If someone has a nectarine tree and they like to eat one or two at a time as they get ripe. Can he do terumot and maasrot for the whole tree at one time or does he need to do it each time he wants to eat?

ב"ה Shalom This is a very important practical question for all those with fruit trees. According to Halacha one cannot take Terumot and Maaserot from fruit detached from the tree for fruit which is still attached to the tree. (שולחן ערוך יורה דעה סימן שלא סעיף נה) Therefore, each time you pick a fruit or two and bring them into your home you make Terumot and Maaserot . On the other hand, if while you are in your garden, you may pick one at a time and eat it and then pick another and eat it, without taking Terumot and Maaserot, because it is considered "אכילה ארעית" " transient eating, which doesn’t create yet the obligation to take Terumot and Ma'aserot. But you may not take any greater amount even in your garden without taking Terumot and Maaserot (רמב"ם, הל' מעשר פ"ד הט"ו הי"ח) However, while eating in the garden the law may change from fruit to fruit, therefore a Rabbi should be consulted. All the best