Understanding the Wither Mechanic

One of the pitfalls some new players find themselves in when they first start out is planting something then not being available when it comes time to harvest that crop. When you visit a friends farm you will sometimes see this has happened to them, all their crops have withered! While there is a lot of speculation on the net regarding withering, is it random? is it timed? A little research on the official forums has lead me to believe the following;

Once a crop has reached maturity, that is, it is ready to harvest. You will have the same amount of time it took to grow before it will start withering. Now the withering itself is not instant, each individual plot will wither out randomly once the time frame has been reached.

Lets take strawberries for example, they take 4 hours to reach maturity. This means if you plant them at Noon, they will be ready at 4pm. If you miss the deadline you will have until 8pm before you need to worry about wither kicking in. However, at 8:05 the majority of your farm will still be harvest-able, only a few of the plots will be withered. This is good to know if you are working on a specific crop and are worried that you may not be available the instant it reaches full harvest. An eight hour crop will take eight hours to before it starts withering, then approximately another 4 hours before the entire farm is withered. (Roughly half the growing time for full wither, this is speculation but is generally agreed upon by the forum goers on Zynga's site.)