Kale growing in the snow.
Credit: Sarah Crowley

Now Is the Best Time to Grow Your Own Leafy Greens — Here’s Everything You Need to Know

updated Jan 8, 2021
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Hot summer days spent in the garden are now, undoubtably, distant memories, as we kick off the first week of January. Now the days are cold and dark. But that doesn’t mean we have to stop gardening completely. In fact, many leafy greens actually thrive in cold climates — especially in the winter. It’s true. And they’re often better in the winner.

While leafy greens are often planted in the fall or spring (to ensure the plant gets established by growing roots and adapting to its environment), a cold spell or frost will make the leaves taste noticeably sweeter. It’s science, but simply put, the starch in the leaves turn into sugar. Hence, the sweetness.

Want to start a leafy green garden in the middle of January? Here’s what you need to know — and the four greens you should grow.

Credit: Sarah Crowley

First, 5 Key Tips for Growing Leafy Greens in the Winter

1. Pick between seeds versus seedlings.

Deciding whether to start your garden with seeds or seedlings is about convenience, preference, and time. Seed packets can easily be purchased online and are usually available in a wide selection of varieties that you might not find in your local supermarket. Seeds allow you to participate in the entire growing process, from germination to harvest, but take more time. Seedlings give you a head start by a few weeks and cut out all the wondering if the seeds will sprout or the worrying about delays. The cons with seedlings is that you’ll have fewer options and might want to stick to buying them from local nurseries.

2. No matter what, start things off inside.

Seeds need plenty of warmth to germinate, so at this point in the year, you’ll likely need to sow seeds in pots indoors. But that’s easy! Choose an area that receives plenty of sunlight, ideally a west- or south-facing window with ample air circulation. And keep reading the rest of this story.

Note: If you’re in a place with a warmer climate, you may be able to sow your seeds outside right now. The temperature needs to be a minimum of 40°F, although most leafy greens seeds prefer warmer weather to sprout. We provide info throughout this story, should you want to start seeds outside.

If you’re using starts, replant them in spacious pots about 12 inches deep (so the roots have enough space) and eight to 12 inches wide (so the leafy green has enough room to grow and expand). Keep them inside for at least a couple of weeks to a month as the seedlings adapt to their new home. 

Credit: Sarah Crowley

3. Choose big containers that you can carry.

You’ll want to sow seeds or plant starts in spacious containers, so they have room to grow to their full size. This way, the plant can establish itself without having to be replanted, which calls for the plant to adapt to a new home and can be stressful. Arugula, for example, doesn’t like to be transplanted and doing so can delay the growth process — so plant seeds in a spacious container from the get go. You can plant a bunch of seeds in one big container or spread them out in several pots. Just make sure the containers are fairly deep, at least 12 inches tall, so that the roots will have room to grow. And that you can carry the container (see below).

4. Bring your plant outside, when it’s ready.

Once your plant is settled (it should be about nine to 12 inches tall with at least four leaves), it can handle colder temperatures and you can place the pot outside to chill and sweeten up. Consider placing the pot near a wall or covering the pot with a tarp to protect the plants from the direct harshness of the elements (wind! Rain! Snow!) Growth may slow down a bit, due to the colder temperatures, but that’s okay!

5. Know that 28 is the magic number.

Once the plants are well-adapted to their pot and are a decent size, you can place them outside as long as the temperatures stay around 28 degrees and above. There’s no need to bring them back inside unless temperatures are going to plummet or you prefer them indoors. 

It’s a good idea to bring the plants inside when temperatures dip lower than 28 degrees. If you don’t want to stay tuned to the weather report and temperatures are supposed to drop below, you can bring them back inside to avoid moving the plants back and forth. Once exposed to even just one cold frost, the leaves will be sweeter.

Credit: Sarah Crowley

4 Leafy Greens to Grow During the Winter

Here are four leafy greens that can handle a hard frost, which is around 28°F.

1. Arugula

Arugula has dark green leaves with a pungent and peppery flavor. There are many types to choose from and leaves can be long, spiky, or rounded.

  • Soil: Plant in loose, well-drained, and fertile soil with a natural fertilizer, such as humus or compost. 
  • Sunlight: Arugula does best in full sun, ideally a minimum of six hours and more is better. If growing indoors, place the container near a window with lots of direct sun.  
  • Spacing: Sow six seeds about every six inches. Once the plant is 1/2-inch tall, you can thin down to one every six inches.
  • Germination: The soil temperature needs to be at least 40°F for seeds to sprout but does best when the temperature is between 50 and 70°F. You can add mulch to maintain warmth in the soil.  
  • Water: Arugula likes moist soil so you’ll want to water frequently, but make sure you don’t over-water by soaking the soil.  
  • When to harvest: You can pick baby leaves within a month of sowing seeds; for mature leaves, wait until the six-week to two-month mark. 
  • How to harvest: Pick leaves when they are two to four inches long. You can snip with scissors at the base of the stem. Leaves will usually re-sprout a couple more times.  

2. Kale

Kale is part of the Brassica family and is a type of cabbage that doesn’t form a head. The most well-known varieties are lacinato kale, also referred to as dinosaur kale for its slender, bumpy leaves; Red Russian with flat, green oak-shaped leaves and purple stems; and curly kale with dark-green, frilly leaves. 

  • Soil: Kale needs rich, well-drained soil with plenty of organic matter, such as compost, which provides plenty of nitrogen to the plant for healthy growth. 
  • Sunlight: Place containers in an area where there is a minimum of six hours of sunlight a day, ideally longer if possible. 
  • Spacing: Once sprouted, thin seedlings so they are eight to 12 inches apart. If you’re planting seedlings, space them 18 inches to two feet apart.  
  • Germination: 65 to 85°F is the ideal temperature for these seeds to sprout. 
  • Water: Water often to keep the soil moist but not saturated. 
  • When to harvest: You can begin harvesting within 30 to 60 days, depending on the variety and if you prefer baby leaves or fully mature ones. When temperatures go below 20°F, the plant will often go dormant until the weather warms up again. 
  • How to harvest: Harvest under or around a third of the plant at a time to ensure healthy growth. Typically, kale will sprout new leaves too.
Credit: Lauren David

3. Spinach

Spinach is similar to beets (and both are part of the Amaranth family). There are many types of spinach to choose from — small, tender baby leaves to bumpy and pointed leaves. 

  • Soil: Spinach likes fertile, rich soil that is amended with a natural fertilizer, such as compost.
  • Sun: Place receptacles in full sun. 
  • Spacing: Place seeds about 3/4 inch apart. Thinning the plants as they grow won’t be necessary.
  • Germination: If you want to sow outside, make sure the temperature is above 40°F, although 50 to 75°F is ideal. 
  • Water: Keep the soil moist by watering a few times a week, but take care to not saturate the plants.
  • When to harvest: Leaves are ready for picking between one to two months, depending on the variety. 
  • How to harvest: Pick outer leaves first and leave 1/2 inch on the stem. The leaves usually regenerate, so you may have a second harvest. 

4. Swiss Chard

Swiss chard is a hardy leafy vegetable with long, savoyed leaves and is part of the Amaranth family, like beets. If you want color in your garden, opt for rainbow chard with burgundy, pink, orange and white stalks with these hues in the leaves, too. 

  • Soil: Swiss chard thrives in loose, well-drained soil with ample organic matter, such as compost. 
  • Sunlight: Grow in an area where it will receive direct sunlight, preferably for a minimum of six hours a day. 
  • Spacing: Sow two seeds every 8 inches; when the plant is around  1/2-inch tall, you can thin them to one plant per 8 inches.
  • Germination: Swiss chard seeds like it hot! They prefer 75 to 90°F.
  • Water: Chard does best when the soil is kept moist, so watering frequently is ideal. However, be sure to not over-water the plant to the point where the soil is soggy. 
  • When to harvest: Leaves are mature around the two-month mark. If you want milder and smaller leaves, you can pick them after a month. 
  • How to harvest: Choose outer leaves that are around 6 inches long and cut them about an inch above the soil line.