Don’t Make These 11 Winter Sowing Mistakes This Season

Beat the cold with winter sowing! This method takes advantage of natural outdoor temperatures and common household items, making it perfect for beginner and experienced gardeners alike. Seasoned grower Jerad Bryant shares 11 mistakes you’ll want to avoid while sowing seeds in the winter.

Top view of plastic bottles used for winter sowing of seeds in January, filled with soil and small sprouted green seedlings that shows winter sowing mistakes

Contents

Winter seed sowing can mean one of three things. A relatively new method involves gathering old milk jugs and plastic containers before modifying them to grow vegetable, flower, and herb seedlings while snow falls. This works best for plant seeds that need slightly warmer temperatures than those your climate offers. 

One other winter sowing method works best for native plants that thrive in your local region. Many native annuals and perennials require cold stratification before they sprout. Cold stratification is a necessary process some seeds undergo; they need many weeks with cold temperatures. Native seeds often require it, as they evolved to withstand harsh conditions in their habitat. 

The final winter sowing technique is for warm-climate gardeners who want to grow cool-loving plants. Some regions in Florida, Southern California, and Nevada are frost-free. During the coolest months, sow veggies like broccoli, fava beans, and spinach or herbs like thyme, lavender, and catnip. 

No matter how you’re winter sowing, you’ll want to avoid the 11 common mistakes listed below. Thwart diseases, pests, and problems with expert care, and consider boosts from these products to help alleviate issues:

Urban Worm Coco Coir

Urban Worm Coco Coir

Our Rating

Urban Worm Coco Coir

Urban Worm Company Worm Castings

Urban Worm Company Worm Castings

Our Rating

Urban Worm Company Worm Castings

Mineral Boost: Azomite Powder

Mineral Boost Azomite Powder

Our Rating

Mineral Boost: Azomite Powder

Ignoring Your Climate

A shot of a germination tray with a cover to maintain humidity in a well lit area
Provide the seedlings extra protection in case of unexpected weather.

Winter sowing differs depending on where you live; the longer your winter is, the later you’ll want to sow seeds. Growers in USDA hardiness zone 8 will sow broccoli in early April, while those in zone 5 will do the same in late April through May. This is one example, though many other crops work similarly with staggered planting times.

USDA hardiness zones are one way to determine when to plant seeds, though first and last frost dates are another. They tell you when to expect the last frost in spring and the first one in autumn. Most seeds have a rating on their packet that tells you when to sow them according to frost dates. 

Although estimations are excellent techniques for determining when to start seeds, they aren’t perfect! Late frosts, random storms, and excess rainfall may spell disaster for your sowing plans. Grant your seedlings extra protection so they’re safe in case of unexpected weather. Cover them with humidity domes or similar structures to keep them slightly warmer than the outdoors.

Using the Wrong Seeds

A shot of several packets of seed with its contents spilled on dark soil ground in a well lit area
Select plants that require cold stratification.

Winter sowing is best for plants that need cold stratification or those that germinate at low temperatures, and it is usually a mistake to use this method for warm-weather crops. Broccoli and parsley, though they love cool weather, need warm temperatures to germinate. Peppers, eggplants, tomatoes, onions, and lettuce will sprout quicker if you start them indoors in pots with a warm environment.

So, when do you want to winter sow? December, January, and February are the perfect months to set out the following plant seeds in milk jugs:

VegetablesHerbsOrnamental Species
SpinachOreganoNative trees
KaleParsleyNative plants and vines
Brussels SproutsCatmintHellebores

Native plants may benefit from the milk jug method, though it’s not essential for their success. They grow well with what nature provides them! Sow them outdoors where you want them to thrive in your garden. You can direct sow species like milkweed, blazing star, and blue grama grass.

Planting Too Early

Close-up of six plastic jugs cut in half as small greenhouses, filled with soil and seeds.
Planting seeds early can expose them to unnecessarily warm temperatures.

One of the biggest winter sowing mistakes is starting too early. If you plant seeds too early, and you’ll subject them to unnecessarily warm temperatures. Milk jugs or humidity domes trap heat, making their inside air and soil slightly warmer than the outdoors. This means the seeds may reach optimal germination temperatures and sprout early. They’ll then have to withstand recurring harsh frosts as sensitive seedlings. 

Wait until temperatures are cool after your first average frost date in fall. December, January, and February are optimal months for sowing in jugs or containers. These months rarely have warm days, meaning seedlings will stay dormant until spring begins arriving.

Planting Too Late

Rows of several jugs used as domes during the cold season
Starting too late can affect seeds that require cold stratification.

Planting too late is another common winter sowing mistake! This affects seeds that require cold stratification the most, as they must undergo frosty weather to germinate. In the same way that garlic, tulips, and daffodils need harsh winters to perform in spring, many native plants need many frosty weeks before they can sprout. 

Don’t worry if you planted crops like spinach and kale late, as they’ll still sprout with cool weather that’s common in spring. Simply remove their covers so they don’t overheat as sunshine and warm temperatures increase during the growing season.

If you waited too long to plant seeds requiring cold stratification, you may place them in your refrigerator instead. This creates a false winter, convincing the young plants to grow and thrive once you take them out and plant them. Place the seeds in a container with a moist paper towel, then situate them in the fridge for as long as they need. 

Overseeding

An overhead shot of a pot with piles of seeds and soil in a well lit area
Follow guidelines on the packets for proper spacing.

As you’re planting, you’ll want to follow the guidelines on the seed packets for proper spacing. Some seeds like crowded conditions, while others prefer space to grow well. Others, like onions, differ in spacing requirements depending on what crop you’re trying to grow—green onions need little space, while bulbing and scallion types require some distance to bulb up. 

Some crops inevitably overseed, like beets and Swiss chard. Their seeds are clusters, which means a single one will grow into two or more seedlings. If you overseed accidentally or are growing beets and Swiss chard, you’ll want to thin the seedlings after they germinate. This allows them to develop strong, resilient root systems.

To thin seedlings, pluck them so a few evenly spaced ones remain. Ensure the remaining ones stay strong and tall, and take care not to damage them while you remove the others. These small veggie sprouts are edible! Throw the extras on salads or sandwiches for a fresh crunch with every bite. 

Forgetting Drainage

A shot of two black pots with drainage holes that is placed on a marble surface in a well lit area
Proper drainage is a key component in container growing.

Lack of drainage is a detrimental mistake when winter sowing in milk jugs and containers. Without drainage holes, containers hold standing water. The water threatens sensitive plant roots, causing root rot and other pesky issues. First, make sure your pots have a few small holes in them before putting soil and seeds inside. 

Most seed-starting containers already have drainage holes, though milk jugs and plastic containers do not. Use a knife to stab small holes into the bottom, leaving most of the surface intact. Other good tools for punching holes include drills and hot glue guns without glue. A glueless glue gun has a hot tip that melts a hole in the plastic! 

Insufficient Ventilation

Close-up, top view of white reusable plastic milk jugs used as pots for winter seed sowing.
Proper airflow is essential for developing healthy plants.

Like drainage, proper airflow is essential for growing strong, healthy plants. Milk jugs already have ventilation because their spouts act as airflow ports. Simply remove the lid to ensure moisture and air travels in and out of the spout. 

Other containers with lids may require some hole punching to work well. Use a sharp knife, a glueless glue gun, or a drill to make holes in the plastic tops. 

Humidity domes often already have ventilation in them. Some have rotating holes that open and close, while others have static holes throughout. If they don’t have ventilation, take them off of the containers once or twice a day to give your seedlings fresh airflow.

Soggy, Dense Soil

Close up of male hands mixing Coconut coir with soil in a large blue bucket.
Avoid soggy soil by mixing a well-draining potting mix with drainage components.

Proper drainage helps avoid soggy soil, though the type of mix you use is the most important part. Most seeds prefer a well-draining mix with some nutrients. Any seed-starting blend will work well, especially if it has drainage components like perlite or vermiculite.

You may also make a soil mix yourself with some basic ingredients. A good peat moss-free recipe comes from Epic Gardening founder Kevin Espiritu and the garden hermit Jacques Lyakov! They use this ratio for starting plants in their gardens, and you can use it in yours. Here it is:

  • ⅓ Pumice
  • ⅓ Coco Coir
  • ⅓ Compost, worm castings, and Azomite
YouTube video

This ratio ensures proper drainage, ample nutrients, and excellent water-holding capacity. Use it for all of your seed-starting needs! It also works well as soil for outdoor container plants and indoor houseplants. 

Not Using Plant Labels

Colorful clay plant labels for an indoor herb garden.
Use labels to ensure proper identification of plants.

Forgetting plant labels is an easy mistake, though it has dire consequences. I made this mistake once, and I’ll never make it again! You’ll eventually be able to identify your seedlings, although some plants look similar when they’re young and are unidentifiable. This is especially true for native plants and perennial seedlings; they may be more difficult to identify than fruit and veggie sprouts.

Always use plant labels to ensure you know which plants are which. It’ll allow you to transplant them in spring with proper spacing so that they grow big, tall, and wide. If you forget labels, you may not know what you’re transplanting! This leads to a crowded garden as the plants grow up. 

Most labels you find at the store are plastic, and they add unnecessary waste to your garden. Consider using wood labels to keep inorganic materials out of your backyard. Plastic labels may seem like they last forever, though they eventually break into a million pieces after a growing season or two. 

Bringing Pots Indoors

Three rows of plastic milk jugs filled with soil and seeds, taped in the centers with colored tape and labeled with seed names, placed on the steps.
Milk jugs and humidity domes offer enough protection from the snow while insulating seedlings.

While your garden plants grow big and tall, they must undergo extreme winter weather! Winter is a time of stormy, snowy, and wet days with little respite from the cold. You may feel the urge to bring your young winter sown seedlings indoors to weather a harsh frost—resist this temptation, as it can be a big mistake to warm them up!

Cold-loving seedlings are hardy, and they prefer growing under the cool, moist conditions of the outdoors. Milk jugs and humidity domes offer protection from snow while they insulate the young plants. Ensure the plants have cover, and leave them be for all of winter. 

If you brought your seedlings inside for a few hours, promptly bring them back outside. If they’ve lived longer than a day indoors, leave them be and remove the containers’ tops. Cultivate the plants indoors and transplant them outdoors after the danger of frost passes.

Too Much Sun

A shot of rows of milk jugs exposed in sunlight in an area outdoors
Too much sunlight will cause scorching, dead plants, and dry soil.

Though seeds need direct sunlight to grow well, they don’t like too much. Excessive sunlight causes scorching, dead plants, and dry soil. Cold-loving species generally need less light than warm-loving ones, and they thrive with the filtered light common in winter.

The best place for milk jugs, potted plants, and containers is a site with partial sun, having between three and six hours of sunlight. Alternatively, you can give them dappled sunlight for most of the day. 

Monitor your crops as they sprout, and ensure their soil stays moist and not soggy throughout the season. Remove the tops and domes after the weather warms in spring, and keep the plants happy until they’re ready for transplanting.

Share This Post
Close-up of small plant seedlings with oval, jagged, bright green leaves sprouting from seeds in soil blocks.

Seeds

15 Best Seeds to Start in Soil Blocks This Year

Soil blocking is a productive seed-starting method that suits most ornamental and edible annuals and perennials. As the soil becomes both the growing media and the “pot,” healthy roots move easily to the garden at transplanting. Gardening expert Katherine Rowe explores dynamic varieties for seed blocking this year.

Close-up of winter sowing supplies, featuring a row of white plastic milk jugs repurposed as seed containers, arranged against the wall of a house in a snowy winter garden with patches of green grass.

Seeds

5 Essential Winter Sowing Supplies and Equipment

Now is the time for winter sowing - an easy, resourceful, rewarding way to start seeds working with nature. Using simple containers for homemade “greenhouses,” strong seedlings emerge, ready for transplanting. With a few essentials and repurposed household supplies, we’ll be on our way to (nearly) effortless seed-starting. Join gardening expert Katherine Rowe in all that’s needed for this streamlined approach to seeding.

Close-up of a starting tray with sprouted seeds showing thin upright stems and slightly curled green oval leaves on a windowsill, ideal for starting seeds in Zone 2.

Seeds

When to Start Seeds in Zone 2

If you want to garden in some of the coldest regions in the U.S., you’ll have to do some serious planning. Gardening in zone 2 is one of the biggest challenges a gardener can have. In this article, plant expert Matt Dursum shows you when to start seeds in zone 2.

Close-up of tiny sprouted seeds that are never sown indoors, displaying thin vertical stems and pairs of rounded green cotyledons emerging from loose brown soil in a garden.

Seeds

13 Seeds You Should Never Start Indoors

Starting seeds indoors is viable and productive. It gives seedlings a jumpstart on the growing season as we move them outdoors in warmer temperatures. But not all seeds are best for indoor sowing. As we plan our spring gardens, explore which seeds not to start inside this winter with gardening expert Katherine Rowe.

Young lupine sprouts, showcasing native plant seed germination, feature slender stems, rounded cotyledons, and emerging soft, palmate leaves growing from the soil.

Seeds

7 Tips to Improve Native Plant Seed Germination

Native plants are often easier to sow than non-native ornamental species—they adapt well to local climates and sprout with little assistance. If you’re sowing them and notice sparse sprouting, use these seven tips from native plant gardener Jerad Bryant to boost their germination rates.