Bulbs Abound: Planting Onions in Winter
Some freshly harvested large yellow onions.
Happy new year, plant nerds! With the excitement of plotting your spring gardens on the horizon, what is there to in the meantime? Although January is not the most active planting month of the year, now is the time when we can start planning and planting our onion bulbs! Whether you live in foggy San Francisco or sunny Danville, now is the time to get your onions in the garden.
Onion bulbs growing and developing in the soil.
Onions are an essential vegetable staple in almost every food culture and are such a great crop to include in your home garden. With many varieties of tastes and colors, planting onions in the garden is absolutely a dealer’s choice. If you plan on growing a large amount of onions to keep them long-term through winter, you can choose storage-type varieties. If you plan on using them immediately after harvest, plant day-neutral varieties. Whatever your onion needs are, there is a variety out there for you. Check out some large onion varieties here.
There are a wide variety of onions that each offer different flavor profiles and colors.
Before planting your onions in the garden, make sure to amend your soil with organic matter to provide the best possible conditions for your onions to flourish. If your soil is too sandy or clayey, add some lovely compost, worm castings, or manure so it can develop the correct consistency for planting (for more information on amending soil, check out my soil blog post here.)
Here is a onion bulb set bought from a nursery.
Plant the bulbs pointy side up in the soil.
The easiest and most common way to plant onions is by purchasing onion bulb sets from a local nursery. You can, of course, plant your own (or purchased) seedlings, but if you have never grown onions before, I recommend getting a set. Although there have been some mild successes in planting sprouted grocery store-bought onions, I would avoid these altogether. They tend to seed immediately, yield poor results and could carry disease. With your onion bulb set, take each bulb, plant the pointy side up just beneath the soil surface, and space them around four inches apart. Make sure they are in full sun.
Harvesting an onion while it is still young will give you lovely green onions but a tiny bulb.
When planting your onion bulbs, fertilize them right away, either with a vegetable-specific fertilizer or an all-purpose plant fertilizer. Feed them a lot of water in the first few weeks and watch out for competing weeds. When you plant bulb sets in January or February, they will grow large above the soil surface before the bulb begins to develop their form. Make sure you don’t pull a bulb out come spring because it has a lot of gorgeous growth on top. After all, the bulbs take a lot longer to form than the foliage. While the bulbs continue to grow, feel free to harvest some green onion stems from your plants for consumption, it won’t hurt the bulb to trim one or two off the top of the plant.
Freshly harvested gorgeous red onions.
Lastly, remember to choose your varieties carefully. Only plant onion varieties that have proven to grow well in your region, and if you buy a bulb set, make sure to plant them in January of February. Planting onions in March or April will usually result in small bulbs or poor growth because onions are sensitive to day-length. If they don’t have enough time to grow once the weather starts warming up and the days get longer, they won’t grow as big as they could have if planted as early as possible. A couple of varieties I’ve worked with in the Bay Area include ‘Yellow Sweet Spanish’, ‘Walla Walla Sweet’, ‘Fresno Red’, and ‘Superstar F1’. Talk to your local nursery about the varieties they have, what kind of onions you want to grow, and whether or not you are growing onions for storage or immediate use. Happy bulb-ing!