Red cedar is best propagated by seed collection and planting. Some types also can be propagated by cuttings, but seeding is a reliable method for all kinds of red cedar. This tree is most commonly found in the northern and eastern United States and into Canada, and is also called Eastern red cedar, or Juniperus virginiana. Another tree also referred to as red cedar is the giant Pacific Northwest tree named Thuja plicata, which can be propagated in much the same way.
Collect red cedar cones when they are ripe, and have changed color from yellow to brown. Gather as many seeds as you can find. Because germination rates for red cedar aren't very good, you'll want to have as many chances as possible.
Lay the seeds out in a warm, flat area indoors on paper towels where they will be undisturbed. They should be completely dry before you store them for later planting. Setting up a box fan that doesn't rotate nearby or in the same room will help them dry more quickly.
Shake the seeds out of the cones after they are dried, which should be in a couple of days. Don't separate the seeds from their casings, as these protect them until germination. A careful fanning can help separate the seeds from the chaff clinging to them as well.
Clean the seeds by rubbing off surface dirt and debris; don't use water, as this can cause the seeds to rot. Cleaning is especially important if you are not replanting the seeds quickly.
Put the seeds in sealable containers and store them in a dry, dark place with a temperature range of 20 to 40 degrees Fahrenheit.
Stratify the seeds a month or more before planting. Moisten thin layers of peat moss and sandwich layers of seeds in between them. This will help the seeds develop over the storage period. Place the peat moss and seeds in sealable containers and store for between 30 and 120 days at about 40 degrees Fahrenheit.
Plant seeds in the spring. Red cedar is an evergreen, but will germinate best in the spring when temperatures warm up. Sow at a depth of a quarter-inch or half-centimeter in moist soil.