I usually ordered the short day sampler packet. You're gonna get about SIXTY of each variety, so be prepared with your double-wide lot! LOLOL!
The yellows and whites grew to a nice baseball size. The purple (milder) ones grew more flat, and not as big, but the mild flavor has its place in some of my dishes.
When you plant them, make sure to space them at least 4" apart. You can start them off closer (3"), and then pull the in-between ones to use as green onions, and to increase the spacing distance for the ones you leave. Ideally, to get the "big "uns" about 6" inbetween.
Also, onions are heavy feeders! Read up on the nutrients on the Dixondale website. I always confuse whether they want heavy phosphorus or potassium. I think it's phosphorus. In any case, be prepared when you plant out, by mixing up an rich mix with a fair share of organics and P or K. And, you'll need to side dress periodically about every 4-6 weeks.
Don't mind the cold, cause they sure don't! Long as it's not a sustained, hard freeze for 3-4 days in a row, they'll be fine. I threw a cardboard box tent over my Earthboxes, just to keep the wind off them, when we had a couple overnight dips into the 30s.
Finally, you'll need to pull out your barber shears. Early on when they're taking off, they'll get top-heavy with the green stems, and might tend to fall over. TIME FOR A HAIRCUT! I used some scissors and cut them back to about 4". Nice and neat, and gave the bulb roots a chance to anchor into the soil. They grow sitting almost on TOP of the soil, so if you're fighting wind, you might wanna have a wind barrier ready just in case you need it!