Very cool idea! Sounds great for lettuce, spinach, radishes...
Plastic gutters will be UV stabilized too so sun should not break them down too quickly. Could easily last a decade. if the are mounted properly with sufficient fasteners/support.
For drainage you could just drill some holes. If you have rows of them you can water & feed from the top
/..................../
, , , , , , ,
, ,
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let it trickle on through to the next and then drop down to the next row and so on....
Way cool
I need a taller fence!