Weeds in the Landscape

WEED LIFE CYCLES Annuals: begin season as seed and finish life cycle in one year Produce massive amounts of seed Produce massive amounts of seed Summer Annual Germinate in spring and die in winter 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 Germinate in fall, die in summer

WEED LIFE CYCLES Biennial: 2 growing seasons First season—vegetative parts First season—vegetative parts Second season – flowers and seeds 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 Die back to ground in winter and regrow from roots, tubers, rhizomes, or stolons Limited seed Limited seed

WEED LIFE CYCLES Perennials Difficult to control because of underground portions Difficult to control because of underground portions

WEED GROWTH HABIT Grassy: true grasses Perennial or annual Perennial or annual

WEED GROWTH HABIT Broadleaf: (mostly) wide leaves

WEED GROWTH HABIT Non-grass Sedge, rushes, onion and garlic Sedge, rushes, onion and garlic

DESIGN TO AVOID WEEDS Plant selection Less affected by weed competition Less affected by weed competition

DESIGN TO AVOID WEEDS Edging Borders that restrict invasion Borders that restrict invasion

DESIGN TO AVOID WEEDS Drip irrigation Avoid providing water to weeds Avoid providing water to weeds

DESIGN TO AVOID WEEDS

Competitive plants Dense canopies shade out bare ground Dense canopies shade out bare ground

SITE PREPARATION Eliminate established weeds

SITE PREPARATION Cultivation Rototilling Rototilling

SITE PREPARATION Solarization Tarping soil to retain sun’s heat and destroy weeds seeds Tarping soil to retain sun’s heat and destroy weeds seeds Can also reduce disease and nematode Can also reduce disease and nematode

SITE PREPARATION Solarization Cover with clear plastic Cover with clear plastic Seal edges for greenhouse effect Seal edges for greenhouse effect Cover 4 to 6 weeks Cover 4 to 6 weeks Avoid bringing up soil deeper than 3” Avoid bringing up soil deeper than 3”

SITE PREPARATION Weed fabric Breathable fabric Breathable fabric No plastic No plastic

Pittosporum (4 years) Mulch only Mulch only Mulch + 1 application of preemergent herbicide Mulch + 1 application of preemergent herbicide Mulch + weed fabric Mulch + weed fabric

SITE PREPARATION Mulch Prevention of annual weed germination Prevention of annual weed germination Excludes light Excludes light Moisture retention Moisture retention Soil temperature stabilizer Soil temperature stabilizer Enrich soil Enrich soil

SITE PREPARATION Organic mulch Bark Bark Shredded mulch Shredded mulch Pine straw Pine straw

Inorganic mulch Stone Stone Recycled rubber Recycled rubber Synthetic pine straw Synthetic pine straw SITE PREPARATION

Organic mulch Maintain 2 to 4” deep Maintain 2 to 4” deep Keep away from base of plants about 1’ from trunk Keep away from base of plants about 1’ from trunk

CONTROL ESTABLISHED WEEDS Preventing seed introduction Wash equipment Wash equipment Avoid contaminated stock Avoid contaminated stock

CONTROL ESTABLISHED WEEDS Cultivation – avoid under trees Disturbs roots Disturbs roots Won’t effect vegetative weeds Won’t effect vegetative weeds –dollarweed

CONTROL ESTABLISHED WEEDS String trim Avoid hitting trunk Avoid hitting trunk

CONTROL ESTABLISHED WEEDS String trim Mulch to avoid damage to trunk Mulch to avoid damage to trunk Tree guard Tree guard

CONTROL ESTABLISHED WEEDS Flaming Torch base of plant, disrupt cells Torch base of plant, disrupt cells Primarily annuals Primarily annuals

CONTROL ESTABLISHED WEEDS Herbicides Fumigants kill everything in soil Fumigants kill everything in soil

CONTROL ESTABLISHED WEEDS Herbicides Pre-emergent: kill germinating weeds for several weeks Must be applied before germination Must be applied before germination

Edging Borders that restrict invasion Borders that restrict invasion

CONTROL ESTABLISHED WEEDS Herbicides Post-emergent: kill weeds already germinated Most effective on young, vigorously growing weeds Most effective on young, vigorously growing weeds

CONTROL ESTABLISHED WEEDS Postemergent Herbicides Contact versus Systemic Contact: kills only green parts that are sprayed Contact: kills only green parts that are sprayed Quick kill Quick kill No underground kill No underground kill

2 hours

24 hours

CONTROL ESTABLISHED WEEDS Postemergent Herbicides Contact versus Systemic Systemic: translocated to roots and growing tips Systemic: translocated to roots and growing tips Good on perennial weeds Good on perennial weeds During vigorous growth During vigorous growth –Round-up and N May take a few days to a few weeks 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 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 Non-selective: kills everything that is sprayed