Greens and onions go together like a perfect pair. Greens like spinach come on for a few weeks, then they're gone. Plant the onions in between the spinach. So when the spinach is done growing, it's the onions turn to take over and grow in that space. They'll take over and you'll have 2 crops for the space of one!
 
This 4-pack include:
2 Spinach plugs (with about 3 spinach in each). 
2 Onions (red + yellow) sets: eat fresh as they are growing or harvest in August for storage