What is winter sowing?
Winter sowing is an easy germination method of sowing seeds outdoors during the winter. Allowing seeds to experience the ups and downs of winter temperatures to encourage them to germinate in Spring. This method is generally done with seeds that require a period of cold stratification.
Winter sowing involves sowing seeds in containers and these containers will act as mini-greenhouses. After sowing, containers are placed outside during winter. They do best in a Southern exposure where the sun is strongest.
Seeds can be started January-April and will be happy with rainstorms or snow coverage. This winter sowing method is effective because it takes advantage of natural environment rather than artificially refrigerating seeds. In fact, users of the method have had success in most hardiness zones. Generally, seeds require oxygen, light, water and certain temperatures to germinate. And the method provides these by using loamy soil which provides a lot of space for the sun’s natural light, oxygen, and the warming of the mini-greenhouse as spring progresses.
Why winter sow?
There are various advantages of sowing seeds outdoors in winter:
- It’s easy
- Selection of plants is amazing
- It’s efficient. You don’t need to use grow lights every single day like you would with seeds indoors.
- You don’t need to worry about having leggy seedlings since seeds are sown outdoors.
- Since mini-greenhouses are placed outside, they don’t take space in the house.
- Prevent your seeds from being eaten or washed away
Choose seeds for winter sowing
There are few restrictions when it comes to seeds for winter sowing. You can choose the seeds of cold-hardy annuals, perennials, herbs or crop vegetables, as long as the plants are hardy and suitable for growing in your climate. Hardy plants can be sown as early as January or February.
Some good choices for your first efforts at winter sowing include:
- brussel sprouts
If you’re unsure whether seeds will work for winter sowing or not. Look for these terms on the seed packets: “direct sow outside in the fall”, “self-sowing”, “direct sow outside in early spring”, “cold hardy”, “cold stratification”.
What you need to sow seeds in winter
- Cordless drill or Xacto knife
- Potting soil
- 3M duty tape or Heavy duty tape
Step By Step
Step 1 – Choose your winter sowing containers. You can use milk jugs, take out containers, soda bottles, ice cream buckets.
By using repurpose recyclable materials, you help to conserve the resources of having to put seedlings into gradually larger containers.
You can choose any items as long as they are made of transparent and be deep enough to hold at least 3 inches of dirt. If there is not enough potting mix, your soil may dry out and the seedlings may become rootbound.
Step 2 – Clean your containers in soapy water. Next, create drainage holes in the bottom of containers. You can use a Xacto knife to do this but I found that using a cordless drill is much easier and faster. All of your containers will require drainage holes along the bottom to allow the water to drain out so the seeds won’t drown.
If you’re using milk jugs or soda bottles, you will need to cut the container in half using a pair of scissors, leaving a hinge for opening the entire top portion.
Step 3 – Create holes in the tops covering to allow rain and moisture to enter the containers. Keep the holes small, to begin with, as temperatures get warmer in spring, you can widen them to allow the plants to gradually harden off. For milk jugs, soda bottles or pop bottles you can skip the holes at the top because you can simply leave the caps off rather than creating holes.
Step 4 – Add potting mix to the containers. Make sure you use potting mix, not garden soil because garden soil could be full of weed seeds. Also, it’s important to buy a good potting mix, don’t go the “dirt cheap” dollar bags of dirt. Cheap dirt may turn into a rock once wet and the seeds will have a hard time germinating.
Step 5 – Wet down the potting mix thoroughly with water, and allow the containers to drain before sowing seeds. If your potting mix is dry, water it a few time to make sure the soil is evenly moist.
You can water the container after sowing seeds. But I prefer to water the potting mix in the container before sowing to avoid the unwanted spacing between the seeds.
Step 6 – Sow seeds on the top of the potting mix. Generally, smaller seeds on the surface and larger seeds should be planted more deeply.
The number of seeds you wish to plant is up to you. But it’s recommended that sowing more seeds than you think you will need because germination rates can be lower than if grown in ideal conditions. But don’t sow too thickly, they will be crowed each other out once they have grown into seedlings.
Step 7 – Label your containers. You may think you will remember, but chances are good you won’t. You can write on duct tape or write directly on the top of the container using a pencil or a Sharpie, but these both will fade eventually.
I recommend using a tape, put it on the bottom of the container so the writing never fade.
Step 8 – Tape the containers closed. You can use 3M duty tape or Heavy duty tape.
Step 9 – Place your winter sown containers outside. Just make sure your containers are in a spot where:
- They are protected from heavy wind
- Will receive moisture and full sun
- Away from animals or kids
Not a lot of care is required for winter sown seed containers once they are outside. However, once the weather begins to warm, you will need to check your containers regularly. You can add more holes to the lid of your containers to harden off plants. Also, make sure water your containers when they become dry.