Declaring the Firstfruits
How does one set aside bikkurim? A man goes down into his field, he sees a fig that ripened, or a cluster of grapes that ripened, or a pomegranate that ripened, he ties a reed-rope around it and says: “Let these be bikkurim.” Rabbi Shimon says: even so, he must again designate them as bikkurim after they have been plucked from the soil.
Exo 23:19 The first of the firstfruits of thy land thou shalt bring into the house of the LORD thy God. Thou shalt not seethe a kid in his mother’s milk.
https://www.sefaria.org/Mishnah_Bikkurim.3.3-8
Knowing that each of the seven species would have an early quantity of fruit a tradition was created of marking the earliest ripe produce to make sure it was what was offered as the firstfruits…..