The answer to “when can I start seeds for my spring garden” depends a lot on how much of a gambler you are. If you have seeds, seed-starting materials, and space with lighting galore, then anytime is probably a good time.
If, like me, you have limited space, lighting, and materials, following a more conservative schedule may be a better choice.
For spring veggies and early flowers, my first planting usually begins in mid-to late February. That is when I plant seeds for English peas (and sugar-snaps), spinach, dill, and early flowers like larkspur outdoors in the garden. That is also usually when I set some seed potatoes in a single layer in a lighted space indoors (sunny window can work) so they begin to sprout for mid-March planting.
The problem with planting earlier is that some seeds, peas especially, will rot in the ground if they are too cold and damp for too long. When they do come up, though, they can survive some very cold weather. So can little spinach seedlings. The dill and larkspur won’t come up until later, but they do better when planted early outdoors. That is just their way.
Seeds for other spring crops may come up in a stretch of warmish weather if planted outside very early, but if we get a return to actual winter, with temperatures dropping below 20 degrees F for more than a couple of hours, the little seedlings are not likely to survive. Spinach seedlings can take the cold, and it is possible that kale and collards can, too, but lettuces are less happy with such very cold nights, and new carrot seedlings might not make it, either.
Since the weather can still turn very cold in February, I keep an eye on the forecasts before planting even the most cold-hardy of veggies outside.
For most of my spring veggies, I wait until the first of March to start seeds indoors. That list usually includes lettuces, parsley, and beets. When these little plants are big enough, I move them outside for a few hours each day to help them adjust to life out-of-doors before transplanting them into the garden. By the end of March, they should be ready for that move.
Seeds for peppers often are slow to come up, and I tend to start some peppers, for summer, in the first or second week of March, too. Carrots can be planted outside at around the same time.
Tomatoes are a lot speedier to develop than peppers, so I tend to wait an extra week or two before starting any of those.
(Photo at top is of basil seedlings, started as seeds at the end of March, 2016, for sharing in May with other gardeners. Photo by Amygwh.)