Jasmine, the fragrant harbinger of spring

It might happen tonight. Or tomorrow. But it won’t happen gradually. It will come all at once. All over Los Angeles, the first pink buds of jasmine will erupt into sprays of new white flowers. The display will be chaste enough for a wedding arbor -- until nightfall. Then those blameless blossoms will let rip with a decidedly frank perfume, a mix of sweetness and musk that will refuse to be upstaged by any other smell L.A. can throw at it. Exhaust. Fire. Freshly manured lawns. At that moment, the first great swelling of spring will rise over the city in a sudden night fog of jasmine.

Jasmine is not the earliest harbinger of spring. Citrus blossoms have been randomly popping open for a month now and oh so gloriously going pssssst. Box hedges lucky enough to escape weekly buzzing are suddenly surprisingly fragrant. Ornamental pears are in blossom on smoggy avenues, and the first buds are opening on Anna apples. But these are mere preambles. When the conductor wants to announce a new growing season in Southern California, he stabs the baton at jasmine.

Jasmine, at least our early-flowering species, Jasminum polyanthum, is a strangely synchronized plant. It takes a short autumn and winter chill to force it into bloom. But then, as the winter solstice passes, few other plants respond so precisely to each lengthening day. An apple tree can be tricked into bloom months early by a freak heat wave. Cherries and wisteria too. However, year after year, every pink jasmine vine will be waiting for those first days of February, when it will suddenly gas the night garden with perfume.

We humans are an accidental audience. The show is put on for moths, the doughty pollinators of so many white, night-scented flowers. To compete for daytime pollinators -- bees and hummingbirds -- you need color, and some fancy markings are useful. But to attract moths, a luminous white petal is better, along with a strong scent that vaporizes tantalizingly in the gathering dew.

The irony is that when J. polyanthum first blooms, it’s still winter, even in Southern California, and relatively few moths are on the wing. It’s chilly and wet for a bug that’s effectively a butterfly on the night shift. It seems likely that much of the first, glorious bloom goes unpollinated. The yearning explosion of scent tells us that jasmine’s new in town. It betrays the plant as a wistful import, an alien still finding its way in a foreign ecology.

Most garden books identify the poignant import as Chinese, as a woody, twining member of the olive family that came to us via the trade routes of Arabia and Europe. The name derives from the Persian “yasmin.” J. polyanthum is a close relative of the almost identical plant far more familiar in temperate zones around the world, J. officinale, or “common jasmine.” A close variant, J. grandiflorum was once at the heart of the perfume trade.

The scent rising off the petals is indeed sweet ... narcotic ... intoxicating ... all those cliches for intense good smells and more. But for the gardener, after the first rapturous snorts, there is as much wonder at what it means as how pleasant it is. This perfume floating through the night air is, effectively, the nocturnal language of plants.

A mystery to biologists

Decoded, the perfume is the plant’s hormonal system in full song, there to attract those moths. But increasingly, scientists think there is a far larger story. The ecological import of floral perfumes, where in plants it is expressed, how and when, is only beginning to be understood. Uncertainty is also the rule for how minute differences in basically the same compound can make a scent seductive or obnoxious, how it can steer this pollinator this way and that pollinator another.

Eran Pichersky, a biology professor at the University of Michigan, is a pioneer researcher in this perfumed world. The signature chemical of jasmine, called jasmonate, is a biggie, he says, or, to quote him precisely: “Jasmonate is a very important chemical in plants.” It is not restricted to jasmine but is also found in roses, citrus, many of the heavy lifters in the scented garden. What jasmonate does depends on where you find it in the plant, in what form and in what concentrations. In some cases it may attract pollinators and, in others, repel predators and even act as alarm signals to entire plant networks. Used in warehouses, it can even stop potatoes from sprouting.

Its time-honored use is in perfume. According to Cosmetics magazine, jasmine is found in more than 83% of all women’s scents and 33% of men’s. More than 5 million flowers must be gathered to produce one kilo of what the magazine calls “pure jasmine absolute.” As a result, much of the jasmine used in perfume is a chemical approximation. Once chemists start toying with jasmonate atoms, they’re not nearly as refined as plants at lining them up. What might seem small sacrifices on the molecular drawing board result in wholly detectable ones to the human nose. “But that doesn’t seem to stop the perfume industry from making a lot of money anyway,” says Pichersky.

Lingering seduction

For those of us who prefer perfume on plants rather than people, planting a jasmine vine is a far more satisfying experience than dabbing something synthetic behind our ears. Moreover, the rewards keep coming. While roses in many instances had scent bred out of them while nurserymen selected for color and form, Pichersky suspects that jasmine probably never fell afoul of breeders who sought to exaggerate one quality at the accidental expense of another, say scent. That means it could well come to us propagated in much the same form as it was originally discovered.

As such, it is a study in virtues. Unlike flowering trees, which go into bloom briefly and precariously, the vining habit of jasmine gives it lots of opportunities to flower, then keep flowering. After erupting in a crescendo of midwinter scent this week, J. polyanthum will keep flowering through May, in ever decreasing waves of blooms, until the right pollinators arrive.

For bird lovers, jasmine offers another boon. Left to run riot, it becomes a haven for bird nests in the spring, and by autumn, provided the moths show up and fertilize the flowers so they bear fruit, it provides a thick crown of berries.

For some reason, while our early J. polyanthum produces pretty fruit, it doesn’t seem to reproduce aggressively. (A personal observation: Birds scatter berries of other varieties more avidly.) In New Zealand, a country so full of exquisite birds that it features them on its banknotes, there’s no escaping it; a closely related species of jasmine, J. officinale, is a weed. That doesn’t seem to happen here with polyanthum. While birds will happily nest in vines here, they don’t seem to scatter the berries, or the berries don’t take root. Then again, it might bespeak pollination problems wrought by the early bloom. Maybe it’s as simple as the birds not liking the berries. Or something else entirely. Investigating why some things happen and others don’t is the best part of gardening.

We no longer need jasmine for the historic reasons: to cover up bad smells of open sewers and unbathed bodies. However, in so many other ways, we need jasmine more than ever, first for the romance, but also to pierce our infernal sophistication. Jasmine seduces us back into a state where we are capable of wonder at the pulses of the natural world. Aroused, we are suddenly alerted to the profound mysteries unfolding nightly in our own backyards.

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Joan DeFato, plant science librarian at the Los Angeles County Arboretum, and Scott Wilson of The Times’ library assisted with this report.

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Teasing apart the jasmine vines.

If there is a plant that argues for a switch from common English names to botanical Latin, jasmine is it. The old common names “jasmine” and “jessamine” are used interchangeably to describe plants that are often unrelated but with similar scents or flowers. Other times, the same plant might be sold under many names. This is a guide through the tangled terminology:

Jasminum: A genus from the olive family of more than 200 species of vines and shrubs, most of them fragrant. The fine-vined sorts with elegant three-part leaves, pink buds and sprays of fragrant white flowers are usually three species: J. officinale, J. polyanthum and J. grandiflorum. All are woody vines that grow up to 30 feet, produce autumn berries and can be propagated from berry or cutting. J. officinale (a.k.a. “poet’s jasmine” and “Spanish jasmine”) can endure colder climates. Early-flowering J. polyanthum (a.k.a. “pink jasmine”) is usually sold as a houseplant outside California. J. grandiflorum has slightly showier flowers.

J. sambac is thicker stemmed, with glossy evergreen leaves. Colloquially known as “Arabian jasmine,” it is actually from India and worshiped in Florida. Unsuited to our arid climate. Best enjoyed on tropical holidays. Or grown in a pot.

Stephanotis floribunda: a.k.a. “Madagascar jasmine” or “bridal jasmine.” Evergreen vine with strongly scented, tubular white waxy flowers. Not suited to Southern California, but growable with dappled light and regular water. An excellent plant for pessimists. It never quite thrives.

Trachelospermum jasminoides: a.k.a. “star jasmine” and “Confederate jasmine.” Evergreen vine with fragrant white flowers. Slow to establish but vigorous afterward; acclimates well to low water. Good on trellises or as ground cover with dwarf pittosporum.

Gelsemium sempervirens: a.k.a. “yellow jessamine” and “Carolina jasmine.” Woody vine. Perfumed but not jasmine-like. Poisonous.

-- Emily Green