Download Weeds Friends or Foes

Weeds: Friends
or Foes?
Original Power Point Created by
Danny Silva
Modified by the GA Agricultural Education Curriculum Office
July 2002
August 2008
Weeds: Benefits
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Weeds are controversial plants that are neither
all good nor all bad, depending on one’s outlook.
1. Many weeds can be enjoyed for their
attractive flowers and interesting seed pods.
2. Weeds quickly grow
to cover unsightly scars
on the landscape made
by man or by nature.
August 2008
Harmful Weeds
• 1. Weeds reduce crop yield and increase
the cost of production.
• 2. Some weeds are poisonous and others
may cause allergies.
August 2008
Don’t Let Weeds Ruin Your Day!
For a farmer or gardener to do an effective job of
controlling troublesome weeds, exact identification
of the weed is important.
The selection of the most effective control method
depends on one’s ability to properly identify the
problem species.
August 2008
Identification Is The Key
• The purpose of a weed
collection is to help the
person making the
collection more adept at
identifying weeds:
• 1. A simple way to begin
identifying common
weeds is to compare
your specimens against
drawings and colored
photographs from
references.
August 2008
Identification Is The Key
(cont.)
a. The use of weed keys, such as those
found in field guides and references,
do require a specialized knowledge of
weeds.
b. Specialists like farm advisors,
agricultural commissioners, or
college/university faculty can be
contacted for help with identifying
plant species.
August 2008
Weed Classification
• II. The classification of weeds is achieved
by grouping together those weeds whose
similarities are greater than their
differences.
a. Most weeds can be placed into two
convenient groups: narrow-leafed or
broad-leafed.
• 1) Narrow-leafed weeds include: grasses, sedges,
rushes and cattails. All have parallel veins running
throughout their leaves.
• 2) Broad-leafed weeds include: most others, such as
mustards, dock, pigweed, purslane, and morning glory.
All have a net-like pattern of veins running throughout the
leaves.
August 2008
Weed Classification (cont.)
b. Like other plants, weeds have varying types of life
cycles:
• 1) Annual weeds live for one year or less.
• 2) Biannual weeds live for two growing seasons.
• 3) Perennial weeds live for 3 or more years.
August 2008
What’s Your Name?
c. Weeds have unique physical features
which can be used for identification.
• 1) Flowers and certain sexual
reproductive organs vary among
species:
a) Flowers can appear singly or as a compound
inflorescence.
b) Different names such as catkin, head, panicle, raceme,
spike, and umbel describe how flowers are arranged in
an inflorescence.
c) The arrangement, shape, vein patterns, or presence of
hairs/spines on leaves may vary between species.
August 2008
What’s Your Name? (cont.)
d) Stem variations
such as rhizomes,
stolons, and tubers
are helpful in
identification.
e) Taproots of the
broad-leafed
weeds differentiate
them from the
fibrous roots of
grasses.
f) The fruits and
seeds of weeds
are all unique in
their shape, size,
markings, and
color.
August 2008
The Cotyledon Stage
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III. It is especially helpful to identify
weeds while they are in the cotyledon
stage because:
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a. The weed can be controlled before it
competes with the crops.
b. Control measures are more effective and
less costly when the weeds are treated
during this immature stage of their life cycle.
August 2008
A Chance To Practice
• IV. The following 25 slides are examples of
several common weeds:
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August 2008
The first line is the common name.
The second line is the scientific name.
The third line gives the life cycle.
The fourth line is the growing season.
Annual Bluegrass
Poa Annua
Annual
Cool season
August 2008
Bermuda Grass
Cynodon dactylon
Perennial
Dormant in
the cool season
August 2008
Bristly Oxtongue
Picris echioides
Biennial
August 2008
Broadleaf Plantain
Plantago major
Perennial
August 2008
Bur Clover
Medicago
polymorpha
Annual
Cool season
August 2008
Cheeseweed or
Mallow
Malva parviflora
Biennel
August 2008
Common Goundsel
Senecio vulgaris
Annual
Cool season
August 2008
Crabgrass
Digitaria ischaemum
Annual
Warm season
August 2008
Cudweed or
Cotton Batting
Gnaphalium chilense
Biennial
August 2008
Curly Dock
Rumex crispus
Perennial
August 2008
Dandelion
Taraxacum officinale
Perennial
August 2008
Fennel
Foeniculum vulgare
Perennial
August 2008
Filaree
Erodium spp.
Annual
Cool season
August 2008
Knotweed
Polygonum aviculare
Annual
Warm season
August 2008
Lambsquarters
Chenopodium album
Annual
Warm season
August 2008
Narrowleaf Plantain
Plantago lanceolata
Perennial
August 2008
Oxalis
Oxalis spp.
Perennial
August 2008
Petty Spurge
Euphorbia peplus
Annual
Cool season
August 2008
Prostrate Spurge
Euphorbia maculata
Annual
Warm season
August 2008
Purslane
Portulaca oleraceae
Annual
Warm season
August 2008
Scarlet Pimpernel
Anagallis arvensis
Annual
Cool season
August 2008
Shepherd’s Purse
Capsella bursapaston’s
Annual
Cool Season
August 2008
Sow Thistle
Sonchus oleraceus
Annual
Cool season
August 2008
Yellow Mustard
Brassica species
Annual
Cool season
August 2008
Yellow Nutsedge
Cyperus esculentus
Perennial
August 2008