| 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. |
