You can find the six line text of “Twayblade” by following this link to Clive James’s review of A Hundred Doors: http://www.clivejames.com/essays/articlessince/longley
It’s a delicate and subtle little poem and it would help you to keep it open in front of you as you read.

For all his passages of heavy-handed facetiousness, Clive James makes some perceptive and sympathetic observations. However, readers who follow the link will find him using the metaphor of “wrestling” to express a curiously literal-minded response to “Twayblade”. He suggests first that he found himself actually struggling to decide whether the description of the twayblade plant was in fact a description of Longley and his companion and then that this supposed temporary uncertainty is a fault in the poem.

It seems to me that the syntactical indeterminacy at the start of the poem’s second sentence is used to beautiful effect. In line two, understanding “inconspicuous” to describe “the two of us” seems both natural and in keeping with the modesty of Longley’s sense of how human visitors to Carrigskeewaun take their place among its animals and plants. Syntactically, “inconspicuous” looks both ways, attaching itself both to “us” and to the emerging description of the twayblade. In the next line, common sense tells us instantly and without hesitation that the poet is unlikely to be talking literally about the people, and then it is quickly made clear that he is describing a plant.

I read somewhere that Nabokov used to say that one only really began reading a novel when rereading it because only then did one have a sense of the artistic whole in relation to which all its parts had meaning. That might be a lot to ask of the reader of A la recherche du temps perdu, but doesn’t seem much to ask of the reader of a six line poem. Before one arrives at that point, one of the pleasures of first reading – more faintly recaptured as one rereads – is precisely that of seeing a meaning take shape. But of course I don’t mean to defend lines two to five against the charge of unintended ambiguity on the grounds that this ambiguity is not a problem in the long run or to suggest that the momentary fantasy of twayblade-like people simply drops out of the poem when we reread it. It remains in our imaginations to clothe the literal sense of the poem with its own glow of humorous fantasy.

James refers to Longley’s “interlocutor”. He doesn’t see that Longley’s companion must be his wife, Edna Longley, to whom he has written so many love poems and with whom he has shared the love of plant and animal spotting for so many years. This is a poem of love in old age, full of almost silent depths and deeply moving. The fact that Longley recapitulates old themes so much in his work means that everything he now writes is impregnated with the memory of other things he has written. So “we find it together” speaks very simply and sparingly of how much their love is a sharing of experience and perception, a sharing of pleasures and of minds. Set against the very sensuous poems of physical love that Longley wrote for his wife in earlier books it suggests how their love has changed over time. And I think it carries a hint of something that Longley has often touched on in his poetry and referred to explicitly in prose, and that is how much his writing owes to his wife as reader.

Why assume that Edna is the companion of the poem? Well, twayblade is named for its two leaves, sometimes, as Longley says in the poem, called sweethearts. The whole point of the poem, surely, is that the plant is not only a delight to but something like a symbol of the couple, still sweethearts, still two hearts on a single stem, so that when they find it they are seeing an image of themselves as something inconspicuous with greeny petals in the long grass. If James needed to wrestle to see the sense of this he didn’t wrestle hard enough.

Within the context of Longley’s work this poem seems to me to echo his version of Ovid’s tale of Baucis and Philemon (in The Ghost Orchid). Baucis and Philemon were an old couple who prayed to the gods to die together. When the time came they were turned into two intergrafted trees. Perhaps that is rather a tenuous or private association. Whether it be so or not, the snowmelt and shadows in the last line of “Twayblade”, which James rightly praises, clearly surround the plant, and so the couple and their love, with intimations of mortality, bringing out the transience of their “today”. At the same time, it suggests that their love is fed by these things. This suggestion is further developed in the next poem but one in the volume, “Cloudberries”, where the cloudberries are described as “sweetened slowly by the cold”. You can read this tender, evocative and delicately witty poem at http://www.newyorker.com/fiction/poetry/2007/11/19/071119po_poem_longley