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Monday, 18 Dec 2017

Yarri's are tall forest trees that are sometimes called the Swan River Blackbutt, or WA Blackbutt (E. Patens to the academics). They grow in the moister parts of the Jarrah and Karri forests and are present in Roleystone in the wetter areas. Some are growing by the verge along Wymond Rd near the Old Albany Lane where there must be plentiful groundwater.

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 Yarri trees look very much like Jarrah and Marri trees and are easily confused with both. The Yarri trees have a deeply corrugated bark on the young trees or new growth, provided they are unburned (see Figure). Jarrah trees may have a dark grey fibrous bark but many have corrugations. The Marris have a ‘turtle-skin' bark and a similar habit to the other trees (and Honky nuts, of course). When burned, you can not really tell the difference between the external appearances of the three trees. All can be very straight and grow to heights of ~45m; but the straight Jarrah and Yarri have usually been removed with logging, or their habit has been contorted from the intertwining growth of neighbouring trees. Simply put, in a Jarrah forest, a Yarri tree is easily mistaken for a Jarrah and, in the past, was often logged along with Jarrah trees. Again, with lots of Marris, a Yarri tree is hard to spot; only the special nuts or the ‘Yarri Apples' give them away. 

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Small Yarri tree, about 5m tall. 

  

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Close-up of bark. Note that this young tree (~8 yrs old) is heavily corrugated. 

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Same tree. Left: note the Yarri nuts have distinctly truncated spherical shapes.

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Right: Relatively green Yarri apples.   

 

 YarriTable

 

The timber however is very different with Yarri timber having a yellow-to honey color, compared to the rich reddish-brown color of Jarrah wood. 

 

 

 

 

 

The good news however is that ordinary mortals don't have to fell the tree to identify them as there are several subtle differences that can be used to discriminate between them:

  • Yarri fruit have a distinct lip near the hole at the top (see figures below), which is absent in the Jarrah fruit.
  • The leaf shapes of the seedling Yarris are also much larger than Jarrah, and the mature leaves are narrower and a paler bluish-green.
  • Yarri flowers are much paler that the Jarrah.
  • Yarri's are resistant to the "Dieback" fungus, which the Jarrah is particularly susceptible to.

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Jarrah Fruit

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Yarri Fruit

You may also notice  the 'apples' that are special to the Yarri. (see Figure, above) These are gauls that form by the tree to try to fight an insect, the female of which lives in the gaul, the male eats (damages) the leaves.  Since there are few Yarris along Wymond road, all are infested with this insect, which only affects Yarris. So look out  for the 'apples' to identify the Yarri.

The Yarri derived it's "Blackbutt" name because it is one of the least flammable eucalyptus species and usually survives moderate forest fires with a burnt base. However, many other local eucalyptus species also survive forest fires with black butts (eg Jarrah and Marris) so the name is not really a useful descriptor.

© Roleybushcare 2017