‘Envy’ is a poem by Mary Lamb, who is best-remembered for her Tales from Shakespeare which she co-authored with her brother, Charles. But she was also a fine poet, who, in ‘Envy’, presents to us an important truth about the nature of envy and the futility of believing the grass always greener on the other side.
Perhaps the best way to offer an analysis of ‘Envy’ is to go through each of its three stanzas in turn, providing a summary of Mary Lamb’s ‘argument’ at each point in the poem. So, if you’re sitting comfortably, let’s begin.
First, a word on that title, ‘Envy’. From the title of Lamb’s poem, we already know its theme: envy is the longing for something which someone else has but we don’t. Envy, of course, is viewed as sinful in Christianity: it’s one of the Seven Deadly Sins. What’s more, in the Ten Commandments in the Old Testament, one of the commandments expressly forbids ‘covetousness’, which is more or less synonymous with envy. Don’t go wishing you had someone else’s possessions.
Mary Lamb, in ‘Envy’, makes a virtue of resisting envy: rather than commanding us not to covet what other people have, she encourages us to see the pointlessness in wishing we had what someone else has, urging us to discover the wonderful things we already have.
Envy
This rose-tree is not made to bear
The violet blue, nor lily fair,
Nor the sweet mignionet:
And if this tree were discontent,
Or wished to change its natural bent,
It all in vain would fret.
In this first stanza, she turns to nature to furnish her with her examples. We know the rose is a beautiful flower, and countless poets have 
praised a woman’s beauty by likening her to a red rose (Robert Burns’s poem is one notable example).
The rose-tree is not designed by nature (or God, if you’re of the Christian persuasion) in order to grow violets: it grows roses, and does so very well. Does the rose-tree look at the violets on a nearby tree and sigh, saying to itself, ‘How I wish I could grow violets like those!’ Of course it doesn’t: it just gets on with the business of bearing roses. The same goes for the lily, or the mignionet (another plant, usually spelt ‘mignonette’).
Besides, even if the rose-tree did sigh and wish it could bear another flower than the rose, it would wish in vain: a rose-tree longing to grow violets isn’t suddenly going to start bearing violets just because it’s that way inclined. It’s in its nature to bear roses, and will continue to do so.
And should it fret, you would suppose
It ne’er had seen its own red rose,
Nor after gentle shower
Had ever smelled its rose’s scent,
Or it could ne’er be discontent
With its own pretty flower.
Mary Lamb continues this line of argument in the poem’s second stanza. If the rose-tree did fret or worry, wishing it could start bearing some other flower, anyone looking at it would conclude the rose-tree was blind to its own beauty. ‘Why, how on earth, rose-tree, can you long to bear some other flower when you can grow those beautiful roses? You must be mad!’ And this is to say nothing of the pleasant scent of the rose, its natural perfume, especially after it’s rained and the flower is slightly damp.
Like such a blind and senseless tree
As I’ve imagined this to be,
All envious persons are:
With care and culture all may find
Some pretty flower in their own mind,
Some talent that is rare.
In the poem’s final stanza, Mary Lamb makes the ‘message’ of her poem plain: all envious people are like such a (hypothetical) rose-tree, looking at others and thinking, ‘Why can’t I have what they have?’ These people are ‘blind’ to their own talents or qualities, just as this imagined rose is oblivious to its beauty and scent. If these people looked within themselves, they’d find some rare talent like the ‘pretty flower’ that is the rose.
Envy is an emotion that Shakespeare had captured several centuries before Mary Lamb, in his Sonnet 29:
When in disgrace with fortune and men’s eyes
I all alone beweep my outcast state,
And trouble deaf heaven with my bootless cries,
And look upon myself, and curse my fate,
Wishing me like to one more rich in hope,
Featured like him, like him with friends possessed,
Desiring this man’s art, and that man’s scope,
With what I most enjoy contented least;
‘Desiring this man’s art and that man’s scope’ (later co-opted by T. S. Eliot, with ‘art’ altered to ‘gift’, for the opening of his 1930 poem Ash-Wednesday) strikes at the heart of what envy is. We desire what we do not possess. But as Mary Lamb makes clear, we should look within and find the gifts and talents we already have.
‘Envy’ is written in a combination of iambic tetrameter and iambic trimeter: that is, lines composed of four iambs or three iambs. Specifically, third and sixth lines of each stanza are in trimeter, so one foot shorter than the other lines. We can see this if we highlight (using capitals) the heavily stressed syllables in the first stanza:
This ROSE-tree IS not MADE to BEAR
The VIO-let BLUE, nor LI-ly FAIR,
NOR the sweet MIG-nio-NET:
And IF this TREE were DIS-con-TENT,
Or WISHED to CHANGE its NAT-ural BENT,
It ALL in VAIN would FRET.
This combination of iambic tetrameter and iambic trimeter lends ‘Envy’ a ballad-like feel, making it almost like a song. A sweet song, with a sweet message, we might say.