Vol. 54—2000 - NorthEastern Weed Science Society

HERBICIDE APPLICATIONS VERSUS HANDWEEDING HERBACEOUS PERENNIAL PLUGS:
POTENTIAL FOR CROP DAMAGE AND CROP LOSS
AnnamariePennucciI
ABSTRACT
Handweeding and one-time herbicide applications were evaluated for their relative effectiveness
in reducing weed populations indigenousto herbaceous perennialplant production. Commerciallyavailableherbaceous
plugs, weed infested during propagation and prior to receipt, were
transplanted into finishing4 inch pots and weed and crop growth evaluated. Crop plants were
grouped into categories by leaf sizeand the effectivenessof weed control measureswas evaluated
during the season. Handweeding smalland mid-sizedcrops resulted in greater crop damage and loss
than herbicideapplications despite the relative ineffectivenessof post-emergent applications of broad
spectrum herbicides.Handweeding large-sized crops resulted in greater crop densities and greater
weed control than post-emergent applications but handweeding efforts had to be repeated to maintain
that effectiveness. Handweeding followed by pre-emergent applications offers the best compromise
between potential crop loss and weediness.
INTRODUCTION
The production of herbaceous perennial ornamental plants for both wholesale and retail sales
in the Northeast typically begins with the importation of dormant or near-dormant plugs from large
mid-western propagators. Plug sizes may vary from an average minimum 3/4 inch to an average
maximum 2.25 inch diameter and plugs may bebare-root, in soil or sphagnum or produced in
variously sized trays. For most retail sales, dormant plugs are received in late winter/early spring and
transplanted to the final pot sizes and "grown-on" in cool greenhouses, unheated hoop houses, under
shade clothes, on landscape fabric, or directly on sales benches.
In recent years, numerous complaints have been made concerning the receipted condition of
these plugs; with especial emphasis placed on their "weediness". In various circumstances, weed
growth resumed in advance of crop growth; concommitant with crop growth or followed but later
overshadowed crop growth. The greatest severity of complaint concerned those weeds that outgrew
the crop to the extent that the crop could not bedistinguished from the weeds or was lost completely.
MATERIALS
AND METHODS
A brief survey was taken to determine which species of herbaceous perennials plugs were
most likely to harbor weeds and if the expected size of the crop influenced, in any way, the severity of
weed interactions. The weed species most commonly encountered were determined and the
proportion of the crop lost when weed control measures were not taken was estimated. Weed control
efforts were initiated on two crops each of three different size categories; control efforts included
handweeding and one-time herbicide applications.
Handweeding was evaluated at plug planting by counting and identifying weed populations as
nursery employees removed them; the size of the remaining plug was estimated. Pots were placed in a
special holding area that maintained the normal nursery regime (irrigation, fertilization) and weeds
counts were made I, 2, 4 and 8 weeks after planting (wap).
, Northeast Turf and Ornamental Research, Raymond. N.H. 03077
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