How Old Is My Plant Really?

During a short road trip with my partner, we had one of our trademark biological-philosophical discussions. The kind of deep conversation with no real conclusion that would bore 99.9% of people, but which allows us to fill a seven-hour drive without getting bored. Yeah, we’re a good match, I guess!

But this time, I think you would have found our conversation interesting: how do you determine the age of plants?

For a tree, it’s easy, you count the growth rings, right, but what about a houseplant? Could a cutting inherited from grandma hold fascinating secrets about time? Does the age of the mother plant add to that of the cutting?

We’re going to demystify all of this together, and I promise you’ll look at your plants in a completely different light afterward.

By the Way, What Does the “Age” of a Plant Mean?

The first trap I fell into headfirst was believing that plants age like we do. Big mistake! Plants have invented something amazing that we poor humans have not mastered: modularity. What does that mean in concrete terms? A 200-year-old oak tree produces new “0-year-old” parts every year thanks to its meristems—growth zones that constantly produce new cells.

Just imagine: you have a body that ages normally, but you can grow brand new arms and legs every year. That’s exactly what our plant friends do! They don’t age like we do—their “organs” die and are constantly reborn. And yes, before anyone else says it: I’d like that too, to grow a new back!

So, when we talk about plant age, what exactly are we talking about? Chronological age (time elapsed since germination) or biological age (actual physiological state of the tissues)? Well… both!

The Mystery of the Inherited Cutting

OK, but Audrey, my 2-year-old cutting from a 50-year-old plant, how old is it exactly?

Here we enter a fascinating philosophical area. Your cutting is a bit like cloning your grandmother: genetically, she is 50 years old, but physically, she is starting from scratch.

What does that mean in practical terms? Your little cutting can flower quicker than a seedling, it retains all the characteristics of the mother plant (resistance, color, shape) and can theoretically live just as long. The interesting thing is that it retains all the “genetic memories” of its 50 years. A plant that has been deprived of water on several occasions could therefore produce cuttings that react better and more quickly to this water stress. Everyone together: woooooow!

And what if, in 50 years, you give someone a cutting? It would have 100 years of plant memory… but the material would be 0 years old… In short, it’s difficult to give a single age to a plant grown from a cutting!

Mother Nature’s Wrinkles: Longevity Records

Get ready for a temporal dizzy spell! Some plants (but not the ones in your living room!) defy all logic with their apparent immortality.

If you thought you could impress your friends with your 20-year-old ficus, wait until you discover the true elders of the plant kingdom.

Pando, the “Quaking Giant” in Utah, is 80,000 years old. And no, I haven’t added an extra zero! To give you an idea, this organism already existed when our ancestors were painting in the caves of Lascaux. It is not a single trembling aspen, but an underground root system that constantly produces new trunks through stolons. Each individual trunk therefore has the same DNA as the others and lives “only” 130 years, but the root system itself spans millennia, constantly regenerating itself through shoots that emerge from the ground. It is the oldest known plant specimen.

Methuselah, the Bristlecone pine tree in California, quietly displays its approximately 4,800 years of age (its exact location is kept secret to protect it). This tree was there before the pyramids of Egypt! And unlike us, who show signs of aging, it continues to grow as if nothing had happened. (It doesn’t look very healthy, I admit, but that’s normal for this type of pine tree…)

There is also King Clone, a creosote bush in the Mojave Desert: a colony like Pando, forming a circle, which is believed to be 11,700 years old! These bushes continue to grow quietly in one of the most hostile environments on the planet, despite the various waves of climate change it has experienced.

Scientists Who Unravel These Mysteries of Time

But how do we know that? It’s clearly not a tree that has been perpetuating itself from generation to generation for thousands of years! Isn’t there a bit of bullshit here?

Excellent question! We have a whole arsenal of methods, some more accessible than others (and some more expensive than others…), for dating these old specimens.

Dendrochronology is the classic method: we count the growth rings. One ring = one year. Simple as pie… when the plant has visible rings! Accuracy: ±1 year.

But what about your houseplants that don’t have rings? What about tropical species that grow all year round? Or what about individuals that we don’t want to kill in order to date them?

Scientists have developed herbchronology to analyze the roots of herbaceous plants under a microscope. It’s not very well known yet, but since about two-thirds of perennial herbaceous species have microscopic rings in their roots that can be counted, just like tree rings, it’s a great alternative!

You’ve probably heard of carbon-14 dating. It works, but it costs between $350 and $1,785 per analysis, and the accuracy is only ± 20–30 years. But beware: carbon-14 will only give you the physical age of the piece you are analyzing (the branch, cutting, bark), not the age of the entire genetic lineage. For your living room philodendron, let’s just say that’s a bit of a stretch…

The revolutionary innovation is isotopic dendrochronology: we analyze the oxygen isotopes in the cellulose (tiny bits in the molecules of the cell walls)! This is the future of plant dating, but it’s still only available in specialized laboratories…

In short, there are several methods that are all more or less accurate, but when used together, they allow us to estimate the age of our most venerable specimens.

A Little Plant Philosophy to Conclude

Take Pando: if each trunk only lives for 130 years, but the root system lasts for 80,000 years, what is the “true” age of this forest? It’s a bit like that old philosophical paradox: if you replace all the rotten planks on a boat with new ones, one by one, over the years… at what point is it no longer the same boat? And if you build a second boat with all the old planks, which one is the “true” original boat?

This is exactly the question we ask ourselves with our cloned plants and cuttings: where does it begin and where does it end? The material is constantly being renewed, but the genetic identity remains, so does the concept of age really apply?

(Had we been born in another era, we would have been philosophers!)

That’s the kind of totally nerdy conversation I have on road trips with my boyfriend… That’s right, two biologists on vacation! Sounds cool, huh?

But tell me, how old is your plant? The age of its physical matter, its genetic heritage, its family history… I love stories about plants that are passed down from generation to generation!