Pteridium aquilinum (Bracken)
|Also known as:||Western Bracken Fern|
|Family:||Dennstaedtiaceae (Bracken Fern)|
|Habitat:||part shade, sun; poor or sandy soil; upland woods, woodland edges|
|Plant height:||1 to 3 feet|
|Wetland Indicator Status:||GP: FACU MW: FACU NCNE: FACU|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Leaves and stems:
At the top of the stem is a whorl of 3 leaves (fronds), each 2 or 3 times compound and generally triangular in outline. The leaf blade is 2 to 4 feet long and 1 to 3 feet wide. The leaves are held nearly erect to almost horizontal, parallel to the ground.
The shape of the leaflets varies, with 10 to 12 pair of deeply lobed segments that are oblong to narrowly triangular; segments may be further lobed. Veins are forked. Leaf and leaflet stalks (rachis) are green but turn dark brown later in the season, are slightly grooved, and may have miniscule rough hairs. The main stem (stipe) is brown near the base and covered in short hairs
Spores develop in mid to late June on the underside of the leaves in a continuous narrow band along the leaf edge, though the rolled edges may cover them. Spores may persist through late summer. There is no significant difference between fertile and sterile fronds.
Bracken fern is very common and tends to form large colonies through underground rhizomes. It is easy to identify as it is a relatively large fern with 3 broadly triangular compound leaves, often held horizontally, at the top of a long stem. While the Oak ferns (Gymnocarpium species) also have triangular compound leaves held horizontally, they are much smaller plants, under 16 inches tall, and have round sori (spore clusters) at vein tips. Bracken releases allelopathic chemicals that inhibit the growth of other plants and contains other toxins that are poisonous to many animals. It is the first plant to be killed by frost but will resprout quickly after a fire and can be weedy. An abundance of Bracken is usually indicative of a degraded habitat. There are 4 varieties of Bracken in North America, with var. latiusculum found in Minnesota.
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Photos by K. Chayka taken in Ramsey County. Photos courtesy Peter M. Dziuk taken in Anoka County.
Have you seen this plant in Minnesota, or have any other comments about it?