Re Tribulus terrestris:
Jorun - "my most hated weed here" - I can empathize with that - the number of wheelbarrow tyres I have had punctured by these blasted things!
Re H. europaeum and H. hirsutissimum:
1. Thought I'd hit pay dirt here:
'Micromorphological and anatomical comparison of two Heliotropium species, H. europaeum and H. hirsutissimum (Boraginaceae)'
in Acta Botanica Hungarica; Volume 49, Numbers 1-2/March 2007; pp.1-11
by Ö. E. AKÇÝN, G. ÞENEL and H. BAKÝ
http://www.akademiai.com/content/f4022770768h062u/But I don't know what it says! (the abstract could be more revealing)
2. Meikle, Flora of Cyprus; selected aspects of key on p.1121:
- stem with short subadpressed hairs and long spreading hairs --> H. hirsutissimum Grauer
- stem with short subadpressed hairs -->
- calyx with long spreading shaggy hairs --> H. europaeum (and only <500ft altitude)
- calyx with subadpressed upward-pointing hairs --> H. dolosum
(Cyprus also has H. supinum)
There is also Heliotropium hirsutissimum Vatke. (hmmm)
No mention of scent.
Butterflies love these.
3. Re Israel in particular: several species: some pictures:
http://www.wildflowers.co.il/english/search.asp?searchString=Heliotropium+&color=1&type=1&family=1&x=0&y=0