Then he considered less orthodox factors: the cosmic and seasonal rhythms at play and how they might be harnessed to help the clippings take root.
Grahm, who owns Bonny Doon winery on the Northern California coast, is one of a growing number of farmers in the United States employing a holistic farming philosophy sometimes called "organic-plus." Biodynamic farming views land as a self-contained living organism, encouraging respect for the soil's integrity and eschewing not just chemicals but anything that comes from outside the farm.
It developed in Austria in the 1920s in reaction to the growing use of synthetic fertilizers. Fertility in Grahm's vineyard comes from cover crops that return nutrients to the soil and manure from goats roaming the landscape.
But biodynamic farming also includes elements that might make even die-hard organic devotees recoil - consulting a calendar on the phases of the moon and the alignment of planets, and using soil preparations made with manure that's been stored in cow horns, buried for a season, then mixed with water and sprayed on the land.
Grahm, 57, is used to the eye-rolling that happens right around the mention of "cow horns." But he says people who care about the quality of their food and what goes into it should be interested in biodynamic agriculture.
"It's not just that it doesn't have toxins and it won't kill you," he said. "It's actually better for you. It lasts longer on the shelf; it tastes better."
Demeter, the organization that certifies growers as biodynamic, has 150 members in the United States who have completed or are working on the three-year transition from conventional agriculture.
Although the number is small, the membership has grown by 20 percent a year for the past four years. Biodynamic farmers often seek organic certification as well.
Grahm began following biodynamic principles about nine years ago after working with farmers in France. His vineyard was certified in 2007.
Winemakers are on the forefront of the movement in the U.S., Grahm said, in part because biodynamic farming fosters the expression of terroir - the "sense of place" a particular geography bestows on a certain grape.
"You don't deform the character of the environment," Grahm said. "You respect it. And you can taste that difference. I don't know why it works, but it works."
Other biodynamic winemakers in California include Grgich Hills Estate, Benziger Family Winery and Fetzer Vineyards.
Philosopher Rudolf Steiner laid out the principles of biodynamic farming after farmers approached him with a problem: Newfangled chemicals helped them produce more and kept down pests, but seemed to sap the vitality of vegetables and livestock.
Steiner's answer became the checklist Demeter uses in its evaluations.
"People use words like 'voodoo' and 'witchcraft.' ... The truth is, it's your great grandfather's farming. It's preindustrial," said Elizabeth Candelario, Demeter's marketing director. "Steiner's answer to them was we have to go back to the time before farms started to be viewed as factories."
Gena Nonini, 46, a third-generation San Joaquin Valley farmer who grows citrus, vegetables and grapes, is comfortable talking about some of the elements considered most esoteric by conventional farmers.
The moon, planets and sun all exert an influence on the earth, some of it in ways that can be measured, such as gravity and the ebb and flow of tides, she said. Why shouldn't they also affect the sprouting of a seed or the ripening of fruit?
"I see the farm as a symphony, and the farmer as a conductor," Nonini said. "The universe writes the music."
As for the soil preparations - made with manure buried in cow horns, ground up crystals and other unusual elements - they're just a way to gently prod plants in the direction they need to go, much like homeopathic remedies, she explained.
Still, she conceded it might be hard for some farmers to become comfortable stuffing yarrow flowers in deer bladders after a lifetime of spraying chemicals purchased by the gallon.
"It can be difficult to wrap your head around it," Nonini said. "The way I see it, it spoke to my heart first."
Two-hundred miles north, a growing number of San Francisco foodies are buying into the philosophy - or at least its results.
Mark Ellenbogen, bar manager for the well-regarded restaurant Slanted Door, uses biodynamic citrus in his drinks and features biodynamic wines on his list.
"I just see a depth of flavor that I don't see in any other product," he said. "It's hard to describe. It just tastes really good: the complexity, the intensity of flavor."
Most U.S. grocers and distributors don't carry biodynamic foods because the farms are still too small and too few to supply enough produce to meet their needs, said Bu Nygrens, purchasing manager at Veritable Vegetable, the country's original organic produce distributor.
It's also easier to sell the biodynamic philosophy with wine - a packaged good with a label that can tell a story - than with a vegetable such as broccoli, she said. But that may change as consumers think more about consuming organic, local, seasonal food - ideas important in biodynamics.
"We're trying to get people to think of things totally differently," Nygrens said, "and that's just going to take a while."