Alma now compares this continuum of faith to farming, something with which his listeners would have been completely familiar. The first step is to plant the seed (or faith), but not all plantings have the equal result. The seed might not be good. Environmental circumstances could prevent the seed from growing.
When a seed is planted, however, if it is a good seed and conditions are proper, it will begin to grow. This growth, visible to the farmer, provides evidence of the seed’s goodness. The seeds may all look alike when they are planted, but their value becomes evident only with the marker of growth, since only a good seed will grow.
In terms of the gospel, we may not know, when we first attempt to understand it (when at first we give place to the words), whether it is true. Alma promises only that the truth will “grow.” Only the true word will swell within our breasts in ways that we may “feel these swelling motions.”
What does this growth feel like? As I read Alma’s metaphor, it feels like an enlightened and expanded understanding. We understand more; we see more clearly. Alma’s comment that “it begins to be delicious” means that we not only understand it but find it pleasant and desirable. It increases our happiness and our clarity. This is how we can measure the growth of this particle of faith for which we have made place.