Returning to the agricultural analogy, Alma speaks of the process of growing the plant representing one’s faith. One can learn that the experiment on the word, or the planting of the seed, was good. Alma uses the image of light, which farmers will easily understand as an essential part of the growing process. Light is good. Growing is good. It is still not a perfect knowledge. It may be, as he noted in verses 33 and 34, a partial knowledge, but it is not a perfect knowledge.
Thus, one must continue to nourish the plant. In verse 37, the plant is expressly a tree. The imagery is paralleled by the Savior’s parable of the sower (see Matt. 13:1–23, Mark 4:1-20, and Luke 8:4-15), where the seed falls on different soils and therefore has different results. In Alma’s case, the imagery isn’t to the soil, but to the care of the sapling. That the plant is a tree may invoke the necessity of continuous care for a long period of time. Trees take longer to mature than grain plants.
There are commonalities in the symbolism of Lehi’s dream of the Tree of Life and this tree of faith. Both require care, and in both cases, a good beginning can be destroyed when one ceases to care for the tree, or partake of its fruit. The fruit of the tree of life is explicitly mentioned in verse 40.