Cultivation of Cheilanthes species
(with focus on Cheilanthes feei and Cheilanthes lanosa)
Hope Diamond and Lucinda Swatzell, 2003
Southeast Missouri State University, Cape Girardeau, MO 63701
|Cheilanthes, the Lip Ferns or Rock Ferns, is a genus
of xerophytic ferns that inhabit rock faces or rocky slopes. Cheilanthes species are irresistibly beautiful, and
the temptation to remove them from their habitat to establish them elsewhere
rhizotomously is great. However, results are often disappointing and
removal is often illegal.
Cheilanthes lanosa; Photo by Maria Palmieri, 2000
|Much to the fern lover's disappointment, these
ferns are slow to re-establish when disturbed and somewhat difficult to
cultivate. There are several reasons for this. First, the adult
grows slowly and does not compete well with other species (unpublished
Cheilanthes feei; photo by Maria Palmieri, 2000.
|Protect wild ferns! Always consider the impact of removal. Although some ferns grow like weeds, others do not. Also, ask your local wildlife specialists if the ferns you want are in protected areas. Cheilanthes are illegal to collect without a permit in state and national parks and forests. Always, remember too, to respect the rights of land owners. Ask for permission before you collect.|
Cheilanthes lanosa; photo by Hope Diamond, 2002
|Second, the early stage of the ferns' life cycle, the
protonemata, which is the filament of cells that form following germination
and which eventually develops into the gametophyte, limits the conditions
under which the ferns can live (Nondorf et al, 2003).
Left: Cells arrested in the protonemal state during callus induction. Note the end on end filamentous arrangement. Wild protonemal cells quickly divide in 2 dimensions into a heart-shaped prothallus.
Cheilanthes is best cultured from spore, and spores can be collected without permanent damage to the plant. Spores should be harvested in November and December. Harvest spores by clipping sporophylls (fronds that bear spores). Support the rhizoid ball carefully during the harvest to avoid dislodging the fern. Harvest sporophylls in a haphazard manner to reduce impact on the population. Avoid removal of all the fronds on one plant and randomly choose individuals. Bag the fronds in zippable plastic food bags. (Yes, glass containers would be better; ferns spores adhere to plastic because of the static. ...... But we would prefer that you do not hike with glass in your backpack!)
Once you are back in your greenhouse, kitchen, or other favorite haven, place the sporophylls loosely in glass canning jars or Petri dishes. Store the fronds at 4°C (refrigerator), in the dark, and slightly ventilated so that they dry. After a few months, you can harvest the spores.
Remove the dried fronds from storage. Crush them thoroughly with a mortar and pestle (a good investment for any fern enthusiast). Once the fronds are completely crushed, filter the stems pieces and hairs out with a tea strainer and an animal hair artist brush.
|Fern spores vary in size. For example, C. feei spore is 67 μm in diameter and C. lanosa spore is 41 μm in diameter (Knobloch, 1969). A microsieve would eliminate most leaf, rhizome, or root particles and leave clean spore. However, the organic matter and dirt carries fungal components that may be beneficial (Palmieri and Swatzell, 2003). In addition, C. lanosa is often resistant to harvest and viable spore can remain in the sporangia, which would be removed with a microsieve.|
|Sow the Spores
In shallow glass containers, such as saucers, plates or Petri dish bottoms, pack clean fine sand. Saturate spore material with liquid growth medium or fertilizer: 1 part spore material and 2 parts liquid. McEnroe and Reid (1981) used Hoagland's No. 2 solution for Cheilanthes microphylla. The fertilizer is important only to a certain extent. It should contain high calcium, even for those species that do not inhabit calcareous soils. It should be low in nitrogen. A half-strength mixture of commercial houseplant medium will suffice. In this case, add a pinch or two of bone meal beneath your sand (Seigler, http://www.amerfernsoc.org/growdry.html ). Ours: half-strength tissue culture medium or spore germination medium (Smith, 1992). Gently squirt the spore material in a spiral pattern over the sand with a baster, blue bulb, or Pasteur pipette. Next, moisten the sand from beneath by squirting growth medium in a thin forceful stream around the outer edge of the sand.
Cover cultures with aluminum foil and incubate at 25-30°C for 1-1.5 wk (don't worry about air flow the first week). Next, remove the foil and place cultures in bright indirect light. Place cultures under glass, but allow baffled air flow. Glass Petri dishes are perfect, but an old fashioned dome, propped up 0.5 cm, is also good. Spores stored for more than a few months will need to be coaxed out of dormancy. Fresh spores (2-3 mo storage) germinate in 10 d in the dark. Spores that have been stored longer will need 1-1.5 wk of darkness, followed by 1-1.5 wk of heavy shade, and 1-1.5 wk of continuous indirect white light.
|The correct watering regime is crucial. After planting, the cultures will remain moist under aluminum foil. When they are uncovered, and air is allowed to flow, the cultures should dry very slowly. The ideal condition is one in which moisture beads on the glass, and the sand feels dry to the gentle touch, but not so dry that it forms a hard cake. The sand should remain loose. Water with ddH2O only, with a squirt bottle to force water under the sand, and only around the edges of the sand. NEVER water gametophytes directly. They will die or "burn." Adopt this mantra: Water vapor is good; standing water is bad.|
|If you should goof and the gametophytes
should dry, simply water as before. They will rehydrate and produce
new filaments from their margins.
Left: A "dead" gametophyte (clear, brown cells) gives rise to a new filament (green). These are protonemal in nature and will give rise to a new gametophyte.
Gametophytes are typically apogamous (a "vegetative" form of sex). Dependent on the species, in 4-6 wk sporophytes will emerge from the gametophytes. Some species can remain under glass. For example, C. lanosa loves humidity and fronds do not exceed 12 in. Still, the sporophytes can be transplanted outside. Once again, humidity is important, but the soil must be well drained and watered from beneath. Avoid chlorinated water. Note: Some species are evergreen and some species sacrifice fronds each season. A "failing" plant may not be failing, but can be revived. Gently uproot the plant, clip the fronds, and place in a zippable plastic food bag. Store in the refrigerator 3-6 mo and revive in the spring. Fiddleheads will pop up again!
|Above: Sporophytes emerge from C. feei
gametophytes. On C. feei, the sporophyte pad (light green
structure at right arrow) is light green. It may be brown on your
favorite species. The emergent sporophyte is preceded and surrounded by a mass
of white hairs (trichomes; left arrow).
Right: Young C. feei sporophytes rise above the gametophyte bed.
Yes, we know. To us, their habitat is arid. .... But look closely at your cultures or the rock crevices in which they grow. Their substrate is actually wet (Hayes, 1924). Rock crevices, particularly sedimentary rock, silt catchments, or humus mats on stone outcrops retain moisture. ..... And remember, these ferns are adept at extracting moisture out of "thin air" (Pickett, 1931; Quirk and Chambers, 1981). Hence, the secret to growing Cheilanthes is to provide moisture that the fern can access without immersion.
Right: Sand grains glisten with moisture under a mat of C. feei gametophytes. To touch or the naked eye, these appear dry.
Hayes, DW. 1924. Transactions of American Microscopical
Knobloch, IW. 1969. The spore pattern in some species of Cheilanthes. American Journal of Botany 56(6):646-653.
McEnroe, EP, MS Reid. 1981. Propagation and culture of lip fern, Cheilanthes myriophylla Desv. Flower and nursery report for commercial growers. California University, Berkeley, Cooperative Extension Service. p. 2.
Nondorf SL, MA Dooley, M Palmieri, LJ Swatzell. 2003. The Effects of pH, temperature, light Intensity, Light quality, and moisture levels on spore germination in Cheilanthes lanosa of southeast Missouri. American Fern Journal: in press.
Palmieri M, LJ Swatzell. 2003. Presence and distribution of
mycorrhizal fungi in association with Cheilanthes lanosa in southeast
Missouri and southern Illinois. International Journal of Plant Sciences.
Pickett FL. 1931. Notes on xerophytic ferns. American Fern Journal 21(2):49-57.
Quirk H, TC Chambers. 1981. Drought tolerance in Cheilanthes with special reference to the gametophyte. Fern Gazette 12(3):121-129.
Seigler, D. http://www.amerfernsoc.org. Growing Xerophytic (Arid-Loving) Ferns.
Smith, RE. 1992. Plant Tissue Culture. Academic Press, Inc., San Diego, CA.