Put the plants on water has soon has 75% of the hairs on the nugs change colour,this normaly happens around the week 7 or 8 stage.But if the hairs are still white at week 8 then leave her if you can till she starts to show her colour.If you are only doing a small amount of plant say 4 and they are 3 ft tall i like to take them to the shower and rince water through the plant till the run of is clear once the plants are dry then cut down.You don't have to wait untill the plant looks dead you can over cook bud.If you are in a hydroponic sytem then you will need to change the main tank a couple of times or the water will still contain nutes..........................................tyke/..........