As Nikkyō Niwano explains in his discussion of Chapter 5, The Simile of the Herbs, the Dharma rain falls on the roots, stalks, twigs, and leaves of all of the plants.
Roots, stalks, twigs, and leaves indicate faith, precepts, meditation, and wisdom. Roots are the most important part of plants. Without roots, they cannot grow stalks, twigs, or leaves. Therefore ‘roots’ means faith. One cannot keep the precepts without faith. Because of keeping the precepts, one can enter into the mental state of meditation and can also obtain wisdom.
Conversely, however strong the roots may be, they will eventually die if the twigs and leaves wither or if the stalks are cut. In the same way, if man does not have wisdom, his faith will become corrupt. In short, in believing in a religion, man begins with faith and attains wisdom through the precepts and meditation. However, these four steps of his religious practice are always interrelated and exist together. When any one of the four steps is lacking, his religious practice cannot be perfect, and it will not progress to the next stage. [p74]
I would substitute “practice” and “study” for precepts and meditation, but the message is the same: Faith alone is not enough.
Tiny faith, sprouting efforts to practice and a budding desire to study will surely be rewarded. As Nikkyō Niwano says later:
Even if we have only a shallow understanding of the Buddha’s teachings or can practice only a part of them, this is never useless. Every effort will be surely rewarded with the merits of the Law. But we should not be satisfied with this reward. We must always desire and endeavor to deepen our understanding and to elevate ourselves further. Thus we can use shallow faith and discernment as the first step in advancing ourselves to a higher level of faith and discernment. [p75]
But as we consider the tiny, middle and big plants we must be cautious of the categories of superior or middle or inferior.
[W]e must make clear that a big tree cannot always be said to be superior to a little one, nor a little plant inferior to a bigger one. A cedar has its proper role, and a box tree also has its own role. The small violet is beautiful, and the larger pampas grass has its own kind of beauty. In the same way, though there seem to be various differences in people’s external appearance, intelligence, ability, character, and bodily strength, all one’s qualities become beautiful and honorable when he displays his own strength to the full according to his particular nature and ability. This is the meaning of the equality preached by the Buddha. [p74-75]
No matter whether superior or middle or inferior, all advance with the three actions of body, mouth and mind:
To know the Way, to open it, and to preach it are indispensable practices for followers of the Lotus Sutra. One knows the Way with one’s mind, one opens it with one’s body, and one preaches it with one’s mouth. These are called the three actions of body, mouth, and mind, and they are the standards of the daily conduct of those who practice the Lotus Sutra by following the Buddha’s example. [p77]