Last of the Spring Bad Actors-Garlic Mustard!

Alliaria petiolata (garlis mustard) bud

Garlic mustard seedlings

Garlic mustard (Alliaria petiolata) is a biennial, appearing as a rosette of leaves it’s first year and flowering its second. An easy test is to crush the leaves; garlic mustard will smell like garlic. It appears mostly in disturbed forest edges but is quite capable of spreading thickly and becoming dominate in the forest understory. Like other invasives, it has the triple whammy of an early spring appearance, few native enemies and lots and lots and lots of seeds.Around here, we find it follows the flow of water. After a flood or major rain event, you’ll find batches of seeds sprouting where they were dropped.

Generally we have hand pulled, and you’ll often find “garlic mustard pull” events organized by your neighborhood conservation organization. Since they are biennial, chopping off the flower heads with a weed eater before they go to seed is another option we have tried. The seeds remain viable in the seed bank for up to five years, so you have to keep at it.

You’ll read lots of terrifying descriptions of the impact of garlic mustard in the woods: According to the NYS Invasive Species website,  garlic mustard is “…one of the worst invaders of forests in the American Northeast and Midwest…recent findings have shown that garlic mustard has the ability to establish and spread even in pristine areas. This spread has allowed it to become the dominant plant in the undergrowth of some forests, greatly reducing the diversity of all species. ”

HOWEVER, I have read (and heard) from several folks involved with Cornell Botanic Gardens natural areas that they no longer pull garlic mustard as a general rule. This is so interesting to me, I am going to quote here an entire article on why not I gleaned from the NYSFOA newsletter. Enjoy!

NYFOA Southern Fingerlakes Chapter
May 2018

Garlic mustard management update
Dr. Bernd Blossey, Cornell University,
Ithaca, NY 14853, (bb22@cornell.edu)
Background: Garlic mustard (Alliaria
petiolata) was once considered one of the most
problematic plant invaders in eastern temperate
forests. Declines in native plant species diversity and
deterioration in general forest health were attributed
to advancing garlic mustard. The lack of success in
controlling the species resulted in the initiation of
research todevelop a biological control program.
While ecological investigations were pursued,
chemical, and often physicalremoval programs
continued (including “garlic mustard challenges”). At
the same time researchers established longterm
permanent monitoring plots in preparation for
potential insect releases. In these plots the abundance
ofseedlings, rosettes and adult stems, stem height,
reproductive output and herbivory were recorded.
New Evidence
Monitoring of garlic mustard at
many sites across the Northeast and Midwest in these
permanent plots has shown that over time adult
density, rosette density, stem height and the number
of siliques is greatly reduced to an extentwhere garlic
mustard, while present, is reduced to extremely low
abundance. These results occur at all sites.
Additional work using soil sterilization has shown
that these effects are, most likely, explained by
negative soilfeedback, i.e. the build-up of soil
microbial communities that selectively suppress
garlic mustard (other plant speciesappear unaffected).
We are currently preparing these results with our
collaborators for publication in the peerreviewed
literature.Recommendations We are aware that many
organizations and communities are gearing up for
another season of garlic mustard removal,often
dubbed “garlic mustard challenges”. The most recent
ecological work has shown that effects attributed to
garlic mustard invasion are more likely effects of
invasive earthworms and abundant native white-
tailed deer. Garlic mustard will only be able to invade
and establish populations in areas, which have been
colonized by earthworms.Removing garlic mustard
will not help to restore thriving native communities.
In fact, removing garlic mustard will set back the
“self-inflicted” population declines by preventing
negative soil feedback. Only in places where garlic
mustard is not controlled will the species decline
rapidly (often within 5-10 years after initial invasion,
but moreobservations are needed). We recommend
stopping all active garlic mustard removal (unless
initial invasions can bestopped by removing a few
individuals away from well-established populations)
and instead focusing on plantingnative species.
Native species will need to be protected from deer
herbivory behind fences or in cages until deer
populations are sufficiently reduced. Please be aware
that garlic mustard will continue to spread to areas
where thespecies has not occurred previously. The
decline in population and vigor is a function of
residence time.

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