www.urban-forestry.com 19
The plant has its own reasons for making resver-
atrol—it's a part of knotweed's defense system.
Resveratrol is a phytoalexin, a compound produced
in the tissues of the plant in response to microbial
attack. Though the evidence for resveratrol's effects
on human health is unsubstantiated, research in
the agricultural realm has found extract of Japanese
knotweed to be an effective antifungal agent, pro-
tecting crops such as tomatoes, wheat, and cucum-
bers from various fungal diseases—most notably,
powdery mildew, gray mold, and rust. Knotweed's
naturally-induced phytoalexins inhibit the formation
of spores in pathogenic fungal species, and the
extract, when sprayed on certain crops, confers the
same benefit. As it is plant-based and minimally
toxic to mammals, is considered safe for organic
farming by the National Organic Program, and is
marketed in the U.S. under the trade name Regalia.
Invading marauder, life-extending miracle powder, lit-
eral home-wrecker, organic farmer's friend ... Japanese
knotweed deserves one more public reputation: first
responder. In its native habitat, the volcanic slopes of
Japan, it has long played that role. It is the first plant to
appear after the lava has flown. There it colonizes the
bare rock and slowly builds soil, allowing other species
to return. When it appears in habitats disturbed by
humans, as it has all over Europe and North America,
it is only following its tenacious nature. And for that it
deserves, at least, some respect.
