Dryopteris expansa

Safety & Hazards

Although we have found no reports for this species, a number of ferns contain carcinogens so some caution is advisable[ 200 Title The New RHS Dictionary of Gardening. 1992. Publication Author Huxley. A. Publisher MacMillan Press Year 1992 ISBN 0-333-47494-5 Description Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed. ]. The fresh plant contains thiaminase, an enzyme that robs the body of its vitamin B complex. In small quantities this enzyme will do no harm to people eating an adequate diet that is rich in vitamin B, though large quantities can cause severe health problems. The enzyme is destroyed by heat or thorough drying, so cooking the plant will remove the thiaminase[ 172 Title Discovering Wild Plants - Alaska, W. Canada and the Northwest. Publication Author Schofield. J. J. Publisher Alaska Northwest Books; Alaska Year 2003 ISBN 0882403699 Description A nice guide to some useful plants in that area. ]. However, there have been reports for other species of ferns suggesting that even cooked fronds can have a long term harmful effect. Some caution is therefore advised.