who would eat the foul-smelling berries. Then the beasts would roam, pooping out the seeds as they went – and helping to spread the ginkgo far and wide.
Nowadays, many people think of the ginkgo as just that stinky tree on their street or near their office. Yet the yellow dot painted on the base of your local ginkgo means that the Urban Forestry Division will be doing its best to diffuse the smell. Yes, the department uses the symbol to mark out female trees that need an application of scent-fighting spray.
In Washington, D.C., for example, just over 800 female ginkgo trees were growing in the capital as of 2018. And on three evenings, city crews coat these yellow-dotted trees with a substance known as Shield Potato Sprout Inhibitor. This pesticide not only helps the humble tater, but it also stops ginkgo berries from developing that distinctive stink.
The effectiveness of the treatment varies from year to year, however. The weather conditions at the time of the chemical application may dull its effects – and so allow the ginkgo stench to come through. And if the spray hasn’t coated the entire tree, some fruit may yet flourish.
But fortunately for your nostrils, specialists have come up with ways to prevent the smell altogether. And you may have already realized one simple solution: propagating male trees only. As male ginkgo don’t produce the rancid-smelling fruit, they obviously don’t then need to be coated with a pesticide.
So, now you know what those yellow dots mean – as well as the crucial marks painted onto sidewalks and roads across the U.S. And, interestingly, members of the public have used their own colorful messaging systems, too. There are the folks, for instance, that wanted to stop random passersby from walking onto their land.
Of course, house owners have always been able to hang “No Trespassing” signs up outside. But the law has given them yet another option to make sure that the message is crystal clear. In Arkansas and Texas, among other states, a purple-painted fence legally delineates the edge of private property.
Purple may have been chosen as it’s one of the few hues that colorblind people can still discern. So, if the edge of someone’s land is splashed in grape-toned paint, there’s no denying it: outsiders shouldn’t cross the line unless welcomed in.
Other civilian-painted symbols have carried their own meanings. Take the New Jersey borough of Dumont, for example. There, a blue stripe appeared between the double yellow lines that split the roadway in half for drivers. That’s not completely unusual, either. Sometimes, the darker hue appears on the street to help disabled motorists.
In the case of Dumont, though, the blue stripe gave way to a green one further down the road. And this may have left folks baffled. Should they be doing something differently? Was this a warning? Well, no. As it turned out, a resident had requested the paint as a way of honoring important members of the community.
Simply put, the blue line was meant to pay homage to the local police department, as it had appeared on the same road as the Dumont precinct. The green stripe, meanwhile, was intended to be a tribute of sorts to paramedics and their life-saving efforts.
And the blue line idea had legs, as other communities in New Jersey added stripes of their own to thank their local police officers. In Mantua, the cops there posted to Facebook to explain that the yellow-blue-yellow color combination “describes the concept that the police are what stand between the victimizers and the would-be victims.”
This all goes to show that the paint lines and dots you see around your city aren’t just nonsensical squiggles or neglected graffiti. They send a message – whether it’s a warning of gas lines below or a thank you to the emergency services. They may also point out the stinky tree on your street – and even that is a notice you’ll be happy to receive in advance of actually smelling it for yourself.