David Hare-Scott wrote:
Bob F wrote:
I've just been told that the curled under leaves on my italian prune
trees are caused by magnesiom deficiency and I should apply a few
pounds of epson salts under each tree.

Is the diagnosis likely to be accurate? Location is Seattle.


I don't know about leaves curling, I thought magnesium deficiency
cause leaf yellowing especially in older leaves. Can you provide a
photo?

Photo here (I hope)
http://www.flickr.com/photos/68364065@N07/6220401824/


What kind of store wound I go to for a good price on 50 or 100 lb
bags of epson salt?

A few pounds per tree seems quite excessive to me, this is a trace
element not a major nutrient. If you over-do it you won't have a
problem with curling leaves 'cause you wont have any leaves at all. Another
problem is that epson salts is very soluble and unless it
binds to humus or clay colloids it will leach out quickly.

Here is another method that may be work if it is Mg deficiency. Treat some (or
all) trees with a foliar spray of epson salts,
possibly repeated in a week, if it is Mg deficiency they will recover
quite quickly, that is within weeks. For the longer term treat with
dolomite which will slow release Mg over time.

Another possibility is that the soil is very acid which tends to lock
up some minerals like Mg so liming or adding dolomite will raise the
pH and release Mg. A dye-indicator to test pH is cheap and
sufficiently accurate for gardening and can be used in many
situations.
Acid soil is common here in Seattle I believe, and it's been a long time since I
limed the lawn, so maybe that's a better idea