Winter Seed Starting

Even though it’s the middle of winter, it’s the season for seed starting! As long as you have room in your home (and enough sunlight or grow lights) then you’ll almost always benefit from starting seeds indoors.

Why Start Seeds Indoors?

For those vegetables that take a long time to mature, winter seed starting gives them a head start. Even for fast-growing vegetables, starting the seeds indoors and transplanting them will reduce their time-in-the-garden and allow you to get more harvests from the same place in your garden through succession planting.

Which Seeds Should You Start Indoors?

When starting seeds indoors, it’s important to know which vegetables do better when transplanted versus being direct-seeded into your gardens.

  • In cooler climates, any vegetables that require more than 90 days to reach maturity will benefit from being started indoors. This includes eggplants, broccoli, cabbage, cauliflower, kale, leeks, onions, peppers, and tomatoes.
  • Any plants that have delicate roots (typically those in the legume family) or that have long taproots (including carrots and sunflowers) prefer to be direct-seeded into your garden as their roots do not like being disturbed.
  • For all other plants, you have the choice of starting them indoors or direct-seeding them into your garden. Usually, the decision revolves around how much space you have indoors.

When Should You Start Seeds Indoors?

The next thing to know is when to start each vegetable plant indoors. This involves knowing a little bit of math:

What date can you plant each vegetable outdoors?

Look on the seed packets and it’s usually based on your region’s last frost date
How many days will it take for a seedling to grow to sufficient size to be transplanted outdoors?

Fast-growing seedlings (such as cucumbers, squash, and tomatoes) can be ready for transplant in as little as 5-6 weeks while other vegetables (such as eggplants, onions, and peppers) are slow to develop and benefit from more time spent growing indoors.

For ease of planning, here are some rules of thumb that we use for starting seeds.

Week of:Vegetables to Start Indoors:
February 21Onions, shallots, leeks
February 28Peppers, eggplants, perennials
March 14Brassicas (broccoli, cabbage, kale, etc.), scallions, lettuce/chard (round1)
March 21Parsley, cilantro, dill
March 28Tomatoes, basil
April 4Lettuce/chard (round 2), edible flowers
April 11Squash, cucumbers, melons, other fast-growing vining plants

What are the Steps to Start Seeds Indoors?

Collage of steps to seed onions, including placing seeds in seed-starting mix, tamping them down, adding vermiculite, watering, and placing under grow light

Here are the steps to start your earliest seeds:

For onions, shallots, and leeks there are two options:

Use 1” or 1.25” cell trays. Fill each cell with a damp seed-starting mix (or use a potting mix but then be careful not to overwater) and press 2-3 seeds into the soil. Be sure to push out any large air pockets in the soil. Cover each cell with vermiculite and once again press down to create contact between seed and soil.

Or you can use larger cells to start seeds together and later tease them apart when transplanting. Place approximately 30 onion seeds along the top of the soil in a 4” plant pot and then cover it with vermiculite and press down to ensure contact between seed and soil.

For peppers, eggplants, and perennials:

Plant them into 1” or 1.25” cells. Aim to bury the seeds by approximately 1-2mm (not any deeper) and cover lightly with vermiculite to retain water in the soil while still allowing sunlight to reach any foliage that emerges through the vermiculite.
Check the soil regularly to keep it damp (never sopping wet) until seedlings have germinated and established.
Once the seeds have germinated and the initial leaves have emerged, allow the soil to dry slightly between waterings, place in maximum light and remove the humidity dome (if you used one – domes are not necessary when using vermiculite).

We’ll talk more about seedling care in future editions of our newsletter.