We’re all itching to get started sowing vegetable and flower seeds indoors to have transplants ready for our gardens this spring, but most vegetables and flowers shouldn’t be sown for a few months yet. However, there are a few exceptions. Onions, both bunching and bulb varieties, as well as leeks are easy and fun to grow from seed, and sown indoors in late January or early February will give them time to develop into strong seedlings that can be transplanted outdoors in late March or early April. They are tough
vegetables, tolerating late frosts.
Onions and leeks can be planted densely in a pot, with no need to plant in individual cell trays. I sow a whole seed packet in an 8” pot, using potting mix. I cover the pot with plastic wrap after watering well. They will sprout in about a week when they should be uncovered. As soon as they are a few inches tall, every time I water, I fertilize with a very dilute solution of balanced, soluble plant food. Provide good light either on a sunny window, but better under lights, (I use inexpensive LED shop lights.) and it’s advisable to use a fan to keep the air moving (I have my fan on a timer to run every 30 minutes for 10 minutes.)
In just a few weeks, you will have what looks like a pot of grass, but resist the urge to thin or transplant into cells or small pots. They will be just fine until they are transplanted outdoors, if you provide lots of light and keep them fertilized. I always set my pots of onions outside on days when temps are in the 40s to harden them off, bringing them indoors at night.
When you’re ready to transplant, it’s fine to cut back the foliage to 4’ or 5”. Carefully tease the seedlings apart and space scallion onions two or three to an inch (thin them as you use them). Bulb onions are usually spaced 3” or more.
Early indoor sowing of onions is easy and helps scratch the itch to plant this time of the year.
Happy gardening!