With a little preparation and some gardening tools, you can grow onion plants in your garden. Here’s how:
First, decide what kind of onion you want to grow. Green onions and scallions grow like weeds in almost all growing zones, but are not as versatile in the kitchen as bulb onions. However, bulb onions need a temperate growing zone with neither extremely hot nor extremely cold weather. Your planting schedule will vary depending on what growing zone you live in. For warm climates, you’ll want to plant for fall, winter and spring. Farther north you’ll be planting for spring, summer and fall harvests. Some of the most popular garden onions are green onions, scallions, Spanish onions (your “common” grocery store onion), Vidalia and Walla Walla sweet onions, pearl onions (for pickling), and red onions (often used on sandwiches).
Next, buy the seeds, starts or “sets”, and seedlings that you’ll be planting. In some cases you can beg something off a neighbor that has plenty, but otherwise you’ll be looking at seed catalogs like Burpee or Seeds of Change or visiting a local greenhouse. It’s a good idea to visit a large garden supply store or home improvement store, because you’ll need to pick up some gardening tools and soil improvements as well. If you’ve already got a good garden plot then your work will be much easier. However, if you’re starting from scratch, you will want to rent a roto-tiller in order to till the earth in your selected site. A tiller is also a great tool for working in soil improvements such as compost and manure, or mineral additions like bone meal (for phosphorus) or fireplace ashes (for potassium), both of which onions need to grow.
Make sure that you are on schedule for growing in your climate. In most cases this means that if you plan on starting from seed, you will be growing indoors anywhere from a month to three months before you plant outside. For that, you’ll want seedling beds, potting soil, maybe even a grow light. For summer harvest, you start seedlings before the last spring frost, and for fall harvest you start them before the last frost of the year.
Onions thrive in rich, well drained soil, so you’ll want to apply your compost and minerals and then till, till, till. Remove all rocks that you come across. Set the onion seedlings 3-4 inches apart. For sets (bulbs), plant 1 inch deep and 2 inches apart. Keep the plants thinned through the growing season by pulling one up every so often and use the greens in the kitchen as scallions. Keep them weeded! Onions need sun and won’t thrive if they are competing with weeds and other plants, or are too crowded. Remember, a good start is what will determine the eventual bulb size of the onion. Water well on dry days, fertilize with compost or compost tea, and keep the plants well spaced.
Onions have their own particular garden pest – the onion maggot. Prevent an attack of the wormies by covering your crops with row covers. This will keep out the flies and prevent them from laying their eggs that eventually turn into those lovely maggots, eating their way through your hard work. You can purchase row covers at just about any large garden supply store. Once the worms have hit your crops, however, just about the only thing you can do is manually search and destroy by pulling up plants, killing the worms and getting rid of the plant entirely – do NOT compost the plant as it will just introduce the pest to your compost! You can also try such methods as worm traps or beneficial predators (anything from birds to other kids of bugs that eat the bugs you don’t want…in this case, spiders and rove beetles). By far the best offense is a good defense, however. If you plan on growing onions in future years, you will want to practice crop rotation as well, to prevent future infestations as well as to give the soil a chance to rest.