To actually harvest them you should need a harvest robot, and the infrastructure to run it.
You will need RF power, but in my experience, robots don't use that much of it unless they constantly moving, also Buildcraft pipes are the best way to go here, as you will need gates (specifically emerald or quartz ones, I'm assuming the former as they are more flexible.)
To start off let's get to actually making that robot. You'll need a redstone crystal (Redstone block in assembly table, with a LOT of RF), 2 diamond chipsets, and 5 iron ignots, per robot. Each robot you make will want at a docking station to call home, which is 3 iron ingots and a golden chipset.
This robot you've made doesn't actually do anything. It needs to be integrated with a programmed board. The programming table takes laser power (and not much of it) to inscribe a chosen program onto a circuit board (i think this is redstone and paper, but i forget the exact recipe.) For this you'll want a Harvester Board, and optionally a Picker one if you want a robot to pick up the produce. (Although you can use any item collection method, like hopperhocks or gather golems.) You use the Integration table to actually give the robot the program. Place the robot in first.
Now you'll want to use landmarks to mark a cube around your farm, to mark the robot's work area. This works just like marking an area for a filler, or a quarry, except for needing the 3rd dimension. You'll also want a map location (aka yellowprint). Once the area is set up, right click a landmarker to make the area border red (if you haven't already) then right click one the same landmark with the map location. It should record the area. Hang onto this you'll want it.
For just the harvester robot, you can get away with just a docking station on a kinisis pipe, with a gate also on that pipe.
The gate will need Several conditions. The ones given here are assuming you want him working all the time he can, and you aren't using redstone nearby.
Redstone signal ON > Goto station
Redstone signal OFF > Work in Area (place your map location in the section that opens up adjacent.)
If you have a gathering robot too you'll need another station on this kinisis pipe line, and another gate.
This robot also needs somewhere to dump the items it picks up. Place a transport pipe on a chest or other accepting inventory, a docking station and another gate. This MUST be in the work area.
Space in Inventory > Accept items.
It's that simple on this end, but the gate telling the robot what to do needs an additional condition, which i forget the exact name of.
Redstone Signal Off > Place Items in Area (Use a map location on the receiving docking station, then place that in the area.)
Optionally you can also filter what items it'll pick up using:
Redstone Signal Off > Filter (Place a list of items to pick up, or place them individually in the spaces)
Hope this helps, as this was typed in a bit of a rush
