Can you find the shire’s widest and oldest tree?

Help us find SJ’s widest and oldest tree. Put in your candidate and go into the running for a $15 voucher from Australian Native Nursery. You’ll need to focus on Jarrah and Marri trees – not only are they likely to be our oldest trees anyway, but the formula for calculating tree age by trunk circumference only works for these two species.

Open the online entry form in a separate window

Do you know how to measure the circumference of a tree?

By measuring the circumference, we can calculate the diameter of the trunk. This gives us the width of the tree. For this competition, you just need to give us the circumference in centimetres and we'll do the math. 

You will need

  • A long, flexible measuring tape.
  • A camera (your phone is fine)
  • A maps app or GPS device

How to measure

  1. Find the breast of the tree. This is the widest point 1.3 metres off the ground. If the tree forks before 1.3m, then you need to measure just below the fork.
  2. Have someone else hold the end of the tape in place and walk carefully around the tree with the tape. Keep the tape at the same height and try not to twist it.
  3. Note the number on your end of the tape when you reach the starting point. This is the circumference of the tree.
  4. Record the measurement in centimetres.
  5. Record the GPS location of the tree.
  6. Take a photo of the tree.
  7. Submit your entry. You will need to email the photo separately. 

Please note: there are no age limits to this competition. However, if you’re under 18, please put down your guardians’ contact information.

Is it a Marri or Jarrah tree?

Of all our local native tree species, Jarrah and Marri trees can be they can be the most long-lived. This means they’re almost certainly the widest native trees in the shire. If you’re not sure how to tell the difference, have a look at the PDF below.

 Jarrah or Marri? PDF

How can I tell how old a tree is?

There is a formula for calculating the age of Marri and Jarrah trees, which are two of the most important species of tree in Serpentine Jarrahdale. They’re also the oldest – if you come across a really big eucalyptus with rough bark on local bushwalk, it’s almost certainly a Marri or Jarrah.

Measuring the tree

  1. Take a tape measure and measure the tree at the widest point about 1.3 metres off the ground. If the tree forks before that height, you need to measure just below the fork. This gives you the circumference of the tree.
  2. Calculate the diameter of the tree by dividing the circumference by pi (π). Use centimetres.
  3. Now take your diameter (still in centimetres) and calculate the age of the tree using this formula:

Age = (2.35 × Diameter) + 6.97.

Example: (2.35 x 40)+6.97 = 100.97. This tree is a bit over 100 years old.

This formula only works for Jarrah and Marri trees!

Q&A

Can I put in more than one entry?

Yes.

What happens if someone submits the same tree as me?

If that tree is the winning entry, then the person who submitted their entry first will win.

Do I have to be over 18 to submit an entry?

No, you can be any age to enter! If you’re under 18, just make sure to give us your guardians’ contact information when you put in your entry.