Pressa is a fruit that is pretty commonly used in the Cooking Profession. Pressa doesn't really make that good of food via Cooking and is more commonly picked for the Petal it can give you. The Petal that you can use off the Pressa plant is used to dye armor. The Pressa Petal will dye an item an Orange color.
The Pressa Petal isn't the rarest or best petal that people want but some people do buy these. There are 3 different places that you can farm Pressa. Below is a quick synapsis on each place and also a picture of where it is.
Pressa in Beluslan (Besfer Refugee Camp)
This is a great area to farm for Pressa and it is pretty safe too. The area is pretty close to down, if any Elyos jump you then you can easily just fun a bit north and you're safe. While you're farming for Pressa here you can also collect Xilix Fiber, Salix Logs and Orichalcum Ore. This place has an abundance of all of these items.
The only downside of this place is many people know of all the goodies here and will come to collect from here. The good news is that there is enough crap here for 3 - 4 people to gather without having to worry about screwing people out of some collectibles.
Pressa in Beluslan (Hunibor Ice Gate)
Hunibor Ice Gate is another great area for you to farm for Pressa and other assorted goodies. You can find quite a bit of Pressa here but better yet you can also find Zeller which is a very popular herb because it is used in making the 2000 DP Food. Aside from Zeller you can find other goodies here like Mithril and Orichalcum Ore.
If you're just looking to gather because you're bored I recommend also to venture into the caves in this area to gather Ruby Ore. Whatever you choose to do this area is great.
Pressa in Morheim (Silver Mane Village Area)
The final place to gather Pressa and not the best place is right around Silver Mane Village. The only downside of this area is that the mobs are so clusterfucked together that you'll usually have to kill a few to get to one node. The main reason this area is worth mentioning thought is because it is so close to Mist Mane Village.
If you're in the upper 30's you'll be a hop skip and a jump away from Mist Mane Village if you get a group. Also if you do get a group for Mist Mane Village you can also find Pressa in there. However, be careful some people might be pissy if you're busy extracting while they're fighting. Be curtious, don't do it while they are fighting.