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How do you age a palm tree because they don’t have rings?

Kat -  This is a really interesting one and it’s very tough to date a palm tree because they don’t have rings.  Especially it applies to plants such as cacti and yukkas that don’t have that ring structure.  In the case of really old palms you also can’t really radio carbon date them.  This works for trees because they have the same consistent heartwood all their lives but this doesn’t really happen for palms.  Some botanists use techniques which include counting leaf scars.   Palm trees make new leaves, leaves fall off.  You can count how many scars there are and multiply it by the average time taken to grow new leaves.  It’s not great.  Really the best technique is to look at historical information.  If you can find out when an area was colonised by humans if the tree’s not a native species they probably brought it with them.  You can look at old written records, historical records, paintings, photos.  There’s not really a very good way to age a palm tree.

September 2008

Sophia asked the Naked Scientists: Hi, I was just wondering, how would you determine the age of a palm tree if it doesn't have any rings? I have not been wondering about this forever, but it's really bugging me, and you sound like a smart dude. I know how to determine the age of a tree that's got rings, but that's only if it has, well, rings. Please reply soon! -fozzyelf What do you think?
- Sophia - 11th Sep 08
It is very difficult!

Carbon dating can be used on some trees that don't have rings, but palm trees generally can't because there isn't a definable part of their trunk that has been there since the tree's early years (like heartwood).

You can do an age assumption based on the standard (average) growth rate of that variety of palm. These can be highly innacurate, though, since it assumes several things, such as growth being constant over the tree's lifespan.

The only other way is through historical records, like if the tree were in a private garden or somewhere where records of plantings are kept.
- Evie - 11th Sep 08
Carbon dating only works for ancient wood as it has significant upper and lower limits. Because C14 decay is logarithmic the standard deviation/error factor may be larger than the date obtained.
- blakestyger - 11th Sep 08
Don't they add a certain number of new fronds, on average, per year, so counting the number of stumps where fronds emerged could give a ball-park indication could it not?

Chris

P.S. I toyed with the "how do you DATE a palm tree" pun, but abandoned it...
- chris - 11th Sep 08
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