probs digesting plant genomic

[GRANT,Patricia]

I'm trying to digest genomic DNA from mature leaf tissue for eventual ligation 
and use in inverse-PCR. I have been having problems trying to get the 
stuff to digest with the restriction enzymes of choice (PvuII or XhoI). I've 
tried several methods of genomic isolation including a quick and dirty 
arabidopsis method (thought its not arab I'm working on), then CsCl gradient 
then CTAB. None of these produced DNA which would cut with either of the 
enzymes. Finally I have included Qiagen columns (anion exchange) as the final
purification step and it now cuts when I use BamHI but won't with either of 
the others. Does anyone have any suggestions....? 

Thanks

Trish