Original Power Point Created by Danny Silva Weeds: Friends or Foes? Original Power Point Created by Danny Silva Modified by the GA Agricultural Education Curriculum Office July 2002

Weeds: Benefits 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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

Annual Bluegrass Poa Annua Annual Cool season

Bermuda Grass Cynodon dactylon Perennial Dormant in the cool season

Bristly Oxtongue Picris echioides Biennial

Broadleaf Plantain Plantago major Perennial

Bur Clover Medicago polymorpha Annual Cool season

Cheeseweed or Mallow Malva parviflora Biennel

Common Goundsel Senecio vulgaris Annual Cool season

Crabgrass Digitaria ischaemum Annual Warm season

Cudweed or Cotton Batting Gnaphalium chilense Biennial

Curly Dock Rumex crispus Perennial

Dandelion Taraxacum officinale Perennial

Fennel Foeniculum vulgare Perennial

Filaree Erodium spp. Annual Cool season

Knotweed Polygonum aviculare Annual Warm season

Lambsquarters Chenopodium album Annual Warm season

Narrowleaf Plantain Plantago lanceolata Perennial

Oxalis Oxalis spp. Perennial

Petty Spurge Euphorbia peplus Annual Cool season

Prostrate Spurge Euphorbia maculata Annual Warm season

Purslane Portulaca oleraceae Annual Warm season

Scarlet Pimpernel Anagallis arvensis Annual Cool season

Shepherd’s Purse Capsella bursa-paston’s Annual Cool Season

Sow Thistle Sonchus oleraceus Annual Cool season

Yellow Mustard Brassica species Annual Cool season

Yellow Nutsedge Cyperus esculentus Perennial