How can a used milk jug help birds and butterflies?
by Ellie Nowels
Most songbirds need soft bodied insects such as caterpillars to feed their young. A bird as small as a chickadee can use 6000 or more caterpillars to feed one brood! Most species of caterpillars require specific native plants to feed on. So how does a nature advocate successfully nurture enough native plants to fill these requirements?
Many gardeners are turning to an inexpensive way to propagate native plants without greenhouses or complicated indoor setups. Getting native plants to germinate is more complicated than starting traditional garden plants, since many native plant seeds require a period of cold and moist dormancy, called stratification. The length of time varies based on the species, ranging from 10 to 120 days or more. Milk jug germination (called “winter sowing”) is an easy and inexpensive way to start seeds outdoors, with the jugs acting as miniature greenhouses.
Why winter sow?
- It’s much easier than trying to start native plants indoors.
- Takes the guess work out of tracking days for cold moist stratification.
- More species of native plants are available as seed than you will find at the nursery.
- You will know exactly what plant is in your container when it germinates. (It can be difficult to identify plants at the seedling stage, making it easy to mistake your seedlings for weeds).
- It’s inexpensive and produces strong, healthy plants.
- Hardening off process is simpler (no carrying plants outside and back inside every day!)
- Less potential for “damping off”.
When to Winter Sow
From the winter solstice (December 21) through February. Night temperatures in your area should be consistently lower than 50 degrees.
What seeds can be winter sown?
There are too many species that can be winter sown to list here! I confine my species to native perennials, mainly those needing stratification. Pick your favorites species and experiment! You can either purchase seeds or harvest them from your garden. Many organizations have seed swap events where you can obtain seeds and planting advice. The Seed Vault in Westerville also stocks seed for several native species.
Most native plants have just a simple need for a set number of days of cold moisture, so they are good candidates for winter sowing. A few species can just be sown in the spring when the ground warms up (Germination code A*) but they will also do well when winter sown.
Choosing a container
Milk jugs are not the only container that you can use. People use a variety of containers, from big salad containers to large storage boxes filled with soil or with individual pots; some even use resealable plastic bags hung from support rods. Some of us have found that clear, rather than translucent containers allow the seeds and seedlings to dry out too fast or get too hot. No matter what container you use, allow 3-4 inches of soil and enough room above the soil for the seedlings’ growth. Top coverings need enough holes punched for all the soil surfaces to stay moist.
How to winter sow
You will need a good potting mix, containers, and seeds. Also have something to label your containers, a sharp tool, and tape.
- Containers will need drainage holes on the bottom. I use a 3/8” drill bit and space out 5-6 drain holes; others use a hot glue gun or knives to make the holes.
- Using a knife or sturdy scissors, cut the jug almost in half, going about ¾ of the way around, leaving the handle intact as a hinge.
- Remove the cap. The opening at the top should be sufficient to let in enough rain and snow to keep the soil moist.
- Pack the bottom of the jug with 3-4 inches of dampened potting mix.
- Scatter the seeds (one species per jug) on the soil. Many species will have germination codes* that say to “surface sow”; press those down into the damp soil but don’t cover them. Other seeds can be covered with a light sprinkling of soil.
- Label the outside of the jug with the name of your plant, using a fade resistant Sharpie, and create a marker of some kind for the inside, too. Otherwise if your outside label fades, you may not know what’s growing! Write the name of the plant on the bottom of the jug too; this seems to be the most resistant to fading.
- Close the jug and secure the top to the bottom. Many people use duct tape. Some others experiment with punching holes top and bottom and using twisty ties or pipe cleaners to hold the top and bottom together. The top and bottom need to fit together securely enough to form a tight seal.
- Place your containers where they can have some sun, rain, and snow (not under an overhang). If your area is prone to high winds, tie the jugs together by their handles, or run a stake through the handles.
The edges of the raised bed keeps jugs from falling over.
Monitoring your containers
- Periodically check for moisture levels, especially if it’s been a dry winter. Don’t water frozen soil, but on days above freezing, look for condensation in the container; if you see condensation it doesn’t need watering. If you do need to water, water gently (tilt the jug and water down the side of the jug, or use a spray bottle; just avoid pouring in water in ways that will disturb the seeds). You can also water from the bottom.
- If there have been high winds, check to see if any have fallen over.
- During unseasonably warm spells, you might need to open the jugs to keep seeds or seedlings from getting too hot. You can also move them into a spot that doesn’t get full sun.
When to open the containers and when to transplant the seedlings
When the seeds begin to sprout, then it’s time to open the containers. They will probably need some watering at this point. If there are cold snaps, shut the jugs up again or cover the jugs with sheets or other protection.
In spite of their protective containers, the seedlings will still need to be hardened off before transplanting. Take off the lid off the container for a couple of hours, every day for a few days, then do it all day for a few days up to a week or two before transplanting them. This will allow them to adapt to the strength of the unfiltered sun and breezes.
When the seedlings have 2 sets of “real” leaves or are 1” to 2” tall, it’s okay to transplant them into pots for more growth, or even into the garden. If you have many tightly packed seedlings, transplant them in bunches (“hunk of seedlings”method).
This foxglove beardtongue is ready for transplanting using the “hunk of seedlings” method. Trying to transplant hundreds of individual seedlings would be impossible! But dividing out chunks of several seedlings keeps roots intact and will make for a nice group of plants. Water your container and let it drain. You want to remove the top of the container (if you are still using it) and then push on the bottom of the container to remove the entire soil ball. Lay it on the ground. Cut the soil and seedlings into smaller chunks (I cut them to fit my 2-inch pots). Water them with 1/4 strength of fertilizer of your choice. You can also separate the larger seedlings with a fork or spoon for repotting. No matter what, separate them out before the roots get too long for the pot.
*Stratification and germination codes
Germination codes tell growers how much stratification a species needs, along with any other requirements. Prairie Moon Nursery is a great resource – each plant has a germination code listed, and they provide a detailed explanation of those codes here: https://www.prairiemoon.com/how-to-germinate-native-seeds.html
Most native plants have just a simple need for a set number of days of cold moisture, so they are good candidates for winter sowing. A few species can just be sown in the spring when the ground warms up (Germination code A) but they will also do well when winter sown.
Success! Winter sown plants on their way to a plant sale on Memorial weekend.
Sources:
Most info was taken from Winter Sowers – the Original – Facebook group. (Members do need to be approved to join, but then you will have access to their 7 sets of guides that cover many topics. A great resource!)
Some other sources for those not on Facebook; these cover the basics but are not necessarily focused on native plants and the stratification process).:
https://www.sandiaseed.com/blogs/news/winter-sowing (focused on vegetables, not natives, but covers the basics of the process)
https://getbusygardening.com/winter-sowing-faqs/
https://104homestead.com/winter-sow
https://ocean.njaes.rutgers.edu/wp-content/uploads/2024/01/Winter-Seed-Sowing-Handout-Final.pdf (covers basics, with links you can scan for more info).
Starting native seeds:
https://njaes.rutgers.edu/fs1329/ (not specifically about winter sowing, but covers seed saving from native plants and propagation)
Germination codes: https://www.prairiemoon.com/how-to-germinate-native-seeds.html
Homegrown National Park is a movement advocating for increasing biodiversity at home. Here’s their page on winter sowing.
Many gardening groups will hold workshops on winter sowing during winter. Check out https://wildones.org/ or other environmental/gardening groups for classes.