While many veggies like tomato and melon grow best in summer, there are quite a few that grow best in cooler weather. There are also some that have such long days to maturity that they are also started very early.
There are many blogs out there that are general for the whole country, but it is helpful to know the dates to start seeds according to your zone and area. To do so, you need to know the average last frost date. The average last frost date for the Treasure Valley is around May 9th. If you are in a different location, you can also use that link to calculate your last frost date.
Knowing this frost date, you can use the days to maturity and number of weeks to seed ahead of that to calculate exactly when to start each seed. The information is the same for vegetables and flowers.
Having already calculated many plants, here is a veggie cheat sheet!
With a long seed-lead time, there are a few seeds that can be started in mid-late January.
Onion and leek: Seed January through February. They are generally seeded 8-12 weeks before planning out, so if planting them out at the recommended time of 2 weeks before last frost (around 4/25), you would seed them on 1/30-2/27. They can be planted once the ground is unfrozen but the general rule is when they have three leaves. I’ve seeded them earlier in Jan by growing them in milk jugs outside, but you can also seed them through February. Just note that they are very slow growing, prefer cooler weather, and have a single harvest from June through July. When it starts to get really hot, the leaves on top turn yellow and fall over; after that happens, you know they are ready to harvest. I’ve found that onions are one of the most satisfying vegetables to grow. You can store them in cool, dark storage for awhile.
Parsley: Seed January through February. They are seeded 8-12 weeks before planning out, so if planting them out at the recommended time of 4 weeks before last frost (around 4/11), you would seed them on 1/16-2/13. They can be planted once the ground is unfrozen but may need to be covered if it gets really cold. They tolerate a light freeze well (29-32 degrees), and also do well in the summer. Tip: harvest them as a bunch and put the stalks in water in the fridge. I haven’t done it yet, but I plan to dry my leftover parsley as well for winter use.
Oregano: Seed late January-mid-February. I’ve seen a vast variety of advice on when to seed these, but in my own experience, they grow very slowly and are hard to germinate. Sprinkling the seeds on a 4” pot seems to work better than seeding them in flats. Seeding them in January through February should work fine.
Thyme: Seed 8-10 weeks (2/13-2/27) before transplanting out before last frost (4/25). They are rather slow germinating, so many people buy transplants. They are native to the Mediterranean and thrive in full sun, and I have found no problem with growing them in the Treasure Valley. At the end of the season, leave them in the garden – since they are cold hardy down to zone 5, they may act as a perennial and grow back each year. It is fun to experiment and see what does grow back each year. I keep thyme in my garden with my flowers on a drip system and it grows all summer. In the fall this past year, I harvested it all, washed and dried it, picked the leaves off and bottled it as a dried herb. Far better than freezing it, this is what I plan to do each year from now on.
Broccoli: They are seeded 7-10 weeks before planting out, in late February through March. If planting them out at the recommended time of 2 weeks before last frost (around 4/25), you would seed them from 2/13-3/6 but I’ve seen them seeded earlier in January. They tolerate a light freeze well (29-32 degrees), but do not do well in the summer. They grow best in spring and cooler fall, so the earlier you can seed and plant these, the better success you will have in growing them. If you wait to plant these until May, you likely won’t get much broccoli as they prefer cool temps and the heat stresses them.
Celery: Seed in February. They are seeded 10-12 weeks before planning out. They can be transplanted up to two weeks before the last frost (around 4/25), you would seed them from 1/30-2/15. They tolerate a light freeze well (29-32 degrees), and also do fine in the summer. You can harvest single stalks throughout the summer, or whole heads all at once. They are extremely slow growing and if you grow them, I would recommend just a few heads. I grew 8 two years ago and still have chopped, frozen celery in my freezer because the heads weren’t ready to harvest until the end of the season.
Direct Seed (Outdoors)
The direct-seeded veggies all grow quickly, around 3-6 weeks from the time you seed them. They grow well in cooler temps and do not like hot weather, so the earlier you can seed them, the better as they will die out once the weather gets too hot. The first year I planted these, I thought I was a failure when they died because I didn’t know they didn’t tolerate heat well. Know it’s not you, it’s their temperament! You can direct seed them once the ground is workable (not frozen), or you could also start the seeds indoors. Direct seeding could happen in February, but might be later depending on how cold the winter has been. If the ground is frozen, seed them in February and plant them out in late February or m any time through late spring. For a continuous harvest, both also do well as successions, meaning you can seed them every two weeks for 4-6 weeks and get a smaller harvest throughout the spring instead of all at once.
Peas: From snap peas, to shell peas, to snow peas, all can be seeded right in the ground for best results because they thrive in cooler weather. They can also be started inside however since they are fine with being transplanted. A big aha for me in looking at the cooking magazines and blogs is - the reason spring dishes have peas in them is because they are a cool weather plant! At our house, we typically like to eat them off the vine. It should be noted that if you grow any type of pea, they need some sort of trellis because they are vining plants.
Lettuce: With the ease of buying lettuce in the grocery store, it is tempting not to grow lettuce. However, since it is so easy to grow, it is so satisfying! It is also very prolific, so just planting a small amount will do the trick. This one is a great candidate for succession planting so you don’t get an overwhelming amount of lettuce at once. I found that seeding around 1-2 feet at a time was a good amount of lettuce leaves. It is great to grow a variety of lettuce though, from spinach, to lettuce heads. There are a ton of different varieties so it is fun to see what you like. Lettuce leaves like spinach and spring mixes grow quicker than heads of lettuce.