Weeds L2 Flashcards
example of person - place - time
person - dandelions in lawn
place - volunteer crops (or time)
time - kochia
ecology weed definition
a plant that forms populations and enters habitats cultivated, disturbed, or occupied by man and can depress or replace resident populations which are cultivated or are of ecological and/or aesthetic value
Agricultural weed defintion
any plant not intentionally sown or propagated by the grower that requires management to prevent it from interfering with crop or livestock production
allelopathy
the positive and negative effects of plants on other organisms through chemical substances
how do plants communitcate
above ground via volatiles
below ground via root exudates
plant volatiles
chemicals that plants release into the air
root exudates
chemicals exuded by roots of growing plants
kin recognition
plants recognize if there is the same species next to them or if it is an alternate species
how does kin recognition affect crops
crops have been bred to be less competitive with neighbors, which means that the presence of non-kin species can reduce yields
Example of kin recognition
rice does not exude chemicals when next to rice, but produces more root excretes when next to a different species
Potential strategy with kin recognition for improve weed management
make crops more competitive against weeds
How are weeds classified?
habitat
structure and appearance/taxonomic relation
life cycle
origin
Types of weed habitats
cropland, rangeland, forests, aquatic, and environmental weeds
Example of weeds in forests
Scotch broom in British Columbia
Example of weed in pastures
Nodding thistle - cattle don’t eat it
Example of aquatic weed
Water Hyacinth - can completely clog waterways and make water inhabitable
Suffix of most weeds
aceae
How are weeds classified through structure and appearance?
Monocotyledons and dicotyledons
monocotyledon
one cotyledon
dicotyledons
2 cotyledons
Types of monocotyledons
grasses, sedges, and rushes
Types of dicotyledons
broadleaf plants
grasses (poaceae)
annual of perennial
narrow, parallel-veined leaves
circular jointed stems that are hollow at internodes
sedges (cyperaceae)
perennial grass-like plants that are common in wet, poorly drained soils
triangular, non-jointed stem that is solid
rushes
annual or perennial plants that look similar to sedges
grass-like tufted leaves
circular, non-jointed stems that are hollow
ferns
primitive perennial plants that do not produce flowers/seeds and reproduce by long rhizomes or spores
consist of leaf/frond and a stalk
Branken weed
causes sickness and death in livestock
Types of life cycles
Summer annual
Winter annual
biennials
perennials
types of perennials
simple and creeping
summer annuals
germinate in spring, mature, produce seeds, and die in the fall (1 growing season)
most common type of weed in annually tilled fields
examples of summer annual weeds
giant foxtail, smooth pigweed, common lambs quarters
winter annual
germinate in late summer/fall, mature, produce seeds, and then die the following spring/summer
problem in fall seeded crops, early spring grains, pastures, and no-till fields
Winter annual weed examples
common chickweed, downy brome, annual bluegrass
biennials
grow from seed anytime during the growing season, usually producing rosette first year, then flower, mature, and die second season
Problem in no-till, pastures
Examples of biennial weeds
wild carrot, bull/must thistle, poison hemlock
perennials
live more than 2 years
problem in no-till, pastures, roadsides, and row crops
simple perennial
form a deep taproot and spread primarily by seed dispersal
Example of simple perennial
dandelion, common pokeweed
creeping perennial
either herbaceous or woody and can spread by both vegetative structures and seed
Examples of creeping perennial (herbaceous and woody)
Herbaceous - canada thistle, common milkweed, common purslane
Woody - poison ivy, bamboo, brambles
Why do you have more problems with perennials with more tillage?
you spread the vegetative parts around
Examples of parasitic weeds
mistletoe, broomrape, dodder
How is mistletoe parasitic
birds eat berries and clean beak on trees to get rid of sticky seed. Grows on trunk and gets nutrients from host plant (can photosynthesize
How is broomrape parasitic
Will germinate and connect to host plant with roots (cant photosynthesize)
How is dodder parasitic
germinates in-ground and finds host plant to grab onto. will spread to other plants when host plant dies
Types of weed origins
Native
non-native/exotic/alien
Native weeds
occur naturally in a place without human intervention
non-native weeds
introduced to an area by people from other contents, states, ecosystems, or habitats
Examples of weed species native to North America
Annual sunflower, common plantain, canada fleabane, bluebur, field horsetail, foxtail barley, giant ragweed
Examples of alien weeds from Europe or eurasia
Green foxtail, wild oat, wild buckwheat, lambs quarters, canada thistle, dandelion
invasive species
cases when exotic species aggressively displace native species and reduce land value
common characteristics of invasive weeds
fast growth
rapid reproduction
high seed production and dispersal ability
tolerance to lost of environmental conditions
aggressive and prolific vegetative reproduction
association with humans/human activities
example of invasive weeds in Canada
Canada thistle (perennial)
Garlic Mustard
Slender foxtail
