wmw was correct back in his original posting. The material used in thatching depends on the part of the world being described. Therefore, context
is of paramount importance.http://en.wikipedia.org/wiki/Thatching
Although thatch is popular in Germany, The Netherlands, Denmark, Belgium and Ireland, there are more thatched roofs in the United Kingdom than in any other European country. Good quality straw
thatch can last for more than 50 years when applied by a skilled thatcher. [...] Over 250 roofs in Southern England have base coats of thatch that were applied over 500 years ago, providing direct evidence of the types of materials that were used for thatching in the medieval period. Almost all of these roofs are thatched with wheat, rye, or a 'maslin' mixture of both
. Medieval wheat grew to almost 6 feet (1.8 m) tall in very poor soils and produced durable straw
for the roof and grain for baking bread.
All of the evidence indicates that water reed
was rarely used for thatching outside of East Anglia. [...]
In areas where palms are abundant, palm leaves
are used to thatch walls and roofs. [...]
EDIT: It appears wmw has made up a sentence for his OP from something else he has read.
EDIT 2: BBC article from 10 years ago: http://www.bbc.co.uk/insideout/southwest/seri...