Speedy
Arugula in the US

Arugula is a cool season crop, so you want to get it started when it's not too hot, you know. Direct sow your seeds about half an inch deep, aiming for an inch apart in the row. Once they're up and growing, thin them out to give each plant about 4 to 6 inches of space. For folks in USDA zones 3-5, that means getting your seeds in from April through August, depending on your specific zone. Zones 6-7 can start in March or even February, going into September or October. Down in zones 8-10, you've got a much longer window, from January right through to May, then picking up again from September to December. Like I say, it's pretty quick, so do a small batch every couple of weeks for a steady supply.

Most arugula varieties are happy being direct sown, so you don't usually need to mess about with plug plants. If you do start some indoors for an early batch, just be careful when you transplant them out to avoid root disturbance. Give them enough room to grow and they'll be grand. It's a versatile plant, so it'll do well in containers too if you're a bit short on space, say on a patio or balcony.