VALUE AND USE
SPECIES: Pteridium aquilinum | Bracken Fern 



WOOD PRODUCTS VALUE : 
NO-ENTRY


IMPORTANCE TO LIVESTOCK AND WILDLIFE : 
In Montana, elk eat bracken fern only in June when new fronds are
unfurling [247].  Likewise New Jersey deer use is restricted to spring
fiddleheads [227].  In the southern states bracken fern is ranked as a
low-use forage for deer which eat it only in the spring [92].
White-tailed deer eat bracken fern in trace amounts only in the summer
and fall [132] or not at all [116].  However, bracken fern foliage
accumulated high concentrations of nutrients and was heavily used by
deer in Pennsylvania during the first spring following fire [99].
Rabbits occasionally eat the fronds and rhizomes [181].

Goats are the only livestock that normally eat bracken fern [79].
Cattle feeding on lush grass may eat bracken fern for roughage or if it
is mixed in hay [33,62]. In the Pacific Northwest sheep avoid mature
fronds of bracken fern so it increases in cutover areas grazed by sheep
[128].  The fronds may release hydrogen cyanide (HCN) when they are
damaged (cyanogenesis), particularly the younger fronds [42,96].
Herbivores, including sheep, selectively graze young fronds that are
acyanogenic (without HCN) [43,96].

Despite bracken fern's production of bitter-tasting compounds, chemicals
that interfere with insect growth, and toxic chemicals, bracken fern
hosts a relatively large number and variety of herbivorous insects
[141,142].  In Great Britain 27 to 35 insect species eat bracken fern.
The number and diversity of insect species increase toward the end of
the season, possibly because of declining levels of toxic chemicals
[141].  A study in the southwestern United States found only five to
seven insect species feeding primarily on bracken; however, in the
Southwest bracken fern grows in a very restricted area [142].  Some
North American sawflies feed on bracken fern [141].


PALATABILITY : 
Bracken fern's palatability is usually nil to poor, although
occasionally it is eaten by livestock after autumn frosts [234].  In the
southern and northeastern United States, newly emerging fronds of
bracken fern are most palatable to deer and livestock [92,227].  Cattle
sometimes eat it for roughage [62].  A study using captive mule deer
gave bracken fern a low preference rating, since the deer only consumed
it in July [210].


NUTRITIONAL VALUE : 
The crude protein content of bracken fern decreases during the growing
season, from 20 to 25 percent to 5 to 10 percent in fronds and from 10
to 15 percent to 2 or 3 percent in petioles (stems) [141].  Frond
carbohydrate levels are highest early in the summer and begin to drop by
mid-July [243].  Lignin, tannin, and silicate levels tend to increase
through the growing season making the plants less palatable [141].
Cyanide (HCN) levels fall during the season as do the levels of a
thiaminase which prevents utilization of B vitamins [141].  Tannin
production may be related to edaphic conditions; water stress may reduce
the amount produced [226].

Toxicity:  Bracken fern is known to be poisonous to livestock throughout
the United States, Canada, and Europe [92,234].  Losses are greatest
when livestock is fed hay mixed with bracken fern [234].
Simple-stomached animals like horses, pigs, and rats develop a thiamine
deficiency within a month.  Vitamin B1 is effective in curing the animal
if it is administered early [67].  Acute bracken poisoning affects the
bone-marrow of both cattle and sheep and causes anemia and hemorrhaging
which is often fatal [67,104].  Bright blindness and tumors of the jaws,
rumen, intestine, and liver are also found in sheep feeding on bracken
fern [104].  Sheep and cattle are most often poisoned by bracken fern
when young animals are moved from an area without bracken fern to a
field containing the fern.  Cumulative poisoning may occur in older
sheep that have ingested small amounts of bracken fern over a period of
years [104].


COVER VALUE : 
Bracken fern clumps are used for cover by deer in England [43].  Birds,
including pheasants, meadow pipits, and grouse, may use it for escape
cover.  In England, woodcocks, chats, and wrens nest in bracken fern
[172,181], and small animals such as foxes, rabbits, voles, shrews, and
mice find cover in it [181].  Sheep ticks and other insects are often
found in the decomposing litter of bracken fern [23,77,104].


VALUE FOR REHABILITATION OF DISTURBED SITES : 
Nonnative grasses are often seeded onto disturbed sites in some areas of
the West to control erosion.  Sites with predisturbance cover of bracken
fern do not normally need seeding and should be low in priority for such
activities [229].


OTHER USES AND VALUES : 
Bracken fern was considered so valuable during the Middle Ages that it
was used to pay rents [202].  Bracken fern was used as thatch for
roofing and as a fuel when a quick hot fire was desired.  The ash was
used as a source of the potash used in the soap and glass industry until
1860 and for making soap and bleach.  The rhizomes were used to dye wool
yellow and in tanning leathers [202].  Bracken fern is still used for
winter livestock bedding in parts of Wales since it is more absorbent,
warmer, and easier to handle than straw [77,125].  It is also used as a
green mulch and compost [70,183,202].

Bracken fern is most commonly used today as a food for humans.  The
newly emerging croziers or fiddleheads are picked in spring and may be
consumed fresh or preserved by salting, pickling, or sun drying
[120,202].  Both fronds and rhizomes have been used in brewing beer, and
rhizome starch has been used as a substitute for arrowroot [232].  Bread
can be made out of dried and powered rhizomes alone or with other flour
[202].  American Indians cooked the rhizomes, then peeled and ate them
or pounded the starchy fiber into flour [102,107,149,183].  In Japan
starch from the rhizomes is used to make confections [120,202].  Bracken
fern is grown commercially for use as a food and herbal remedy in
Canada, the United States, Siberia, China, Japan, and Brazil [70] and is
often listed as an edible wild plant [107,120].  Powdered rhizome has
been considered particularly effective against parasitic worms [79,202].
American Indians ate raw rhizomes as a remedy for bronchitis [79,183].

Bracken fern has been found to be mutagenic and carcinogenic in rats and
mice, usually causing stomach or intestinal cancer [62,63,70,80].  It is
implicated in some leukemias, bladder cancer, and cancer of the
esophagus and stomach in humans [63,80].  All parts of the plant,
including the spores, are carcinogenic, and face masks are recommended
for people working in dense bracken [63].  The toxins in bracken fern
pass into cow's milk [62,70,80].  The growing tips of the fronds are
more carcinogenic than the stalks [62,141].  If young fronds are boiled
under alkaline conditions, they will be safer to eat and less bitter
[63,70,120].

Bracken fern is a potential source of insecticides and it has potential
as a biofuel [140].  Bracken fern increases soil fertility by bringing
larger amounts of phosphate, nitrogen, and potassium into circulation
through litter leaching and stem flow; its rhizomes also mobilize
mineral phosphate [28,140,157,158,242].  Bracken fern fronds are
particularly sensitive to acid rain which also reduces gamete
fertilization.  Both effects signal the amount of pollutants in rain
water making bracken fern a useful indicator [64,65,66].


MANAGEMENT CONSIDERATIONS : 
Competition:  Bracken fern is competitive plant that invades cultivated
fields and disturbed areas [54,79,129,218,222,234].  It effectively
competes for soil moisture and nutrients.  Its rhizomes grow under the
roots of herbs and tree or shrub seedlings, and when the fronds emerge,
they shade the smaller plants.  In the winter dead fronds may bury other
plants and press them to the ground [46,117,150,162].  On some sites
shading may protect tree seedlings and increase survival [162].  In a
western Washington study, dense bracken fern protected planted
Douglas-fir seedlings from snowshoe hare and black-tailed deer browsing
until the trees overtopped the bracken fern; tree growth, however, was
slower than normal [54,55].  Control may be needed until tree seedlings
are taller than the bracken fern and sturdy enough to withstand the
weight of dead fronds [112].  Scots pine (Pinus sylvestris) has
sucessfully invaded stands of dense bracken fern (var. aquilinum) [159].

Allelopathy:  Bracken fern's production and release of allelopathic
chemicals is an important factor in its ability to dominate other
vegetation [13,84,86].  The release of these toxic chemicals varies by
environment or perhaps by variety of bracken fern.  In tropical areas
rainfall leaches toxins from green fronds.  Farther north no
allelopathic chemicals are released from the green fronds but are
readily leached from standing dead fronds [84].  In the Pacific
Northwest, water extracts from green fronds did not inhibit sampled
plants, but extracts from litter did [52].

A Pacific Northwest study found that water-soluble extracts from dead
bracken fern fronds affected thimbleberry (Rubus parviflorus) and
salmonberry (R. spectabilis) germination but did not affect Douglas-fir
(Pseudotsuga menziesii).  Bracken fern litter reduced the emergence of
all three species [217].  In Pennsylvania, water extracts from green
fronds reduced germination of black cherry (Prunus serotina) [124].  In
an Idaho study, when subalpine fir (Abies lasiocarpa), Engelmann spruce
(Picea engelmannii), Douglas-fir, and grand fir (Abies grandis) seed was
sown under bracken fern, most of the new germinants died before shedding
seed coats [71].  Herbs may be inhibited for a full growing season after
bracken fern is removed, apparently because active phytotoxins remain in
the soil [124,87].

Bracken fern control:  Timing is important in any treatment of bracken
fern [68, 154,155,244].  The most effective time for treatment is summer
just after the new fronds have fully expanded and starch reserves in the
rhizome are at their lowest level [31,136,154,155,160,196,218,243].  Two
or more annual treatments and combinations of cutting and herbicide are
more effective than single treatments or even single annual treatments
[154].

Mechanical Treatment:  Cutting early in the summer, allowing the
rhizomes to regenerate a second crop of fronds, then recutting will
deplete the resources of the rhizome much faster than a single cutting.
However, single, annual cuttings or deep ploughing can be effective
during midsummer [70,154].  A north Florida slash pine (Pinus elliotii)
site with small amounts of bracken fern was clearcut in late fall.
Debris and residual vegetation were mechanically chopped the following
April and again in August, followed by mechanical preparation and
planting.  Bracken fern amounts remained fairly steady and did not
increase to harmful levels [35].

Biological control:  Biological methods for control of bracken fern in
Great Britian are being investigated and two South African moths
(Conservula conisigna and Panotima sp. near angularis) appear promising.
Both moths are capable of severely damaging the fronds in the spring,
but no biocontrol agent capable of damaging the rhizomes has yet been
identified [146].  Lawton [143] evaluates potential control insects and
potential problems with their use.  The possibility of using disease
fungi, either alone or in conjunction with herbicides, to control
bracken is also being studied [25].

Chemical control:  Asulam is a relatively specific and environmentally
safe herbicide that is very effective for bracken fern control
[26,118,129,160,197].  Asulam is more effective if the bracken fern is
cut first [54].  Dead fronds may need to be cut away from growing trees
after spraying with asulam [212].  Glyphosate (Roundup) is also
effective and reduces carbohydrate reserves of the rhizome
[12,26,48,136,160,241].  Other effective chemical controls include
amitrole-T, dicamba, karbutilate, picloram, 4-CPA, sodium
chlorate/borate, chlorthiamid, and dichlobenil [31,165].  The
effectiveness of these is variable in the Pacific Northwest [26].  Two
applications increases control [222].  Methods and timing of herbicide
application are discussed by Hamel [103], Robinson [201], Miller and
Kidd [166], and Burrill and others [26].  Spraying vegetation with other
herbicides may reduce competition and allow bracken fern expansion
[182,219].

Related categories for Species: Pteridium aquilinum | Bracken Fern