Vol. 54—2000 - NorthEastern Weed Science Society

POTENTIAL WEEDINESS OF SEVERAL NEW HERBACEOUS PERENNIAL CROPS
Annamarie Pennucci I
ABSTRACT
A brief review of new herbaceous perennial crops indicates that several have already
demonstrated the potential for intra- and inter-nursery spread. A list of potential nursery crops that
may act as invasive weeds follows. An analysis of morphological factors that predispose these crops
to act as weeds and a description of potential factors to consider prior to crop release is suggested.
INTRODUCTION
During the past two seasons, several New Hampshire nurseries and farm stands reported the
unexpected spread of novel crop plants into pots and containers of both woody and herbaceous plant
materials. Such unwelcome movement within the nursery compromised plant identity. plant health and
the economic requirement for weed free status, Consequently, questions arose concerning the
necessity of crop cleanliness, recognition and hand removal of one of the crop plants, using herbicides
to prevent further ingress, and separation or containment to prevent further spread of seemingly
desirable species.
Several of these plants are newly developed or selected for the herbaceous perennial trade and
while some are closely related to or cultivars of existing crop or weed species, others are new genera
whose potentials as crop or weed remains unknown.
MATERIALS AND METHODS
Two nurseries located in southern New Hampshire first reported the appearance of unusual
plants in purchased containers as early as 1997. Both nurseries obtained plant materials from several
of the same mid-western plug propagators and from the same two in-state perennial plant wholesalers.
Both nurseries were surveyed monthly in 1998 and 1999 for unusual weeds and those weeds
were identified according to both standard references and new crop catalogues.
Movement of these novel crops/weeds (cw) within the nursery was measured in linear feet
from the original source plants to other plants held in stock areas, in feet and in acres from stock to
sales tables and in total acres across the nursery. Morphological traits that might account for
movement were determined and the number of pots within each crop species infested with cw was
counted monthly. Herbaceous perennial crop plants were categorized by the amount of soil visible at
maturity and the relative strength of the crop and the number of crop plant units invaded in each
category was determined.
Industry standard herbicides were used at label rate in each of these nurseries. Typically,
Dacthal (DCPA [dimethyl 2,3,5,6-tetrachloro-I,4-benzenedicarboxylate]) was applied as the crop
resumed spring growth at preemergence and 10 weeks later as a postemergent drench; Preen
(pendimethalin [N-(I-ethylpropyl) -3,4-dimethyl-2,6-dinitrobenzeneamine] applied preemergent and 8
weeks later as a postemergent drench; Gallery (isoxaben [N-[3-(I-ethyl-I-methylpropyl)-S-isoxazolyl]
-2,6-dimeth- oxybenzamide] applied preemergent and Scotts OH-2 (pendimethalin + oxyfluorfen
[2-chloro-I-(3-ethoxy-4- nitrophenoxy)-4-(trifluoromethyl)benzene] applied pre/post as crop growth
resumed. Herbicidal efficacy on cw was determined 6 and 16 weeks after finaltreatment.
I Northeast Turf andOrnamental Research. Raymond, N.H. 03077
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