Weed Control in Community Gardens


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Dr. Chuck Marr
Kansas Community Gardens Conference, July 8-9, 2013

This presentation will focus on various types of common garden weeds and strategies
to control them. In addition, special considerations for weed control in community
gardens will be discussed. Some special attention will be provided for bindweed and
bermudagrass, two especially difficult weeds to deal within community gardens.

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Weed Control in Community Gardens

  1. 1. Dr. Chuck Marr Professor (Emeritus) of Horticulture Kansas State University
  2. 2. Weeds grow to fill fertile, open, well- watered spaces Something will grow – probably weeds Weeds are natural competitors • Abundant seed production • Seed dispersal • Spreading stems/roots • Withstand stress • Grow rapidly
  3. 3. Compete for • Fertilizer (which you pay for) • Water (which you pay for) • Sunlight • Space Weeds are natural competitors and most crops will lose (a few crops can hold their own) Weeds do cover bare spaces and add organic material to soils when incorporated
  4. 4. Many garden plots in a small area Paths and ‘between plot’ areas Season-long production
  5. 5. ‘People’ problems associated with weeds • Articulating guidelines about weed control • Weeds spreading from one plot to another • Dealing with weeds in a timely manner • Who gets to clean up areas where weeds get out of control Knowledge of weeds- know weeds from the crop
  6. 6.  Grasses • Dense aggressive roots • Compete for nutrients and water • Hard to hoe later (multiple stems) • Slow down late in the season  Broadleaf • Grow taller than crop • Compete for light and space • Tough stems later • Germinate readily after a rain • Grow rapidly when 4-6 inches tallSedges ‘Nutsedge’
  7. 7. Germinate in autumn and grow rapidly in early spring Dense, spreading growth (not tall) Die when temperatures get warm (June) Chickweed, Henbit, Pennycress are examples Late tillage will control many of these weeds
  8. 8. Broadleaf and grasses Germinate in May Grow rapidly in warm temperatures After they get 4-5 inches tall they become more difficult to control Crabgrass, foxtail, lambsquarter, pigweed purslane
  9. 9. Storage root system (will come back from roots) Get larger each season Mixture of old and newly germinated plants Dock and dandelion are examples Controlling them in the 1st season is important
  10. 10. Can develop in fences or between plots Woody stem (can’t hoe) Root system is extensive Must control early Chinese elm, maple, hackberry, oak (acorns) are examples
  11. 11. Field Bindweed Bermudagrass These 2 special perennial weeds require some special consideration for ways of dealing with them and strategies for keeping them from re-occurring. More about these later…….
  12. 12. Cultural • Crop canopy, mulches, soil solarization Mechanical • Hoe, mini-tiller Chemical • Selective, non-selective Most gardeners will rely on multiple strategies to deal with weed problems in a wide range of crops through the season
  13. 13. Select in-row and between row spacing for maximum cover Keep weeds out until canopy forms Some crops are better than others for making a canopy Sweetpotatoes, potatoes, beans, tomatoes, spinach all will make dense canopy Cultural Methods
  14. 14. Plan spacing to provide crop development and shade everything else. Good example Bad example
  15. 15. Mulch shades soil surface so weeds cannot germinate Organic mulches- straw, prairie hay, compost, etc Fabric mulches- black plastic, landscape fabric
  16. 16. Make sure grass clipping are dried before use ( OR apply a thin layer several times) Weed seeds can be present in straw or hay Herbicide (applied in the spring) can be present in grass clippings or hay Testing for herbicide residues is EXPENSIVE and you must know the general category of chemical that you suspect might be involved.
  17. 17. Weed seeds present in mulch created a crop of weeds (in this case wheat) Interface between mulched and non-mulched area can be a problem area to prevent weeds from developing.
  18. 18. Use sunlight/heat to kill weed seeds •Till and smooth the soil (no clods or sticks) •Wet the area •Cover with clear plastic •Tuck in the edges •Allow to remain for 1 month •July and August best
  19. 19. Shallow scraping on small weeds ‘Dust’ mulch will be created Make sure hoe is sharp A ‘standard’ or ‘all-purpose hoe is not always the best for weed control Mechanical Methods
  20. 20. Onion Hoe Warren Hoe Scuffle Hoe Hula Hoe (Scuffle)
  21. 21. ProHoe.com Munden, KS A wide range of hoes to choose from. Excellent steel blade and high quality ash handle Quantity Discount Pool order for shipping charges
  22. 22. A ‘mini tiller’ can go between garden rows. Most tillers are 2-cycle engines- requiring oil-gas mixtures to operate Cultivate- going forward Till- pulling backward Hard to start- high maintenance
  23. 23. Non-selective (kills any green vegetation) Selective (kills some but not others) Pre-emergent (before weeds grow) Post-emergent (after weeds are present) There is nothing that controls all weeds and is safe to use on any or all vegetables or flowers. Choices must be specific for the type of weed and the type of crop.
  24. 24. Roundup (glyphosate) Kills any green vegetation Moves throughout the plant to kill roots Deactivated by soil Only ‘spray particles’ will drift Uses Spray area before planting Spot treat individual weeds Dip cloth glove and touch plant Fall applications for perennials Avoid using pre-mixed spray bottles. Get concentrate and mix your own in a sprayer or spray bottle. Can keep for a number of years.
  25. 25. Poast (sethoxydim) HiYield Grass Killer, Grass Getter, etc. Kills grass in broadleaf plants Grass must be actively growing Best when grass is 2-4 inches tall Grass stops growing immediately but it takes 10 days -2 weeks to see the grass completely die Will not harm broadleaf plants (not Corn=grass) Great for grass in perennial flower beds, strawberry beds etc.
  26. 26. Preen or HiYield Herbicide Granules (treflan) Sprinkle granules on tilled soil Don’t hoe or cultivate after application Lasts 5-6 weeks May let a few weeds develop Must read label for crops it can be used on Kills only germinating weed seeds- not existing weeds. Forms a chemical barrier when watered in that prevents weed germination in that zone , , ,
  27. 27. Tilled and seeded on June 3. Treflan granules applied immediately after planting and watered. Photo on June 30 Only pulled a few lambsquarter and pigweed that were missed with tilling.
  28. 28. 1 lb/1280 sq ft. 20 ft 15 ft 20 X 15= 300 sq ft 300/1280= .234 lb Measure out ¼ lb, gradually scatter it over the entire area
  29. 29. All chemicals must be applied by the ‘purchaser’ -poured from the original container with the label/MSDS information available OK Gardener applies to his/her own garden and some others Gardener applies to common areas Gardener allows others to use a sprayer he/she has mixed up Several gardeners ‘split the cost’ of a bottle they will ‘share’ NOT OK Gardener pours from his/her bottle into another bottle Chemical in garden shed for ‘common use’ Gardener charges someone else for spraying their garden
  30. 30. ‘Spade’ shaped leaves with white flowers in a vining plant Propagates by seed and underground roots If cultivated, chopped pieces each re-root. New plants develop from seed ‘Field Bindweed’ – not necessarily other plants that may twine or sprawl.
  31. 31. Almost impossible to control it during the growing season. Control Measures: 1. Wait until early September and allow foliage to grow to develop some leaf surface. 2. Apply Roundup to foliage, wait 2 weeks and look for any newly emerging plants. Treat again 3. Don’t till or disturb until mid- October to early November. 4. Watch for spread from nearby areas
  32. 32. Alternative Control Measure: works best in mid-summer 1. Till and smooth an area of the garden 2. Apply clear plastic 3. Remove plastic and re-till monthly 4. Allow to remain at least 4 months 5. Till in late Oct –early November
  33. 33. Bindweed and Bermudagrass can be spread by bits and pieces clinging onto garden tools, mowers, or tillers. A slight piece is all that is needed to start the weed in a new location.
  34. 34. A warm-season grass that doesn’t start growing until mid- late May Spreads by above ground runners and below ground ‘rhizomes’ and small seeds If you till or hoe, rhizomes re- root to form new plants. Slows down and stops growing in early October.
  35. 35. Control measures work best in hot, dry summer weather on grass that is actively growing. 1. Treat actively growing grass with Roundup (non-selective) or Poast (selective) 2. Allow to remain uncultivated for 1 month and re-treat if signs of green reappear 3. Till in late October to early November Alternative Control: 1. Cover area with clear plastic and allow to remain 4 months (do not uncover) 2. Till in late October to early November
  36. 36. Be careful about leaving any ‘dead’ Bermudagrass anywhere in the garden area. It can withstand excessive stress- looking ‘dead’. But a little water and off it grows.
  37. 37. www.ipm.ucdavis.edu/PMG/weeds_intro.html http://weeds.cropsci.illinois.edu/weedid.htm Some good references for weed identification. Local K-State Research & Extension office for personal identification
  38. 38. Copy of this presentation Copy of handout Questions? cmarr@ksu.edu