Trees can be found in the wild and when ripe the crop can be harvested. Once obtained, the crop can be combined with a sapling that is the same type of tree as the tree the crop came from to obtain a sapling that will produce that crop. In 1.9, you require 3 crop items in combination with 1 sapling. Also, in later versions, despite the grown trees being specific vanilla types (such as apples growing on oak trees, or lemons on jungle trees), any sapling, including modded ones, can be used to craft the Pam's Harvestcraft trees.
For trees with products that hang from the leaves, the item can't be harvested until it's fully mature. Once it has ripened, the player can right-click in order to harvest, and the item will drop nearby. Left-clicking an unripened fruit will do nothing, unless the button is held down; however, this will destroy the fruit completely without any drops. If the fruit is destroyed when fully mature, it will drop two items. However, once destroyed, the items will not grow back on the same tree; a new one will have to be found, or grown from a crafted sapling.
There are some types of trees whose products grow on the bark instead of the leaves, namely the Maple, Cinnamon, and Paperbark trees. For these, the logs themselves can be right-clicked once mature. Similar to the hanging fruits, destroying a productive log when mature will provide two items, but not the log itself; destroying it when immature will give nothing. Any logs covered by leaves will not bear any products, so the unproductive logs and the leaves can be destroyed without affecting the useful blocks. A notable exception is with a tool enchanted with Silk Touch: A productive log harvested with that enchantment will drop as a block, and be placed elsewhere. This will not keep any products from mature logs, so the player should be sure to harvest before breaking the block.
With items both hanging from leaves and growing on logs, bone meal (or any other fertilizing item or tool) can be used on them to quickly mature the products.
Harvestcraft supplies a large amount of trees from which you can harvest a wide variety of fruits and spices
All of the fruits grown on trees (except apples) are unfulfilling morsels and only give 1/2 a point of hunger