Overview. Teaching Objective. What makes a weed a weed? What makes a weed a weed? What makes a weed a weed? 3/14/2013

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1 Overview Creative Approaches to Weed Management in the Home Garden Dan McGrath Oregon State University Analyze why some plants become weeds and use an ecological approach to developing new control strategies Sort weeds into function groups; the grouping informs our analysis of the problem Learn to manage weeds with herbicides and without herbicides Several small group activities Teaching Objective My teaching objective is to increase your confidence in your ability to analyze a weed problems using an ecological approach. BEFORE WORKSHOP Questionnaire (yellow) What makes a weed a weed? Colonize a disturbed area, grow rapidly, and reproduce Hard seed coat, long lived seeds, variable uneven germination Slowly grow tough perennial root, vegetative propagation, slowly take over Origin Species What makes a weed a weed? Environmental conditions may give the species a competitive advantage moisture, ph, other Disturbance liberates resources nutrients, moisture, light and space What makes a weed a weed? Animals graze selectively giving some species a selective advantage There is nearly always a species that will overcome a given weed control tactics (mulch, rototill, hoe, hand weeding, herbicides, other) 1

2 Question #1 ~ What are the three factors that we should analyze when trying to resolve a weed control problem? Ecological Forces Shape Weed Behavior Slides Disturbance Colonization Competition Succession Controlling access to limiting resources banding, mulch, transplant Filling the space with manageable species Masunobu just like this Managing inter and intra specific competition The parable of the bean rectangulation Filling the space with manageable species Slides: Alternatives to roadside spraying Slides: cover crops, buckwheat, mixed greens, vegetables and flowers in the landscape Managing competition over time Planting in four dimensions Chinese and French Poly Cultures Slides: French and Latin American poly-cultures Slides: Cover crop relay Weed Functional Groups Early colonizers of disturbed sites Winter Annuals Summer Annuals 2

3 Pigweed (Amaranthus sp.) Summer Annuals Lambs quarter (Chenopodium sp.) Bedstraw (Galium sp.) Nightshade (Solanum sp.) Purslane (Portulaca sp.) 3

4 Barnyard Grass (Echinochloa crus-galli) Winter Annuals Shepherd s Purse (Capsella bursa-pastoris) Henbit (Lamium sp.) Groundsel (Senecio sp.) Chickweed (Stelaria sp.) 4

5 Annual Bluegrass (Poa sp.) Weed Functional Groups Late Colonizers of disturbed sites Biennial/Perennial Creeping Perennial Roots Woody/Herbaceous Wild Carrot (Daucus carota) Biennial Weeds Curly Dock (Rumex crispus) Perennial Weeds 5

6 Bindweed (Convolvulus arvensis) Creeping Perennial Weeds Canada Thistle (Cirsium arvense) Nut Sedge (Cyperus sp.) Horsetail (Equisetum sp.) Creeping Bentgrass (Agrostis sp.) 6

7 Blackberry Woody Perennials Scotch Broom Weed Identification Individual effort Books, pictures, web resources Ask other Master Gardeners Ask an Extension Faculty member Send specimen to OSU Herbarium It is generally not necessary to know the genus and species of a weed in order to manage the weed. Worst Weeds in the World Perennials Herbaceous Bent Grass Bind Weed Nut Sedge Horsetail Wild onion and garlic Bamboo Woody Black Berry Poison Oak Scotch Broom Ornamentals English Ivy Oxalis Arum Prevention Get to know them; look for them Potting Soil - nut sedge, oxalis Landscape Soil - horsetail, bind weed, creeping bent grass Compost wild onion Question #2 What is the First Rule of Weed Control Question #3 What is a weed shift? Weed shift describes the situation when a single weed species become highly dominant over a period of time due to environmental conditions or the activities of people. In home gardens, weed shifts generally occur when we apply a single control strategy over and over again. Eventually, a weed species arrives that is resistant to that single strategy, overcomes the strategy and explodes. 7

8 Rotate your control strategies. Mulch Resistant Weeds Tillage resistant Weeds Newman Turner Slides: Herbicide resistance Indonesia paddy rice Fall germinating summer annuals, winter kill and plant into mulch Buckwheat, winter kill, garlic relay Rectangulation, cover crop relay, winter kill, and vetch Herbicides Terminology Systemic Herbicides Specific examples Sugar Flow Herbicide Terminology Acute/Chronic Toxicity Common Sense Personal Safety The label is a legal document Foliar active/soil active Pre Emergence/Post Emergence Contact/Systemic Selective/Non Selective Selective application Glyphosate (Roundup) Biologically rational pesticide? Broad spectrum herbicide Post emergence/foliar active Weeds/trees/shrubs/bark Can be applied selectively Can be systemic Concentration varies by product Wind drift hazard/droplet size Phenoxy Herbicides (2,4D, Dicamba, Crossbow) Weed and Feed for Lawns Brush Killer Can be selective for broadleaf plants Post emergence/foliar active Can be systemic Volatilization hazard (air temperature) 8

9 Sugar Flow Carbohydrate starvation Cultivate then wait Sugar flows up away from roots Starve the roots Systemic effect of herbicides Actively growing weeds Sugar flows down to roots Sugar flow carries herbicide down Poison the roots Broccoli cover crop relay, plant and insect interactions Paul Buxman s peaches Creative use of weed shifts 9