Ferns of all types can be multiplied using two methods of propagation. Root division, which is the quickest and easiest method resulting in new plants that are ready to plant in their future home almost immediately. Ferns are also readily grown by seed (more correctly the spores) produced in sporangia located on the undersides of fronds. This method is more time-consuming but really no more labor-intensive than starting other types of plant seeds. Gardeners who have experience growing plants that require special stratification treatments or assistance germinating with heat mats and artificial lighting will have no trouble learning how to produce fern seedlings from spores.
Methods To Propagate Ferns
Root division enables a gardener to immediately multiply their stock of ferns and replant in their intended location. Mature ferns (typically more than 2-3 years old) produce the largest divisions, which robustly establish in your landscape. Early in the spring as the new fronds are emerging or late in the summer are the best times to divide and replant ferns. Ensure that the new plants are well watered so that they are established quickly in the garden.
Starting new ferns from spore material will require a bit more investigation. Depending on the type of fern, the Sporangia (spore-containing organs on the undersides of the fronds) will turn brown, black, or even yellow when ready to disperse the spores. The sporangia are always evenly distributed along the frond and will ripen from the bottom to the tip.
Cut a frond, place it on a piece of white paper sporangia side down, and leave for a couple of days to see if the spores are being released. The spores are minuscule and often appear to be brown dust. The spores can be immediately sown or put into a paper envelope to store.
What You Need To Propagate Ferns
For division: A sharp spade or narrow-headed transplanting spade works best to dig up the whole fern, including as much of the root ball as possible. A small folding saw or other sharp knife is useful for dividing the plant up into smaller sections. Larger ferns may be easier to divide using a sharp spade to cut the crown into pieces. Have a filled watering can nearby or a hose to immediately water your new plants in their new homes.
For seeds: A shallow seed starting tray with an accompanying greenhouse dome top are ideal for keeping the spores and potting mix moist until germination begins. Another great way to keep the spores moist is to use disposable cake pans or roasting tins that have a separate plastic cover. 3 or 4-inch plastic pots fit inside of them to make an enclosed atmosphere that is high in humidity and also lets light in. Use a sterilized seed starting mix either commercially blended or homemade.
One homemade recipe to use is two parts perlite to 1 part finely ground and milled sphagnum moss. Heat mats that will maintain a temperature of at least 68F (20C) and a grow light (either fluorescent or LED) placed about 4-8 inches above the pots are the only specialty tools required. At every step of the way ensure that all pots, potting mix, and tools used for transplanting are sterilized to protect the young sporophytes from contamination of any kind.
Best Time To Propagate Ferns
For seeds: Fern spores ripen at different times depending on the type but May through October is a general time frame. Sow the spores as soon as possible after collecting or keep them in a dry and cool location until ready to sow. Many of the native varieties will survive happily for years if kept in a refrigerator or cool spot in a basement.
For division: Dividing can take place either early in the spring or late in the summer depending on how cold your winters are. Northern gardeners will have well-established new plants when grown from division in the spring. Water all plants consistently the first year after planting until new growth emerges.
Steps To Propagate Ferns
Starting ferns by spore propagation may seem intimidating but is very easily accomplished by following these steps. The key to good growth of new ferns is to keep all tools and containers as sterile as possible through every step of the process.
Step 1 - Tap the ripened spores onto a sheet of paper and either sow them immediately or save them in a paper envelope stored in a cool dark spot for use later.
Step 2 - Fill a shallow seed starting tray (that has bottom drainage) or a 3-inch plastic pot with sterilized seed starting mix. Firmly press it down to give the spores a firm surface to lay on. Make sure the potting mix is pre-moistened so that it feels like a lightly wrung-out sponge.
Step 3 - Sparingly sow the spores over the surface of the potting mix. Do not cover anything.
Step 4 - Place the greenhouse dome over the top of the seed starting flat. Alternatively, place the pot inside a homemade greenhouse incubator to retain humidity and moisture in the potting mix.
Step 5 - Place the covered pot on top of a heat mat and under grow lights set to between 8-12 hours of daylight.
Step 6 - Check on moisture levels every day and water the pot from the bottom if necessary. Usually, the condensation produced by the makeshift greenhouse is enough to provide moisture for up to a week. After 7-14 days a green film will form on the potting mix. These are gametophytes forming and are precursors to the prothalli that fertilize and later produce sporophytes which are the actual fern plantlets. This stage will last anywhere from 1-5 months and will require consistent moisture.
Step 7 - Water from the bottom or mist the top surface with distilled water until the sporophytes form and begin to grow. Keep everything under the greenhouse domes. This stage takes anywhere from 6-12 months.
Step 8 - Gradually start to harden off sporophytes once they begin to produce visible fronds. Prop the top of the greenhouse dome a little every few days until they are growing well without the extra humidity.
Caring For Young Ferns as Seedling Plants
Once the plants have been growing without a greenhouse cover they can begin to be thinned or transplanted into small pots as clumps of ferns. Plant 3-4 fern sporelings together in a pot. Divide into individual plants when they outgrow a 4-inch pot or are 10% of their mature size. Harden off indoor-grown plants in the spring to be ready for transplanting one or two weeks later.
Sources: “Propagating Ferns”, University of California Master Gardener. www.ucanr.edu
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Author Robbin Small - Published 12-27-2024 |