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Grevillea with yellow leaves

Hello,

 

            I have some Grevillea Superb that have yellow leaves and have lost most of their foliage.  I also have a Castlewellan gold conifer, in the same area which turned yellow and died.   I tested the soil it is 5pH (acidic) and the soil is also a sandy loam type soil.   It seemed to happened when we had a new mulch put down and then had a lot of rain around christmas.  Could this be root rot or just acidic soil.  My other Grevillea Superb further along is also going brown on some branches.  Please help !  I live in SE Qld.  Thanks Karen

 

Answer:

 

Hi Karen,

 

                A soil with a pH of 5 is very acid.   It is a bit unusual.  I would check it again.   But I think your problem is as you say,  root rot.   There is a fungus called Phytophera which kills Grevilleas (and may other plants) dead.   Your assumption that it came from the mulch is a good one as it is a common pest in native bushlands.   I think with the warm weather and rain the fungus has spread quickly.   There is not much you can really do about it I am afraid.   You will have to do some research and use plants in your garden which are not affected by this fungus.  I would also have a look at your drainage it is possible that the area has become sodden with water.  When plant roots have to sit in water for an extended period the leaves will start to turn yellow around the base first and then this moves to the tips eventually.  Plants will die after a couple of weeks if drainage does not start to occur.

 

Regards

Gardenguide

 

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