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Tasmanian Blackwood Growers

Carrabin first thinning!

After my last visit to this plantation a few weeks ago I thought some urgent action was required so I offered to help with the thinning. My offer was accepted. So for the past two days I’ve been back up north helping to take this plantation to the next stage. See the following for previous blogs:

Over a day and a half we put 200 trees on the ground leaving about 100 trees still standing. A second, final thinning will be needed in 1-2 years to get the stand down to about 35 trees. The transformation over the last 2 days has been extraordinary! The plantation now looks fantastic. To the untrained eye it looks overthinnined, but in 2 years these crowns will have grown and filled in most of the gaps, and the trees will be putting on some serious wood volume.

The trees are developing some excellent heartwood. This picture shows the heartwood from two adjacent trees that were thinned. Same seedlot, same age. This is an extreme example of genetic variation in blackwood heartwood colour. The sample on the left is the more common golden brown blackwood colour and was the common colour found in this plantation. The sample on the right is a rare dark chocolate brown (if only we had known before we cut the tree down!). Both absolutely beautiful colours and indicative of what this plantation will produce in 20 years time. If only we could clone both of these colours. With a growers cooperative this could become a reality!


Having a close look at the plantation over the past two days it was obvious where the management could have been improved. Both the thinning and the pruning should have happened earlier. I don’t recommend planting 2,500 trees per hectare. But if that’s the way you want to go, then follow the New Zealand recommendation and prune to retain a minimum three (3) metres of green crown, ie. start clearwood pruning when the trees are 4 metres tall. By the time half of the trees have reached 6 metres tall you should be able to begin thinning. Pruning must be done while the trees (and hence branches) are still relatively small. Maximum diameter growth must be maintained so that pruning wounds heal as rapidly as possible (preferably within 12 months). By the time the trees are 10 metres tall the clearwood pruning should be completed. This should mean that most new pruning wounds are <3cm diameter!

This plantation has had it’s first thinning when the trees are 10-15 metres tall (far too late), and we were just completing the pruning while we were thinning! The thinning should have happened at least 8 years ago, and the pruning completed 5 years ago.

But lesson learnt. And it is still a huge credit to the owner. Easily one of the best blackwood plantations in Tasmania!

So the owners have a year’s worth of firewood to keep them warm, and their three happy goats and a small herd of cows are enjoying a major feed of blackwood greens from the thinnings.

The next tasks will be to mark and number the final crop trees and do a first measurement. Then in 1-2 years it will be a return visit for the final thinning. In 5 years time this plantation will look brilliant. A real inspiration to Tasmanian farmers. Thanks to the Carrabins for an excellent time.





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