Cranberry plants (Vaccinium macrocarpon) are low-growing, berry-producing vine-like shrubs that are native to regions in eastern North America. They are usually grown in sandy, acid-rich soil with bog-like growing conditions. Growing cranberries from seed requires perseverance and commitment, since the seeds can require a long period of time before germinating.
Fill 3- or 4-inch wide pots with enough lime-free sterilized growing medium to fill the pots to within about 1/4 of an inch from the top of the rim.
Firm down the soil in each of the planting pots using your fingers, a piece of wood or a metal spoon. Transfer all the pots into an irrigation or watering tray. The tray should be able to hold about 2 inches of water.
Pour enough water into the tray so the growing medium in the pots will soak up the water and become well-moistened. Pack the soil down one final time. Pour out the remainder of the water, if there is any.
Poke two to three 1/4-inch-deep holes in each pot. Drop two cranberry seeds into each of the holes. Sprinkle over the top of each pair of seeds approximately 1/4 inch of the growing media.
Place the tray of pots in a location in your home that will stay consistently around 65 to 70 degrees F for four weeks. Provide as much bright light as possible but, if possible, not direct sunlight. Keep the growing medium moist in each of the pots; add water to the tray as needed.
Transfer the tray of pots into a location where the temperature will be between 25 and 40 degrees F for six weeks. Maintain the moisture levels by adding water to the tray when required. The temperature change is beneficial to hasten germination.
Put the tray of pots into an area where the temperature will stay fairly consistent between 40 and 55 degrees F. Leave the tray of pots in this location for germinating the cranberry seeds. Germination of cranberry seeds can begin in as little as three weeks, or can take several months. Transplant the cranberry seedlings into their permanent location outside after they've become well-established.