This could help explain why, in a 2009 survey of hundreds of thousands of Americans, the United States Centers for Disease Control and Prevention found that Americans ate no more vegetables than they did in 2000, despite all the public education about the benefits of a plant-based diet, and despite the availability of a far greater variety of vegetables. A market research firm, the NPD Group, says Americans eat an average of a little more than a cup of vegetables a day and a little more than a half-cup of fruit, or about a quarter of what the government recommends.

To help her students truly embrace vegetables, Ms. Welsh says that she has learned to address kitchen psychology along with cooking skills: less-experienced cooks have a persistent sense of responsibility toward the expensive, carefully raised produce that they buy and the corresponding feeling of guilt when that produce isn’t used to its full potential.

“There are all these expectations to perform complicated tasks that they have no training in,” she said. “They are set up for crushing failure.”

In the face of vegetable anxiety, what’s an aspiring omnivore to do?

At her school, Purple Kale Kitchenworks, Ms. Welsh counsels her students to cook vegetables the day they come into the kitchen, peeling and roasting them separately in plain olive oil and salt. “If you mix them together, you’ll have a great side dish for one day, but it won’t be so appealing the second day, and on the third day you’ll hate it.” Try to shop in stages, or schedule a C.S.A. pickup when there are a free couple of hours at the end of the day. Set the oven to 375, use large half-sheet pans and fill the racks of your oven to capacity.

Already-cooked vegetables are the key to a refrigerator filled with usable, tamed ingredients that can immediately be turned into other dishes: pasta sauces, pizza toppings and composed salads, to name just a few. Raw, they are just slouching toward rot; cooked, they are tools you can use.