Osmunda ferns are large, feathery plants that thrive in moist soil. This hardy variety of fern starts out as a delicate spore. Osmunda ferns are very difficult to grow from clippings. They develop much more easily and quickly (with less threat of disease) when grown from spores. For best results, osmunda ferns must be started in a warm, moist environment, such as a greenhouse. If one isn't available to you, it may be better to purchase a mature adult fern and transplant it directly into the ground.
Plant osmunda fern spores within 3 days of obtaining them, as they tend to lose viability fairly quickly. Fill a small pot with compost-rich soil and scatter the spores on the surface of the dirt. Water the soil until it is moist.
Place a plastic baggie over the pot to seal in the moisture and store it in a greenhouse. Wait for the plantlets (small sprouts) to develop, a process that usually takes very little time.
Transplant the plantlets as soon as they are large enough to remain intact when they're gently tugged from the pot. Pot the plantlets in small clumps of two or three in a large pot.
Leave the potted plantlets in the greenhouse until they appear strong and well-established. They will be small, but healthy looking and bushy, when they are ready to leave the greenhouse. In the meantime, keep the soil moist through daily watering.
Allow the plantlets to develop in the pot for at least 2 years. They will not be stable enough to move outdoors before then.
Select an area that has consistently moist, acidic soil and partial shade. Make sure that the osmunda fern has plenty of room to spread up and out. Dig a hole that is large enough to accommodate the entire root structure of the plant (it should be slightly deeper and wider than the plant's pot).
Slide the osmunda fern out of its pot and place the plant, root-side down, in the hole. Fill in the top and sides of the hole with dirt.
Water the fern during times of drought or extreme heat. As long as you have selected a consistently moist location for the plant, it should be fine the rest of the time. A layer of mulch around the base of the osmunda fern may be required to keep the soil wet.