The speaker talks like a farmer giving advice, or perhaps an elder reminding someone of what matters before the work begins. The instructions are simple: plough the field, break up the soil carefully, plant the seeds. The line about preparing the soil with "absolute care" appears twice, which shows how seriously the speaker takes this small, patient task.
The heart of the poem is its admission of limits. You cannot explain how a seed becomes a tree, and you are "not so powerful." Your part is only to sow. Whatever happens next belongs to something beyond human control, and the question "Who embellishes all the next?" leaves that force unnamed. It could be nature, God, or simply mystery.
The repeated "Rain is coming" gives the poem its mood: calm, hopeful and humble. There is no panic, only quiet trust. The speaker seems to say that we should do our share faithfully and then wait.