Spores grow on the bottom of fern fronds. They grow inside structures called sori and are clearly visible as little yellow, green, brown or black clumps on the undersides of the fronds. Once the spores are ready, they are released and blow away in the wind. You can use collect spores from a fern frond and grow young ferns in sealed containers.
Collecting spores. First find a fern you’d like to propagate. Cut or pick a frond and place it spore-side down on a piece of white paper. It’s best to pick fronds with ripe sori, which look scruffy and ready to burst. After the frond sits on the paper for about 24 hours, check the paper. The spores should all fall off and collect on the paper. To separate the spores from their chaffs (the protective casings of the spores) and other debris, lift the paper, tilting it slightly, and tap it from underneath (be careful not to spill the material). Because spores are a bit heavier, the lighter debris and chaffs will be lifted up and can slide off of the paper.
Preparing the container and planting medium. Prepare a clear plastic shoebox with a lid that snaps shut (you can also use clear plastic cups with clear saran wrap and a rubber band to create a cover). The planting medium needs to be sterile, otherwise other fungus can contaminate the container with other fern spores, fungi and mosses. One good planting medium to use is a mixture of two parts perlite to one peat moss.
Pour water into the planting medium until it’s a very muddy consistency. Microwave the planting medium to sterilize it. While the water is still hot but not scalding, tamp it down into the sterile containers (wash them in the dishwasher or bleach them).
Planting and caring for fern spores. Once the planting medium is ready, dust the spores on top of the mix and secure the lid on top of it. To prevent contamination, don’t propagate ferns in the same place on the same day, as the spores can be airborne and land in a nearby container. Label the container with the date and type of fern, and place it by a window or underneath fluorescent lights. Just make sure they are kept at a temperature of 55 to 75 degrees Fahrenheit and are not in direct sunlight.
Don’t open the container for several weeks. Once the fern growth inside reaches about a fourth of an inch tall, mist the container and replace the lid. Mist again in several weeks. Don’t open the lid unless it’s absolutely necessary.
After several months, if the growth is too crowded, thin it so the culture can develop properly and stay healthy. It may take a few months up to a year until the the young clumps can be pulled out of the planting medium with tweezers and planted in their own small containers. The young ferns should be placed in a humid area (in a small greenhouse) until they are about an inch tall. Then gradually start lifting the greenhouse lid so they get used to drier air. Once the ferns get to about 5 or 6 inches tall, they can be moved outdoors.