Transcript Weeds

Weeds in the
Landscape
WEED LIFE CYCLES
Annuals: begin season as seed and finish
life cycle in one year
 Produce massive amounts of seed
Summer Annual

Germinate in spring and die in winter
WEED LIFE CYCLES
Annuals: begin season as seed and finish
life cycle in one year
– Produce massive amounts of seed
Winter Annual

Germinate in fall, die in summer
WEED LIFE CYCLES
Biennial: 2 growing seasons
 First season—vegetative parts
 Second season – flowers and seeds
WEED LIFE CYCLES
Perennials: live 3 years or more
 Die back to ground in winter and regrow
from roots, tubers, rhizomes, or stolons
 Limited seed
WEED LIFE CYCLES
Perennials
 Difficult to control because of
underground portions
WEED GROWTH HABIT
Grassy: true grasses
 Perennial or annual
WEED GROWTH HABIT
Broadleaf: (mostly) wide leaves
WEED GROWTH HABIT
Non-grass
 Sedge, rushes, onion and garlic
DESIGN TO AVOID WEEDS
Plant selection
 Less affected by weed competition
DESIGN TO AVOID WEEDS
Edging
 Borders that restrict invasion
DESIGN TO AVOID WEEDS
Drip irrigation
 Avoid providing water to weeds
DESIGN TO AVOID WEEDS
DESIGN TO AVOID WEEDS
DESIGN TO AVOID WEEDS
Competitive plants
 Dense canopies shade out bare ground
SITE PREPARATION
Eliminate established weeds
SITE PREPARATION
Cultivation
 Rototilling
SITE PREPARATION
Solarization
 Tarping soil to retain sun’s heat and
destroy weeds seeds
 Can also reduce disease and nematode
SITE PREPARATION
Solarization
 Cover with clear plastic
 Seal edges for greenhouse effect
 Cover 4 to 6 weeks
 Avoid bringing up soil deeper than 3”
SITE PREPARATION
Weed fabric
 Breathable fabric
 No plastic
Pittosporum (4 years)
 Mulch only

Mulch + 1 application of
preemergent herbicide

Mulch + weed fabric
SITE PREPARATION
Mulch
 Prevention of annual weed germination
 Excludes light
 Moisture retention
 Soil temperature stabilizer
 Enrich soil
SITE PREPARATION
Organic mulch
 Bark
 Shredded mulch
 Pine straw
SITE PREPARATION
Inorganic mulch
 Stone
 Recycled rubber
 Synthetic pine straw
SITE PREPARATION
Organic mulch
 Maintain 2 to 4” deep
 Keep away from base of plants about 1’
from trunk
CONTROL ESTABLISHED WEEDS
Preventing seed introduction
 Wash equipment
 Avoid contaminated stock
CONTROL ESTABLISHED WEEDS
Cultivation – avoid under trees
 Disturbs roots
 Won’t effect vegetative weeds
– dollarweed
CONTROL ESTABLISHED WEEDS
String trim
 Avoid hitting trunk
CONTROL ESTABLISHED WEEDS
String trim
 Mulch to avoid damage to trunk
 Tree guard
CONTROL ESTABLISHED WEEDS
Flaming
 Torch base of plant, disrupt cells
 Primarily annuals
CONTROL ESTABLISHED WEEDS
Herbicides

Fumigants kill everything in soil
CONTROL ESTABLISHED WEEDS
Herbicides
Pre-emergent: kill germinating weeds for
several weeks
 Must be applied before germination
CONTROL ESTABLISHED WEEDS
Herbicides
Post-emergent: kill weeds already
germinated
 Most effective on young, vigorously
growing weeds
CONTROL ESTABLISHED WEEDS
Postemergent Herbicides
Contact versus Systemic
Contact: kills only green parts that are
sprayed
 Quick kill
 No underground kill

2 hours
24 hours
CONTROL ESTABLISHED WEEDS
Postemergent Herbicides
Contact versus Systemic
Systemic: translocated to roots and
growing tips
 Good on perennial weeds
 During vigorous growth

– Round-up and N

May take a few days to a few weeks
CONTROL ESTABLISHED WEEDS
Postemergent Herbicides
Selective versus Non-selective

Selective: only certain types of plants
affected
– Broadleaf only
– Grassy only
CONTROL ESTABLISHED WEEDS
Postemergent Herbicides
Selective versus Non-selective

Non-selective: kills everything that is
sprayed