Unlike predictable spinach and romaine, you never know when arugula is going to play nicely. Sometimes the green’s spice and heat pair well with other ingredients. But just as often it asserts a peppery bite, overwhelming everything else on your plate.

Peter Volz, owner of Oxford Gardens in Niwot, explains that weather has much to do with such variations in flavor. “The hotter the weather, the spicier,” he says. A cool-weather crop, arugula makes its first appearance at Colorado farmers’ markets in early April. The arugula Volz is selling now was planted in January in a hoop house, which protects seedlings from winds and freezing temperatures. Compared to other vegetables, which might come in scores or even hundreds of varieties, arugula is straightforward. The variety Volz grows, Eruca sativa, is commonly referred to as salad arugula, with dark green leaves marked by a few offshoots, or lobes. What’s sold as wild arugula is technically Diplotaxis tenuifolia, a different genus and species altogether. The latter is hard to find, but you’ll recognize it by its leaves (it has more lobes) and more pungent flavor.

When cooking, it pays to taste your greens before committing to a recipe. Milder leaves make wonderful salads, especially when tossed lightly with extra-virgin olive oil, lemon juice, and freshly ground pepper. More pungent leaves should be blended with other greens in an impromptu salad mix. Try either in this arugula-hazelnut pesto from Alec Schuler of the recently opened Arugula Bar Ristorante in Boulder.

Arugula-Hazelnut Pesto (Serves 6)

  • 2 cups arugula, washed and dried
  • 1 cup parsley, washed and dried, stems removed
  • 2 cloves chopped garlic
  • ¼ cup lightly roasted hazelnuts
  • zest and juice of half a lemon
  • salt to taste
  • 1 cup extra-virgin olive oil
  • 20 ounces linguine
  • 4 tablespoons butter, softened to room temperature
  • ½ cup grated or shaved Parmigiano-Reggiano or Grana Padano or other hard cheese

Put arugula, parsley, garlic, hazelnuts, lemon zest, lemon juice, an ample pinch of salt, and ¼ cup olive oil in a food processor and process slowly. Gradually add the remaining olive oil until pesto reaches a uniform, creamy consistency. Cook linguine in salted water until al dente, and then drain, reserving some of the water. Toss linguine with the pesto, butter, and a little of the reserved water to thin the sauce. Serve topped with cheese.