Advice on onions and how to deal with root maggots
April 29, 2021
Most likely many of you gardeners have your garden spaces melted off and some are digging in the soil already. But then some of us still have piles of snow! I encourage you to use the heavier snow accumulation of last winter to give you some information about your site. If your beds are still covered in snow, it probably means that they do not get much light unless there is some other reason for deep snow there. This year much of the melting is coming from sunlight rather than rain so it is a good indicator. Maybe you can do something about getting more light or maybe it is just good info for you to have as you grow your garden. I would also encourage you to observe how the excess water in December affected your site. Maybe you will need to try and change it or maybe enhance it and use the knowledge in your garden planning.
One of the first crops that can go in the ground in the spring is onions. I have found using onion transplants to be the best way to grow onions here. If you start your own, they are easy to grow but you need to start them in February. Most of us buy them from Texas. When you put transplants in the ground bury them only an inch or so, and when they start to bulb up in July don’t cover them. This is a mistake many gardeners make. Onions like to grow on top of the ground with roots near the surface. With shallow roots they need to be kept watered regularly as they get thirsty when the top layer of soil dries out. Don’t get discouraged growing onions here. They enjoy heat so some summers they do really well, and others we must be satisfied with smaller onions. Did you know that an onion bulb is really made of modified leaves so that with more leaves you will get bigger onions. Thirteen leaves is the perfect onion number so you can strive for that! Nutrients, weather and onion variety are all factors in the size. Onions are vulnerable to the onion root maggot fly. Also, the last few years I have been having problems with onion thrips. Their damage shows up as white streaks on the onion leaves. Fabric row covers help protect against both pests and also give a few extra degrees of heat which onions love.
Fabric row covers are a pain! However, the few degrees they provide really does make a difference in the attitude your transplant has about being put into the cool soil early in the season. Often a gardener’s motivation for using row covers is root maggot protection. The general rule, probably based on outdated climate patterns, is that the flies are done laying their eggs here by early July, so that is when you can safely take off the row cover. Besides onions, root maggots will commonly feed on any of the brassicas. They also love turnips and radishes.
I still use fabric to protect my onions and turnips, but for the larger plants that I put out as transplants, I use a different technique. Charlotte Olerud told me about this 15 years ago and I have not had root maggots in my broccoli or cauliflower since. As you put each transplant in the soil take a piece of quilt batting and wrap it directly around the stem. It must be touching the stem. Figure out a way to make it stay there. I use little rocks on top of a plastic cover. The plastic cover is probably overzealous but I really don’t want to lose my transplants. If you use cotton or wool batting, at the end of the season you can just leave it in the soil to decompose. The Root Maggot Fly lays its eggs on or near the stem. The larvae/maggot crawls down to the roots to feed. If your plant looks healthy and one day you go out and it looks droopy for no good reason, likely you have root maggots eating the roots. Pull up the plant and you may find little white maggots about a quarter-inch long. Try to get them all out of your bed and dispose of that soil away from your garden. If the plant is big enough, with more roots, it can often survive an attack with just reduced production. You will have to decide if you want to let the plant live and leave the root maggots in the soil or pull it. It’s one of many hard decisions a gardener has to make! I have had some success waiting to plant fast growing turnips and radishes until mid-July to avoid the root maggot problem.