Lace Lady Tree with shrivelled up folliage - help

[Dandytown]

My 'Lace Lady' tree was waking up from winter and showing lots of small growth from the buds.  However, when I checked it yesterday all the growth had dried up.

The area around it was treated with bonemeal and covered with black plastic mulch as this is part of my ammendment program for my pumpkins.

I'll check the soil later to see if enough water has got to the roots but can anyone think of any reason why this may of happened.

Here's a link to the tree http://www.rainyside.com/plant_gallery/shrubs/Robinia_pseudoacaciaLaceLady.html

[Dandytown]