SOLVED. childrens, magical, tree was hit by lightning and opened revealing the magician [s]

[Alecia]

There was book I read in grade-school (82-87), about some sort or magical/merlin character that was in a tree in a park....the tree was hit by lighting and opened revealing the magician. Kid saw it and put him in a nearby drainage pipe/culvert. When the kid come back (again & again) the culvert looks more like a cave due to "merlins" magical powers. Any ideas? Been racking my brain 4 years but can't figure it out.

[Westcoast_girl]

Found it!
The Magic Cave

[Lobstergirl, au gratin]

Alecia, was "The Magic Cave" your book?

[Rainbowheart]

Alecia never came back, but the book is in the Solved folder.

I guess The Hidden Cave must have been right.