In Pokemon Gold and Silver, berries were introduced. Since then, more berries were introduced, and many people find them to be useful in battle. They are able to heal your Pokemon’s HP, cure them of status conditions, or even boost their stats. Pokemon Sun and Moon have Berry Trees, much like Pokemon X and Y. However, the mechanics of them are a little different.
The way the Berry Trees worked in X and Y is that on most routes, there would be a Berry Tree that would drop one berry every week. However, in Sun and Moon, not only do you get between 2 and 5 berries, it regenerates every day. There are fourteen trees in total, with three each being on Melemele Island and Akala Island, and four each on Ula’ula Island and Poni Island. Each tree has a different selection of possible berries, but it is possible to get 70 berries every day.
In addition, Berry Trees are the only way to encounter Crabrawler. However, the berry tree in Berry Fields will never have a Crabrawler, while most of the other trees will only rarely have a Crabrawler (The Berry Trees on Route 10 and Poni Plains have the highest chance of having a Crabrawler). Plus, whether or not there will be a Crabrawler there is determined at the beginning of the day. If there are no trees with Crabrawler on a particular day, you will have to wait until tomorrow to see if there is. You will be able to tell if there is a Crabrawler there because the berry pile will be rustling (Note: This is currently the only way to get your own Crabrawler).