We begin with Mishnah 1 of the fifth chapter, the final chapter of Maseches Ma'asros. The Mishnah deals with a person who transfers seedlings that have not yet finished growing from one place to another in his garden, his courtyard or his field. "Shesalim" are young plants - a small tree, a seedling, and even a vegetable such as a carrot that is still growing - and the person moves them from their place because the spot is too crowded, so that they will grow better elsewhere in the garden.
The rule and its definition:
As a general rule, one may not plant produce before ma'asros have been separated from it, and the basis of the prohibition is that a person should not remove the portion belonging to the kohen and the Levi. For example, if he took wheat and, before tithing it and giving the appropriate portion to the kohen or the Levi, he replanted it in his field, he would be taking for himself more than the portion that is rightfully his. However, this rule applies specifically where the plant's processing and preparation have already been completed.
Our Mishnah deals with plants that are still growing, and the person is using them for his own needs. Therefore we learned: one who uproots growing plants from his own domain and replants them in his own domain so that they will continue to grow - "patur" - he is exempt. This act is exempt from the obligation to separate ma'asros before replanting.
A further law: one who buys grain still attached to the ground:
Although we have a rule that selling produce triggers the obligation of ma'aser, that applies to produce detached from the ground. But one who buys grain while it is still attached to the ground - and for that very reason - the transaction does not obligate the separation of ma'asros, and the new buyer will tithe it at the time he harvests. "Patur" - he is exempt.
One who sends seedlings to his friend as a gift:
One who picks or uproots a plant from his courtyard in order to send it to his friend is likewise exempt from ma'asros. For the rule is that a sale obligates in ma'asros, while giving a gift does not. This is true even according to the view we saw in the fourth chapter, that there is a Tanna who holds that one who sets aside a basket as a gift basket is obligated to separate ma'asros - because his words apply to produce whose processing has already been completed, whereas here we are speaking of growing plants, which are not obligated in ma'aser.
The view of Rabbi Elazar ben Azaryah:
If the plant that was picked - a carrot, for example - has not reached the end of its growth, but has already grown to the size at which carrots of that size are sold in the market, an onlooker might think that this is a fully grown carrot. Therefore Rabbi Elazar ben Azaryah holds: "harei elu chayavin" - these are obligated. Such a carrot is obligated in ma'asros if it was sent as a gift before being replanted.
However, the halachah does not follow him, but rather the first Tanna: one who sends gifts of seedlings does not need to have them tithed.
In summary: in this Mishnah we learned three exemptions: one who uproots growing plants from his domain and replants them in his domain so that they will grow, one who buys grain while it is still attached to the ground (and the buyer will tithe at the time of harvest), and one who sends seedlings to his friend as a gift. All of these are exempt because the plant's processing has not yet been completed. Rabbi Elazar ben Azaryah obligates in the case of a plant that has grown to the size sold in the market, because of appearances, but the halachah does not follow him, rather the first Tanna.