Many flower seeds need a period of cold temperatures to break their dormancy so they will germinate prior to sprouting — especially plants native to Western Pennsylvania. Butler County Master Gardeners say you don’t need to waste space in the freezer by putting germinating flower seeds in them — just put them outside in the winter in a protective container.

Mary Reefer, a Butler County Master Gardener, said people can use containers such as milk jugs and pop bottles to create little winter greenhouses for certain seeds. The seeds will germinate inside the containers, and then they can be easily moved into a flower pot or garden bed once the weather is warm enough.

“You can basically get these planted and forget about them until you're ready to transplant,” Reefer said. “This way the frost is not a problem. They are in a protective environment, you know exactly what’s in there.”

Reefer said Master Gardeners use this method of winter seeding, and they recommend people do the same to be cost-effective and efficient.

“Doing this will take care of stratification without having to put seeds in your freezer or fridge for months,” Reefer said. “Find some milk cartons or plastic milk cartons, 2-liter bottles, even containers you buy spinach in or rotisserie chicken can be relatively cheap.”

According to Reefer, 1-gallon milk jugs make the best container planters because they are big enough to hold most sprouts that need to germinate in the winter.

Just make sure the container being used is washed before placing soil and seeds inside it.

“First of all, it’s recommended that you wash the jugs with soapy water so you get anything out,” Reefer said. “You discard any lid, you take a drill or a punch of some sort and put some holes in the bottom of the jug.”

Container planters are basically miniature greenhouses, which keep the seed insulated during cold temperatures at night while creating a warmer internal climate during the day. Reefer said condensation created by the alternating temperatures helps water the seeds inside the container as well.

“It’s best to take some scissors and cut halfway up the milk container about three quarters of the way around so you have a hinge,” Reefer said. “That way you can put your soil and seeds in, put duct tape in and seeds. You’re making a mini-aquarium, so water will condense and it will water the plants.”

Reefer said be aware of which plant seeds benefit from stratification prior to their planting. She said plants native to Western Pennsylvania, like milkweed, black-eyed Susans, poppies, snapdragons, hollyhocks, lobelias and the blazing star can benefit from this preplanting practice, while produce could be harmed by it.

“I would not grow things like peppers, tomatoes, cucumbers,” Reefer said. “They are warm-season plants and will not do well with winter planting.”

Reefer said placing seeds in a repurposed container is similar to planting them in a pot. However, make sure the planter conditions are good for the seed so it can grow properly.

Reefer suggested people put coffee filters in the bottom of the container to keep the soil in. Then, moisten the starting soil enough that it’s not dripping wet, but damp. Put about 3 inches of soil in the bottom of the container, but make sure there is room for plants to grow inside and then be transported.

“It’s a good idea to get a Popsicle stick and mark what seeds are in that container,” Reefer said.

After preparing the soil and the seed, seal the container with duct tape, and take it outside and start it in a south-facing location, so it will get as much sun as possible. As the temperature gets warmer and moisture is sufficient, the seeds should germinate, but Reefer said it might take a while.

“Once it warms up significantly, this is a greenhouse, you don;t want them killing them with the heat,” Reefer said. “That’s when you want to open up the container and introduce real sunlight and letting heat escape.”

Reefer added that a gardener should check on the condensation in an outdoor container to make sure a seed is getting enough moisture.

“You want to see condensation on the top of a jug, which means it’s watering itself. If not, you might want to add some water through the lid hole,” Reefer said.

Once spring hits and the seed has sprouted enough to be placed in the ground, the gardener should carefully transport it from its container home to a garden plot. Reefer said the soil will then be a good temperature to grow the sprouted seed.

“Then you transplant it into your garden when it’s advantageous and the soil is warm enough,” Reefer said. “It’s a very simple way to get seedlings to plant.”

Mary Reefer is a Penn State Extension Butler County Master Gardener.

For more information on Penn State Extension Master Gardener programs, visit the Butler County chapter’s website at extension.psu.edu/programs/master-gardener/counties/butler.