Weeds: Friends or Foes

1
Weeds Friends or Foes?

• Original Power Point Created by
• Danny Silva

Modified by the GA Agricultural Education
Curriculum Office July 2002
2
Weeds Benefits

• Weeds are controversial plants that are neither
  all good nor all bad, depending on ones 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.

3
Harmful Weeds

• 1. Weeds reduce crop yield and increase the
  cost of production.
• 2. Some weeds are poisonous and others may cause
  allergies.

4
Dont 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 ones ability to properly
  identify the problem species.

5
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.

6
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.

7
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.

8
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.

9
Whats 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.

10
Whats 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.

11
The Cotyledon Stage

• III. It is especially helpful to identify weeds
  while they are in the cotyledon stage because
• 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.

12
A Chance To Practice

• IV. The following 25 slides are examples of
  several common weeds
• 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.

13
Annual Bluegrass Poa Annua Annual Cool season
14

Bermuda Grass Cynodon dactylon Perennial Dorm
ant in the cool season
15
Bristly Oxtongue Picris echioides Biennial
16
Broadleaf Plantain Plantago major Perennial
17
Bur Clover Medicago polymorpha Annual Cool
season
18
Cheeseweed or Mallow Malva parviflora Biennel
19

Common Goundsel Senecio vulgaris Annual Cool
season
20
Crabgrass Digitaria ischaemum Annual Warm
season
21
Cudweed or Cotton Batting Gnaphalium
chilense Biennial
22
Curly Dock Rumex crispus Perennial
23

Dandelion Taraxacum officinale Perennial
24
Fennel Foeniculum vulgare Perennial
25
Filaree Erodium spp. Annual Cool season
26
Knotweed Polygonum aviculare Annual Warm
season
27
Lambsquarters Chenopodium album Annual Warm
season
28
Narrowleaf Plantain Plantago
lanceolata Perennial
29
Oxalis Oxalis spp. Perennial
30
Petty Spurge Euphorbia peplus Annual Cool
season
31
Prostrate Spurge Euphorbia maculata Annual Wa
rm season
32
Purslane Portulaca oleraceae Annual Warm
season
33
Scarlet Pimpernel Anagallis arvensis Annual C
ool season
34
Shepherds Purse Capsella bursa-pastons Annua
l Cool Season
35
Sow Thistle Sonchus oleraceus Annual Cool
season
36
Yellow Mustard Brassica species Annual Cool
season
37
Yellow Nutsedge Cyperus esculentus Perennial