Iago is pretty fond of making references to gardens and other kinds of foliage, wouldn't you say? The most famous moment in the play is when Iago says:
Our bodies are our gardens, to the which
our wills are gardeners: so that if we will plant
nettles, or sow lettuce […] either to have it sterile
with idleness, or manured with industry, why,
the power and corrigible authority of this lies in our wills. (1.3.5)
This is a rather elaborate analogy between gardening and exercising free will. Basically, Iago is reminding us that he's the ultimate master gardener, so to speak, because he has such great control over himself and his actions. We're also reminded that, part of what makes Iago such a brilliant manipulator of Othello is his ability to plant the seeds of doubt and jealousy in Othello's mind.