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.
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A fragrant awakening
GREENING
As winter wears on and the days begin to lengthen, jasmine responds precisely on time, filling our nighttime gardens with its sweet, musky, spectacular perfume.
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.
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