Crassulaceae

What is the best DNA extraction method for succulent tissue?

We are testing DNA extraction protocols for Dudleya brevifolia and are able to obtain a small amount of DNA in some trials, though the same conditions do not always work consistently across multiple samples.  Thus far we have tried combinations of various protocols (QIAGEN kits, a CTAB protocol), prewash steps, tissue amounts, tissue types (whole leaf tissue, epidermal tissue, parenchymal tissue).  Another plant tested alongside Dudleya extracted well, so there shouldn't be a problem with the reagents. We're going to try flower buds next.  Any additional suggestions are much apprec