Q.root rot in onion seedlings
Golden Globe onion seedlings were planted in a raised bed in early April. After a slow start onions appeared stunted. On lifting plants roots were reduced to about half inch, with none with longer root. soil was kept moist but not wet or drenched. What is cause and cure.
You may have chosen a variety that's not perfectly happy in your USDA Zone, so first make sure you have the correct cultivar for your area. There are also two main "strains" of onion that get planted in spring or fall. If you have the right one(s), next check the spacing and phosphorus content of your soil. If all of these factors are in line, there's a chance that if you've had a long stretch of weather where the temperature has been consistently below 70 degrees, that could be the cause of your roots not taking hold and producing onion bulbs. This article may help you:
https://www.gardeningknowhow.com/edible/vegetables/onion/find-how-to-grow-onions-in-your-garden.htm