Perhaps there's some link between the well-attested British love of gardening and the well-known British horror of sex: you don't have to be a card-carrying Freudian to follow the logic, to see how the pursuit of vegetable fertility (all those seeds and buds and those naughty stamens - goodness me!) could provide an outlet for more carnal urges. Of course, to say that this connection is typically British is not to say that it needs to be exclusively so. Islam, for instance, has matched a long tradition of horticultural excellence - the gardens of the Alhambra at Granada being the most celebrated example - with an equally venerable record of sexual repression. And in Dona Rosita, the Spinster, which Phyllida Lloyd has now staged at the Almeida in Islington, Lorca shows the twin traditions continuing into the Granada of the 20th century.

The play is a kind of dry run for The House of Bernarda Alba (which was written in the same year, 1935). In Dona Rosita, though, sexual frustration is not imposed by a fierce matriarch, but eagerly embraced, with assistance from male deception.

The action - possibly not the right word for such a static, dreamy piece - covers 20 years in the life of Rosita, an orphan brought up by a childless uncle and aunt in a middle-class household in Granada. It starts in 1890, when she is 20 years old and engaged to be married to her cousin; he is called away to be with his parents in South America, but promises to return and marry her. The second act finds her still waiting, 10 years after, apparently surrounded by willing suitors but faithful to her cousin. The bleak finale finds her an old maid of 40, while her aunt is a widow. The cousin married years ago; Rosita knew this, but preferred to go on living "in a tearful dream".

Images of flowers and gardens abound. Lloyd's languorously beautiful staging begins with a kind of tableau: nubile, black-haired women dressed in gorgeous reds and blues and greens pose fluttering their fans, looking like so many exotic plants. Rosita's uncle (Clive Swift) strides across the stage demanding to know where his seeds are; and drapes at the back of the stage rise to reveal row upon row of flowerpots (in the final act they have vanished, revealing a bare brick wall). The play's central metaphor is the "Rosa mutabile", a rose which blooms red in the morning, is white in the evening and by night has disintegrated utterly.

The sex-gardening motif is something you might expect to feel reasonably at home with; but the overriding impression is very alien, partly because it offers a distinctly old-fashioned, unBritish vision of a woman's place, partly because it pursues its ends so blatantly. Lorca needn't feel this way; the very strangeness and directness can enhance the thrill. But in Lloyd's production there's a thread of rather British coolness, a slight uncertainty of tone, which only accentuates the foreignness of the piece.

It's noticeable particularly in the performances of Phoebe Nicholls as Rosita and Eleanor Bron as the Aunt. Bron, elegant and civilised as always, never convinces you of the barrenness of her life or the wildness of her grief. Nicholls is simply miscast: she's too much English rose - pale, beautiful and affecting, but devoid of sensuality, frustrated or otherwise. It doesn't help that she never ages, instead changing her red dress for a white one as she fades. This strikes me as a directorial oversight - it seems to imply that essentially she remains the same throughout, whereas the play's message is that her destruction is total.

The tone is caught better by Celia Imrie's superstitious servant, full of earthy peasant wisdom; and Kathryn Hunter, as a poverty-stricken widow saddled with three spinster daughters - a doddering, clownish parody of old age. To begin with, both seem over the top; but over the top is what Lorca needs if the rough magic he deals in isn't going to seem merely pretty, or prissy.

Still, I don't want to overstate the flaws in a weirdly enchanting evening. The sets and costumes (by Anthony Ward and Lucy Roberts) are wonderful to look at, and Peter Oswald's translation has a very simple, fluid grace. If the production is not wholly satisfying, it's never less than intriguing.

There are further instances of the awful things men do to women in Marina Carr's The Mai, now receiving its British premiere at the Tricycle. You could call this a quirky, fairy- kissed Irish version of The House of Bernarda Alba, but that would make it sound a lot more attractive than it is.

The play revolves around several generations of women (family tree provided in the programme) cooped up, at least part of the time, in the same house. Their frustratrations are not sexual, however, but romantic. Only Grandma Fraochlan, an opium-smoking, mulberry wine-toping centenarian, has found true romance with her husband, the Nine-Fingered Fisherman, but he's long been dead. She forced her daughter, Ellie, into an unhappy marriage; and when the play opens, in 1979, Ellie's daughter, the Mai, has been waiting five years for her errant, cello-playing husband to return. This he does, but only to make her more miserable by his philandering; tragedy, predictably, ensues.

No doubt there's a moral here somewhere, but it's hard to dig it out from a cluttered and tedious story. It doesn't help that Carr's poetic intensity, which won her praise and awards for Portia Coughlan, here develops no further than sub-Yeatsian mythologising, with images of black swans and dead lovers dissolved in a lake of tears. Nicolas Kent's production has compensations - in the warmth of Judith Scott's central performance and the nicely observed period details of Agnes Treplin's design. It's encouraging, too, to realise that this play is actually a couple of years older than Portia Coughlan - so Carr's writing is improving.

The trajectory is less easy to trace in Joe Penhall's case. Love and Understanding, at the Bush, confirms the gift for dialogue he displayed in Some Voices and Pale Horse; but in other ways it's problematic.

In the new one, Neal and Rachel are a couple who are both doctors at a West London hospital - highly responsible people at the end of their tether. Their lives are disrupted when Neal's mate Richie, an egotistical, manipulative chancer with a drugs problem, invites himself to stay. The ensuing descent into suspicion and near-madness is often hilarious and sometimes touching (Penhall is marvellous at reproducing the textures of intimate conversation). It helps that it's superbly acted: Nicolas Tennant, short, pale and twitchy as Neal; Paul Bettany, tall, tan and twitchy as Richie; Celia Robertson, grave and innocent as the adorable Rachel. Mike Bradwell's direction and Es Devlin's design are both compact and ingenious.

But the whole thing suffers from a major plausibility gap: Richie is so transparently obnoxious that you can't believe they don't call the police on him within about 10 minutes of his arrival, let alone lend him money and tell him their most intimate secrets. It's also rather long. Still, if it's too much, at least it's too much of a good thing.

`Dona Rosita': Almeida, N1 (0171 3594404), to 7 June. `The Mai': Tricycle, NW6 (0171 328 1000), to 7 June. `Love and Understanding': Bush, W12 (0181 743 3388), to 31 May. Robert Butler will be back next week.