When you think of farming, you probably think of food. That is, after all, the fundamental magic of agriculture: that it takes sunlight, soil, air and water, and transforms them into a source of sensory pleasure and sustenance.

But before long, the top crop in Ventura County won't be something you eat. It will be something you plant in your yard to look at.

Nursery stock has been slowly creeping up the list of the county's top crops. It ranked second last year, at $213.7 million, and Agricultural Commissioner Earl McPhail told me earlier this year that he expects it to overtake strawberries -- at $328.6 million, the top-valued crop in 2005 for the seventh consecutive year -- within the next three years or so. Nursery stock ranked fourth among county crops in 2000, with a value of $155.5 million. A decade ago, it ranked fifth and was worth $75.1 million.

Some of what's counted in that tally is young vegetable seedlings sold to farmers for transplant into their fields, so some nursery stock indirectly becomes something you eat. But a significant share of nursery-stock production is ornamental plants for sale to retail nurseries and commercial landscaping contractors. When you peruse the selection of rose bushes for sale at the local garden store, or marvel at the full-size trees that appear to have popped up overnight in a newly constructed subdivision, you are seeing the product of Ventura County's booming nursery industry.

They may not, strictly speaking, produce food. But the growers who run commercial nurseries are farmers just the same, subject to the same whims of weather and consumer preference, engaged in the same battle against pests and disease. Or so I discovered when I paid a visit to one of the county's big commercial nurseries, Otto & Sons Nursery outside of Fillmore.

I met Scott Klittich there on a foggy day in early autumn, and he drove me around in the chill, damp air for a look at the operation. As our electric cart bounced along the dirt roads, I soon found myself surrounded by 120,000 rose trees and bushes, their colorful blooms dripping with dew. Other ornamental plants stood in rows along the edges of the property, about 38 acres off Guiberson Road. The nursery covers 22 acres; the rest is occupied by an ancient orange orchard.

Klittich, the managing owner, said Otto & Sons specializes in roses, which account for 70 percent of the business. They carry as many as 900 varieties -- heaven for rose fanciers, some of whom border on the fanatical. The nursery buys its plants as seedlings from breeders, and then raises them until they're large enough for sale, mainly in 1-gallon, 5-gallon or 15-gallon pots. The plants spend no more than two years at the nursery. If he hasn't sold a rose by then, Klittich figures it's unlikely to ever sell, and the plants eventually become root-bound and start to decline.

But guessing what varieties are going to be hot a year or so in the future is an uncertain business. Like any other growers, nursery owners have to predict where the whims of consumer preferences will take the market, and try to ensure that the crop they plant today is one the public will want to buy when harvest time rolls around.

"Every year, I learn that what I think doesn't matter," Klittich said.

And like food producers, who have learned that consumers prize appearance over practically any other attribute of a fruit or vegetable (with the possible exception of price), nursery owners live in dread of plant maladies or unkind weather that can compromise physical perfection: brown leaf tips, scarring, ragged holes chewed in foliage.

"It's cosmetic, but our business is all cosmetic," Klittich said.