Weeds Friends or Foes: Weeds Friends or Foes By Danny Silva
April 2001 Core Area (CLF300) Plant Science
Unit (CLF360) Pest Management
Topic (CLF) Weed Collections What Do YOU Think?: What Do YOU Think? 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 made to the landscape by man or nature. Don’t let Weeds Ruin Your Crops!: Don’t let Weeds Ruin Your Crops! 3. Weeds reduce crop yields and increase the cost of producing crops.
4. Some weeds are poisonous and others may cause allergies. Don’t let Weeds Ruin Your Day!: Don’t let Weeds Ruin Your Day! a. For a farmer or gardener to do an effective job of controlling troublesome weeds, exact identification of the weed pest is important.
b. The selection of the most effective control method depends on one’s ability to properly identify the problem pest species. Identification is the Key: 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 to identify some common weeds is to compare your specimens with drawings and colored photographs using references such as those listed at the beginning of this unit. Use Those Resources: Use Those Resources a. The use of weed keys such as those found in field guides and references do require specialized knowledge of weeds
b. Specialists like farm advisors, agriculture commissioners, or college or university agriculture staffs can be contacted for help in identifying plant species. Weed Classification: Weed Classification 2. 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 and broad leafed.
1) Narrow leafed weeds include grasses, sedges, rushes and cattails, which all have parallel veins in their leaves.
2) Broad leafed weeds include most others such as mustards, dock, pigweed, purslane and morning glory, all having net-like pattern of veins in the leaves. “Live Long and Prosper”: “Live Long and Prosper” 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, and
3) perennial weeds live for 3 or more years. What’s Your Name?: What’s Your Name? c. Weeds and most other plants have unique physical features which can be used for identification.
1) Flowers and certain sexual reproductive organs very among species.
a) To use flowers as an aid to identification you need to familiar with the different flower parts.
b) Flowers appear singly or as compound inflorescence.
c) Different names such as catkin, head, panicle,raceme, spike, and umbel describe how flowers are arranged in an inflorescence.
d) The arrangement, shape, vein patterns and presence of hairs or spines are noted differences in leaves.
e) Stem variations such as rhizomes, stolons, and tubers are helpful to help identify some species.
f) Taproots of the broad leafed weeds will separate them from the fibrous roots of grasses.
g) Fruits and seeds are all unique in their shape, size, markings and color. Ah! A Baby Weed: Ah! A Baby Weed 3. It is especially helpful to be able to identify weeds while they are in the cotyledon stage (one of a pair of the first leaves from a sprouting seed…also called a “seed leaf”).
a) The weed can be controlled before it competes with crop plants.
b) Usually control measures are more effective and less costly when weeds are treated at an immature stage of their life cycles. A Chance to Practice: A Chance to Practice The following 25 slides are of some common weeds.
The first line is a common name.
The second line the scientific name.
Third line tells the life cycle.
The fourth line is the growing season. Annual
Cool season Slide12:
Cool season Slide13:
cool season) Slide14:
Warm season Slide15:
Warm season Slide16:
Cool season Slide21:
Cool season Slide23:
Cool season Slide25:
Cool season Slide27:
Warm season Slide28:
Cool season Slide31:
Warm season Slide32:
Warm season Slide33:
Cool season Slide34:
Cool season Slide35: