You're right, zoom, it's 25. I don't think this has been changed - it's always been like that. We had what we thought were the definitive posts on this back in May 2011. I was sure it was 100, 250 and 500 for levels 2, 3 and 4 but on reflection I was never too sure about level 1. The reason for this is that most players will have already planted 1 or 2 of the trees - or more likely forgotten they have already planted 1 or 2 trees - before they get to the point of wondering and measuring how many have to be planted for Mastery.
So, the figures are 25, 100, 250 and 500 harvests of the fruit for Levels 1, 2, 3 and 4 respectively.
Crops and flowers we tend to measure differently and we use the Leaf Points rather than the number of harvests - 1 to sow and 2 to crop = 3 points a rotation - and these points (unlike trees) double each time, viz 500, 1,000, 2,000 and 4,000 for Levels 1, 2 3 and 4 respectively. That's 7,500 in total Oh my ! So, for anyone unaware of these figures until now, you now know why the climb from 3 to 4 seems to take forever because there's more work to do there than in all three previous levels combined !
I used Cocoa Trees obviously. I planted 125 of them and will continue the experiment through Levels 3 and 4 although I'm as sure as I can be that they are 250 and 500.
I'll send a PM to Sehana.