Hey Roger,
I've never seen HLs eat plant matter, but I have never really tried it consistently either.
I can tell you that I talked to a lady who worked at Petsmart here in AZ and she told me a tale about 2 DHL's she had for 3 years, and that they would eat chopped up romaine lettuce fairly regularly. For what it's worth....
-----
Phrynosoma.Org
Phrynosoma.Com