Question
My wife and I planted a 24" box Agonis(?) about a year ago. It has been very slow to grow and shows few signs of new leaves. It has been a beautiful tree other than this. Last week most of the leaves turned brown. Although it was a very hot week it was not unusual for our area.

My wife waters it every week for about an hour + with a low hose and sometimes, in hot weather, at mid-week.

My feeling is that the ground may saturated and the tree may be experiencing root damage. I purchased a moisture meter with a 10" rod. According to this the ground is wet at the 10" depth. I know that readings should be taken at a greater depth but I cannot find a suitable meter.

My question is, although it may be inaccurate, can the meter I have be an indicator of the soil water content? My thoughts are that if the ground is wet at 10" it's probably also wet at 24".

Answer
Alan,

I had to do some checking.

Peppermint tree (Agonis flexuosa) requires a dry environment with good soil drainage.  So my guess is that you are killing your tree with kindness.

The soil moisture probe you are using should be sufficient for checking soil moisture in a trees root zone.  Don't worry about going deeper than 10".  Excess moisture just drains away by gravity.

Most tree roots, greater than 99%, are in the top 14" of the soil profile.  This comes as a surprise to many folks who assume the root structure is a mirror image of the canopy.  The roots stay in the top 14" of the soil and may extend out from the trunk up to 3x the canopy diameter.   

Good luck

Gary