I would back off the watering a bit. The temps are still cool and the growing season is'tn quite here yet. HTH teddy,J

Could you have over-fertilised? Excessive nitrogen? Is the pH too alkaline (addition of mushroom compost, seaweed extract)? Magnolias must have a soil that is acidic and very low in ionic concentraion.

Hi Gb, sounds like a little to much TLC. most magnolias are carefree and thrive on neglet, if that makes sense. I see some terrible things in some negleted gardens but magnolias looks just great. Good luck. Peter R.

About 2 years ago we planted a hedge (13 plants) of 'little gems', approx 5ft tall. In the last six months we've lost 3 of them after they displayed similar symptoms described by "gardenboy" (browning of the leaves, drop-off and rapid deterioration to total death within 5-6 weeks). We've had some 'experts' have a look at them and they've suggested that some sort of bacteria in the trees (probably originating from the source nursery) looks responsible and the outcome is not good - nothing we can do but hope the others don't succumb. Recent comment from fellow garden enthusiast suggests Armillaria infection could be responsible (particularly as we've previously had cyprus pines in the same yard, and after felling and stump removal a heap of honey-coloured mushrooms appeared at potential root sites of the felled tree). Not sure what to do for this but also doesn't look good. Appreciate any comments from others who may have had similar problems or can suggest a plan of attack. With such a significant investment in our landscaping we're keen to avoid further fatalities!

hi all sounds like your tree may have a fungal infection called phythophtera . It is soil born and air born . It can occur with over watering or excess organic material...

The action plant is to drench with either fongarid or spray and drench with mancozeb and yates antirot.....

Hi guys
If you do have Phytophtera then overwatering can be one cause
What is happening is that the roots of your plants are unable to get a protection from the Phytophtera fungus which they usually would have by forming an association with Mycchoriza fungi in the soil
There are two basic types of mycchoriza and what happens is they form a symbiotic relationship with the plants, where the plants donate vitamins, amino acids and carbohydrates and the mycchoriza assist in nutrient uptake by as much as three hundred percent and also "produce antibiotics which suppress soil disease organisms"...one of which is Phytophtera
A very good explanation of this is in a book called..."ECO GARDENING- the six priorities" by Coralie Whitby and published by Rigby....pgs 22-26
I think David Suzuki did a video with this connection described in ti too...can't remember the details
The reason plants do not have this mycchorizal connection can be caused very often from aridity but in your case it sounds as if from overwatering .
It should be noted that ALL trees and shrubs do much better when they are transplanted (or planted) into a hole that has soil or leaf matter taken from the site of a similar tree or shrub...this is because the soil (or leaf mould ) contains the Mycchorizal innoculant so necessary for good plant health
In the long term the best way to assist the tree is to mulch around its base with as much litter (from the same sort of tree) as you can get.
I do not worry about collar rot (have you ever heard of a healthy tree in a natural setting (in a forest) getting collar rot from all the leaf litter around it..of course not.
If one is concerned that collar rot may occur then one could add a layer of clay around the trunk to the eventual soil level in order to insulate the trunk from the mould...this will also enable the tree to put out extra roots thus enabling it to gain further
On the other hand you could use some extremely dangerous poison such as a fungicide but please be very well protected and check that you are well safeguarded and do not inhale any fumes etc etc etc...be aware also that any fungicide will affect the many more good fungi (see above)in the soil as well as the bad targetted fungi
Good luck
Peter