March and April are what we call the “cool season” when it comes to veggies. Typically that means planting vegetables either for their roots, such as onions, potatoes or carrots, or for their shoots (think leaves), such as lettuce, cabbage and spinach but also broccoli and cauliflower. Warm season veggies are like tomatoes, peppers, beans and squash and they are planted later when the soils get much warmer. Today I want to focus on onions.
First, it is important to understand how an onion grows. It is what we call a biennial which is a plant that grows vegetatively one season, then goes to seed and dies the second season. So if you were to plant your onions from seed this year and left them in the ground over the winter they would form a bulb the next summer and then go to seed and die. When an onion goes to seed it will rob energy from the bulb and you end up with more or less a hollow bulb. More about that later.
Onions can be planted from seed, transplants, or sets. You can find all three available this time of year. Let’s talk about the differences.
Sets come in mesh bags and look like miniature onions. These are essentially onions that were grown last year from seed and then harvested at the end of the season. When I plant sets I space them only a few inches apart so I can eat green onions as I thin them. It only takes about 4 weeks from the time you plant a set to the time you can start eating green onions. The remaining plants will continue to grow and eventually form a nice-sized bulb but beware, sets often go to seed (because it is their second year) so plan on breaking off the flower stalks and it will help stop the process. Sets usually work great for onions that you want to store. Some varieties to look for are White Snowball, Yellow Stuttgarter, Red Karmen, and Sweet (a generic sweet variety).
Transplants are also plants that were started late the previous year but they are much younger and rarely go to seed as readily as sets. Again, I plant them close at the start but eventually allow 6 inches between them as they mature. Walla Walla, Red Wing, and Yellow Candy (my new favorite onion) all come as transplants and are sweet varieties that are good for fresh eating but don’t store very well.
You can also buy packets of onion seeds but it will take two years for them to form bulbs. If you just want green bunching onions then seeds are the best way to go.
Onions are heavy feeders so be sure and incorporate plenty of compost and a good balanced organic fertilizer at the time of planting. Like all veggies, the richer the soil the bigger the harvest.
When your onions start to dry up break off any flower stalks, stop watering and let them harden off in the sun for a couple of weeks. After that you can clean them up and store them in a cool dry place so you can enjoy home grown onions for several months. It’s just that easy.