so you have less chance of damaging the roots. if you jam a bottle into the ground close to a large plant you have more chance of damaging roots. damaged roots are bad, let’s not go there, buddy.
i place the bottle at a slight angle, so that the opening of the bottle is pointed at the roots of the plant. too much angle and the ground may not hold the bottle up. too vertical and for whatever reason the water may just end up staying in the bottle. you get a slight better flow if you angle the bottle.
when you first put the bottle in you should see a couple 