I have a fairly large weeping cherry approx 10 years old 8' high by
12' wide that appears to be not healthy. I live in the NE USA NYC
area. The tree sits in full sun and in a 12' to 15" planted area next
to my driveway. The soil is not very drained, nugget mulched, and soil
is hard and clay like and some roots appear to making their way to the
surface.

For the past two springs I have pruned this over the years to keep the
weeping growth more like an umbrella shape. I may have over-cut a
branch or two that was more like one of the main branches rather than
shoots. Last spring, the tree blossomed but not as full or robust as
usual. This spring same thing. Last late spring & summer the leaves
appeared not robust with 25% dead branches. I suspect this year same
thing after bloom. There's no question the tree is much alive but just
unheathy looking based on earlier years.

I noticed at the crown where all the main branches stem from there to
be a hard bulge not too normal looking with a gap in the center. The
size of the main trunk is about 7" to 8" inches. It appeared last
summer there were very small ants traveling in and out the crown and
into the tree.

I want to understand what this growth could be and why/how insects
penetrated it. I want to save it and seal that gap to stop the insect
penetration. Can you give advise on what this can be - disease or
stress, how to treat it, and how to seal the gap (what material /
where to get). Also, am I doing all the right things to keep it
healthy?

The knob is the graft area (weeping cherry trees are grafted)
These trees need good drainage and compacted soil is not good- you can
plunge a spading fork into the ground and pry back and forth to help
ease compaction.
And you could add sifted compost or used coffee grounds to the areas
you disturb. Grounds are a nice mild fertilizer and source of organic
material for the soil.
Sealants are not usually reccomended but you may want to clean any
debris out of the crown as the branches may form a bowl that never
quite dries out.
An arborist might insert a drain tube drilled into this area but it is
generally beyond home gardener skills.

Go online and read up on weeping cherries - look for websites ending
in .edu for answers that have been researched.

On Mon, 5 Apr 2010 09:32:07 -0700 (PDT), Billy
wrote:

I have a fairly large weeping cherry approx 10 years old 8' high by
12' wide that appears to be not healthy. I live in the NE USA NYC
area. The tree sits in full sun and in a 12' to 15" planted area next
to my driveway. The soil is not very drained, nugget mulched, and soil
is hard and clay like and some roots appear to making their way to the
surface.

For the past two springs I have pruned this over the years to keep the
weeping growth more like an umbrella shape. I may have over-cut a
branch or two that was more like one of the main branches rather than
shoots. Last spring, the tree blossomed but not as full or robust as
usual. This spring same thing. Last late spring & summer the leaves
appeared not robust with 25% dead branches. I suspect this year same
thing after bloom. There's no question the tree is much alive but just
unheathy looking based on earlier years.

I noticed at the crown where all the main branches stem from there to
be a hard bulge not too normal looking with a gap in the center. The
size of the main trunk is about 7" to 8" inches. It appeared last
summer there were very small ants traveling in and out the crown and
into the tree.

I want to understand what this growth could be and why/how insects
penetrated it. I want to save it and seal that gap to stop the insect
penetration. Can you give advise on what this can be - disease or
stress, how to treat it, and how to seal the gap (what material /
where to get). Also, am I doing all the right things to keep it
healthy?

Find out which type of ants, probably a kind of carpenter ant. It
sounds like the ants are feeding at the graft, the ants are chewing at
the tree and the tree is attempting to heal itself, ergo a bole would
form. Unless you kill the ants the ants will eventually win.
Carefully inspect the entire trunk from the ground up, you will likely
find a small round hole, that will be the queen's chamber entry. Get
yourself a can of pressurized insecticide that does in ants, fill any
holes and spray liberally at the graft. I would also create drainage
around the tree... dig a trench all around at the drip line, at least
a foot wide and as deeply as you can. If you're fortunate you will
break through the clay strata... fill the trench with a mixture of
sand and compost. You may need to dig a trench at the low side
radiating away from the tree.