This peppery leafy green has become a kitchen staple and an expected menu item at any self-respecting restaurant. The combination of meaty texture, heat, and spiciness means it can stand up to funky cheeses and balsamic vinegar without hesitation. This description applies to arugula grown in rich soil and not cut before attaining its full complexity of flavors. Mass-produced arugula that is smaller than your pinky and sold in plastic tubs is another thing entirely. Don’t be deterred. You can grow great arugula.
A member of the brassica family, arugula is relatively easy to grow. Direct sow as soon as the soil is workable. Plant four to six seeds per inch into furrows spaced 8 inches apart and cover lightly with soil. Or broadcast seeds over the planting area; the thicker it is sown, the smaller the plants will be, so decide what size leaf you are hoping to achieve and experiment. Thin if needed and eat the thinnings. Sow every 2 to 4 weeks to have a crop all season long. Arugula is a heavy feeder and prefers rich soil; yellow leaves indicate that your garden soil needs nitrogen. All brassica salad greens are susceptible to flea beetles, which devastate the leaves with hundreds of tiny holes. The best defense is to place a row cover over the furrow before germination and pull it tightly along the edges.
The old way to harvest arugula is to let it get quite large, 5 to 7 inches tall, and make bunches with it. It is still occasionally sold this way and arugula that size is great for cooking. The new way is to grow it baby-sized, 2 to 3 inches tall, at which point it tends to be milder. I prefer to split the difference and let it grow to about 4 inches. This size will give you the meaty texture and full flavor and will be great for both cooking and salads.
To harvest, I cut around 1 or 2 inches above the soil, being careful not to cut below the part of the plant from which arugula will re-grow. You can generally cut a patch of arugula once a week for 3 to 4 weeks in the summer, but in the spring and fall it will take longer to regrow. When after a few weeks a patch of arugula becomes a little ratty and the leaves gets tougher, start harvesting from a new patch.
Sylvetta is a wild (perennial) arugula with a strong flavor and uniquely serrated leaves. I recommend growing it only in the spring and summer. My favorite cultivated variety, Astro, has been breed with a reduced desire to flower.