Chastetree Seed Stratification

I would like to know what is correct way and/or length of time for the stratification of the chastetree. In the Deni Bown book it states stratification consists of keeping the seed between four to twelve weeks in moist sand and peat moss at the cool temperatures of one to five Celsius degrees. Is this good enough and if so for how long should I do the stratifying?

The amount of time spent in stratification depends on the time of year the process is started, the actual temperature the seeds are kept at and the species involved.
In the spring most seeds need less time to start to germinate whereas in the fall the longest time of twelve weeks will apply. Check your seeds at least twice a week to see if any have started to germinate and as soon as you notice some roots or shoots emerging from the seeds plant them all and shift to room temperature. If nothing is coming then leave them the full twelve weeks before shifting them to room temperature. Occasionally, some seeds will not germinate after the first shift to room temperature. You then leave them for three months at room temperature and then shift back to one to five degrees Celsius for another maximum of twelve weeks before shifting back to room temperature.