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- I had a contractor in six weeks ago who stacked a pile of soil against a grapevine trunk
and when removing it last weekend I discovered the bark had already started to rot. That
highlights the need not to change soil levels around existing plants.
- I immediately sprayed the rotting bark with copper oxychloride to stem the rot and hope
I’m not too late, but I see this problem frequently. I was just surprised that the
rot could start so quickly in winter, when the vine was dormant.
- Mulching under a lemon tree, right up to the trunk is another common cause of basal rot
of the bark too. First thing to do is remove the mulch at least 15cm (6") from the
trunk and paint the bark with a copper compound, either Bordeaux mix, copper oxychloride
or KocideŽ.
- Another and more permanent solution I often used when I was a landscape contractor and
changing soil levels around established plants, was to erect a tube of bricks around the
trunk at some 30cm distance from the trunk to allow for lateral growth. I once enclosed a
Sheoak with such a tube to a height of a metre alongside a retaining wall that was needed
and twenty years on, the tree and the wall are still standing in Burnside.
- If such a structure is beyond your means or ability, a simple solution that works most
of the time is to remove the offending soil and pack chunky gravel or stone around the
trunk to a distance of at least half a metre. Then backfill the soil to the edge of the
gravel, usually leaving a crater towards the trunk.
- It all seems a bit rudimentary, but most trees will die if you stack soil against their
trunks for any extended period of time. Some rainforest trees like the "Qld.
Box", planted as street trees throughout this area, are quite resistant to soil
inundation, but most trees are not. Shrubs are not so sensitive I’ve noted and many
will actually sprout and grow in a new shape, when their trunks are covered with soil, but
don’t take the risk, unless you are sure.
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