Christian, do you know if you planted short day, intermediate day, or long day onions?

You will have better luck with onion plants (seedlings) than with the little bulbs in the net bags. The short day varieties 1015Y and white granex are two varieties recommended by Texas A&M for the north Texas climate. The plants are usually available at garden centers starting around mid-January thru mid-March and are normally sold in bundles of 40-60 plants depending on size. And you did plant at the right time. Here's a link that has lot's of onion growing information: http://www.dixondalefarms.com/

Don't expect to grow good sized onions from bulbs because they are second year that will go to seed. Water is very important because they have shallow roots. They need constant supply of moisture and nitrogen

Thanks for the good advice everyone. I'll try the plants next year instead of the sets.

You can also try seed if you like starting from seed. I'm not sure when to start short-day onion seeds, though...I grow intermediate and Long day here.

Short day onions are seeded in September. If transplanting in January -February, the intermediates will do better. Short day onions do best overwintered as they need to get some plant growth before they start bulbing in March.

Christian- I had a similar problem here in SoCal. I planted onion sets (white) last fall that I had purchased from a nursery, and then planted bulbs (red) purchased from Home Depot in Feb of this year. More than 2/3 of white onion sets bolted, whereas most of the red onion bulbs did not grow very much. Due to failure, I did some research and learned about short, intermediate, and long day onions. I suspect that the reason why so many of my white onion sets bolted is due to SoCal weather. When I planted them last fall, they grew extremely well, but then in Jan-March we had some cold days, and then got warm again, so that essentially made the onions go through two growing seasons causing them to bolt. My theory as to why the red onion bulbs failed is due to the bulbs being either an intermediate or more likely as digdirt pointed out was a long day variety.

So, already I purchased short day variety seeds that I will plant in the fall, specifically Red Creole and Texas 1015 Supersweet, and am hoping that I can get a nice harvest next year.

Definitely agree, go with plants, not sets. IMHO, sets are good for green onions, but not for larger keeping onions. importance of even moisture can't be stressed enough with onions.