Seed or Start?

[AZGardener]

Hey guys- This year I was very quick when it came to my onions bc the tomatoes and my kids took priority Next season I am going to give the onions a serious go. What's better, starting by seed or by start? Where do you get your starts or seeds? Online or from the box store?

I planted a good 80+ by start BUT they look very wimpy? They are all tucked between the tomatoes and I'm not sure what the key is for these guys? Since I water my tomatoes every couple days, do they need more watering? Some look very perky but many look very limp and are falling over (the greens that is). Just trying to get some advice before fall ordering. I'm going to give garlic a try too... Hoping for garlic and onions next spring! Thanks!