Arugula

Arugula is one of the fastest edible crops you can grow from seed. Under cool conditions, seeds germinate in two to three days, and full-size baby leaves are ready in three to four weeks. The plant asks very little in return — reasonable soil, consistent moisture, and temperatures below 70 degrees. The catch is that once temperatures rise, arugula shifts to seed production with surprising speed, and the leaves that were peppery and pleasant become sharp, pungent, and thin. The harvest window in spring is short, and it closes faster than most gardeners expect.

Direct sow about four weeks before your last frost, or even a week or two earlier in mild springs — arugula tolerates cold and can survive a light freeze. Scatter seeds lightly and thin to four inches once seedlings are established, or broadcast more densely and harvest as baby greens by cutting at the base when they reach two to three inches. The cut-and-come-again method works well for a few weeks; eventually the plant puts energy into regrowth that is smaller and more bitter. For the best spring harvest, plan on three or four successive sowings two weeks apart.

Arugula grows in partial shade as well as full sun. In spring, partial shade can extend the season by reducing the heat load on the leaves — afternoon shade is more useful than morning shade. In fertile soil, arugula grows fast and produces large, mild leaves. In poor or dry soil, it grows more slowly, and the leaves tend to be smaller and sharper in flavor. Keep the soil consistently moist; drought stress intensifies the peppery compounds.

Bolting is the defining failure mode, and it comes fast. A week of temperatures consistently above 70 degrees — or several nights above 65 — is often enough to trigger a flowering stalk. Once the central stalk begins to elongate, the leaves narrow and the flavor becomes unpleasantly hot and bitter. Cut the entire plant at the base as soon as you notice the center pushing up. The plant may push out a few usable small leaves from side shoots, but the main harvest is over.

Wild arugula — sold as Sylvetta — is a different species, Diplotaxis tenuifolia, slower to mature but dramatically slower to bolt. The leaves are smaller, more deeply lobed, and have a stronger, more complex peppery flavor. It is a perennial in mild climates. For a longer harvest window in spring, Sylvetta is more forgiving. Apollo is a fast, mild-flavored cultivar of standard arugula, good for baby leaf production. Astro is widely available and performs reliably in home gardens.