If you can find some small plastic bottles of perhaps the 6 to 10 oz size about like this,
you could in a south facing RV Window, create a vertical window garden that is drip irrigated. Stringing 3 to 5 off these small bottles up like this to hang from cup hook screws installed at the top of the window.
at the base of each bottle a couple holes would be drilled one above
the other (on both sides) so that nylon cord could be fed through
them and tied to make a vertical chain. with the cords tied together
at the end of the last bottle so that all of the bottles could be hung from
a cup hook or some more suitable mount.
Since it is small herb plants small bottles would be suitable. But this can be
scaled up to use 2 liter bottles for outdoor use or in the south facing window
of a home for growing small vegetables.
This website shows a construction technique.
http://www.wikihow.com/Build-a-Vertical-Garden-from-Soda-Bottles
For an RV the above photos would be scaled down. There are even systems
using a small aquarium pump that pumps from a catch basin at the bottom of
the hanging garden and fills a tank above which drips into the opening of the
top bottle. The little pump is on a timer. As shown below.
This would be ok for those who are working jobs and cannot water
the herb garden at home frequently. For those who would be
boondocking and are in camp most of the time they could just
manually water from a small water vessel. Your choice of fertilizer
would be your own option.
Spice Rack is one of my sites which will provide some information about
the use of Herbs & Spices.
http://spicerack.homestead.com/
For planting Herbs you should be aware of the PH of the soil. Here is some
information on that. Each vertical column should have a PH that matches
the herbs being grown in it.
http://www.growinganything.com/herb-garden-plants-growing-herbs-from-seeds.html