Here's the deal with harvesting points from my experiance. There are two paths that run parallel to each other. one is on a ridge in front of the outpost (about G7). The other is along the road from the outpost to Giddius and along the ridge (G5-E6). THERE IS NO SPAWNING TIME. Once a harvest point has been harvested another one will spawn somewhere along the oposite path. If you bring along a friend, you can each work an oposite path, and bounce the points back and forth to each other. This is much faster than doing both paths yourself, and the harvest is excelent. It's like a giant game of ping pong!
The harvesting points are up on the ledge opposite the entrance to Giddeus at the western end. You can get on the ledge where it slopes down to the rest of the ground a little further east.
It is Harvested in West Sarutabaruta with a sickle. There are lots of Harvest points in the area west of the Outoust on the way to Giddius. it is the most common Harvest, I have gotten aobut 30 in a hour of harvesting.
A good way to find Harvest points is to run around oressing TAB until you target a Harvest point and then use a sickle on it.