Parameterised plant pipe for watering

I transplanted some mint into a container from my Aerogarden. It is not quite warm enough yet to put outside overnight, and after reading warnings about making sure nothing got in to it while indoors I decided to put a cardboard cover over it. This watering pipe is inserted into a hole punched through the cardboard and then in to the soil. Water with a squeeze bottle or funnel, water will slowly drain out through the holes.

OpenSCAD source included for customisation.