here's one way
Step 1: Cast of characters
8-10 empty plastic soda bottles (depending on height of your window
decorative paint that will adhere to plastic
heat shrink tubing or valve-tube attachment (5/16" female threaded coupling to 1/4" male tube coupling)
about 3-4 feet of flexible tubing (aquarium type is good)
Step 2: Prepare the bottles
cut little windows into the sides, about an inch from the bottom
Step 3: Paint the bottles if desired
Shake up the paint and spray it.
I chose a terra-cotta like color for this one
Step 4: Prepare the bottom bottle cap
To keep the bottom bottle from sliding off the tension rod while you are filling it with soil, cut a hole in it using the hot knife so that it will just fit on the tension rod.
Slide the lid onto the tension rod.
Replace the tension rod rubber cap.
Step 5: Add the bottles one by one
as you add a bottle, insert some soil and add seeds in the open windows
Step 6: Install in the window
Put a small dish at the bottom to collect any water runoff
Compress the tension down a couple of inches
Place in window and center in your drainage dish
Let the tension rod go