Cob: raised Garden Beds fron Cob or strawbale. Please Help!

[Llunatree at aol.com]

We live in Gainesville Florida. We are designing garden beds and have no 
access to stone or rock. The earth here is 99.9% sand. So we want to make our 
bed border walls from cob/strawbale/earth/whatever. What can we use? What mix 
ratio of sand and straw and morter? Or Portland cement? The walls will be 
about a foot or less high for the raised beds. Can someone help us figure 
this out? We also want to die the mixture or topcoat a color but with what?
Thanks in advance.
Shawn&Jen Spencer