JOURNAL OF REFORM/ WINTER 1994 • VOL.14, NO. 4

● ALTERNATIVES LANDSCAPE

To a child a dandelion may be a cheery flower, but to his parents a dandelion may be a bane in the backyard. What makes a wildflower a weed is the damage it causes to more desirable species. This can be perceived aesthetic damage or damage due to increased competition for water and nu- trients. Many gardeners use to get rid of these weeds. However, it is pos- sible to manage weed problems without causing more damage to the environment by using herbicides.1 Weed Identification Before embarking on a weed control pro- gram, it is important to accurately identify the weeds. Weeds can be classified into two types: annual and perennial. Annuals grow, produce seeds, and die in one year. Perennials live for several years, each year saving energy in their roots to survive the winter. will grow best in each zone. Choose Cultivation: Before you plant, the area Make a survey of the area to be weeded that are resistant to diseases and that are ad- should be cleared of weeds to prevent future and identify the various weeds that are present. justed to your local climate, since healthy vig- weed problems. One method of doing this is Consult your local library for weed identifica- orous plants will not be susceptible to weed by cultivating manually or with a rototiller. tion books for your geographic area. Or, take damage.1,2,4 To control annual weeds, cultivation should the weed to your county extension service for Plants that have similar light and water be followed by irrigation. After the weed seed- identification. needs should be planted together.3 Consider lings germinate (1-3 weeks later), cultivate and Find out whether the weeds common in installing low volume, subsurface or drip irri- irrigate again. Repeat these steps two or more your are indicators of a condition gation systems that make water available only times, each time cultivating at a shallower that needs correcting. Use information about to the root zones of desired plants.1,3 depth. the particular weed to determine how aggres- Raised flower and beds with per- While most successful with annual weeds, sively the weed grows and spreads, how visible manent paths between them solve the prob- frequent cultivation may also control peren- it is, and how much damage it is likely to lem of conventional garden or flower patches nial weeds under dry conditions. Damage cause. Decide which weeds to tolerate and where the areas not occupied by plants are caused by repeated cultivation (every 3 weeks) which ones to control.3 colonized by weeds. For weed control on paths requires perennials to use their stored energy or gravelled areas, put three layers of roofing reserves and eventually die. Moist soil condi- Planning Ahead paper on the soil, then overlay the paper with tions will allow perennial weeds to spread. The easiest way to solve weed problems is gravel. Use the same technique to create strips Therefore cultivation should not be followed to prevent them by planning ahead when you of weed-free areas under fences and next to by irrigation when targeting perennials.1 plant your yard. Divide your yard into zones walls.1,3 Soil solarization: This is an effective means based on the amount of light they get. Find It also helps to separate shrub areas from of ridding areas of annuals and some peren- out what kind of soil you have and how well turf or groundcovers with paths or headers. nial weeds for six to twelve months. Solariza- it drains. Then determine which kinds of plants Headers are wood, metal, or concrete dividers tion may also control soil-borne disease and that are 12 inches high (8 inches under the nematodes. ground and 4 inches above the ground).1,3 To use solarization effectively, any vegeta- Carrie Swadener is NCAP’s information services tion should be mowed to less than one half Weed Control Before Planting coordinator. inch. The soil should be tilled for planting so

NORTHWEST COALITION FOR ALTERNATIVES TO /NCAP 22 P.O. BOX 1393, EUGENE, OREGON 97440 / (541)344-5044 JOURNAL OF PESTICIDE REFORM/ WINTER 1994 • VOL.14, NO. 4 that disturbance after solarization is unneces- Any mulch will require some maintenance from potential damage from weed trimmers sary. Water the area, then cover it with to remain effective. Remove any weeds as soon by putting shields around them.1 2 millimeter thick clear plastic. The as they sprout to prevent future weed coloni- Flaming: Flamers emit a flame designed ground should be as level as possible. zation and damage to any underlying land- to kill weeds by burning their basal stems - Seal the edges of the tarp with soil and scape fabrics. Keep all mulches several inches the part of the stem near the soil surface. repair any holes in the plastic. The tarp away from trunks, or apply only a thin layer. The flame should be touched only at the should remain over the area for up to Any area to be mulched must be first cleared basal stem very briefly. Damage may not six weeks during the hottest time of the of established weeds and properly prepared for be noticeable right away, but the weed year. Leave the tarp for longer periods future planting.1 should die after several days. Perennial in cloudy, windy, or coastal areas. Plant weeds, grasses and older weeds may need soon after removal and avoid soil dis- Weed Control in Planted Areas to be retreated after one week. Be careful turbance deeper than three inches.1 Prevention: Before using organic mulches, not to burn nearby shrubs or trees, and do Mulches: The use of mulches, a layer of compost them properly to prevent introduc- not use flamers in dry areas or around material that prevents sunlight from reaching ing weed seeds or parts that may sprout. When mulches that may burn or melt. Flaming the soil, is a very effective control of annual buying soil or mulch, make sure they have may be used in areas with wood mulches if weeds. There are both organic mulches, like been sterilized by kiln drying or steam. Clean the soil surface is touched very briefly with sawdust, clippings, straw or bark, and mowers and other equipment of seeds and the flame and caution is exercised. Water inorganic mulches, such as crushed rock, plas- other plant parts before using them. Filter seeds or a fire extinguisher should be kept nearby tic or specially designed fabrics. Mulches also and weed parts from surface water before us- when flame weeding.1 retain water, and reduce soil erosion and com- ing it for irrigation.1 Remove all weeds (par- paction. ticularly annual weeds) before they seed.1,3 Conclusion Organic mulches benefit the soil by gradu- Hand weeding: Hand-weeding is a very Nonchemical weed control is a combi- ally decomposing and adding nutrients to the effective method of weed control in established nation of methods. Identifying problem soil, and may aid water penetration into the landscapes and . It is easiest when weeds weeds and tolerating more benign weeds is soil. However, they may harbor potentially are small, and when the soil is loose and moist. the first step. Determining the conditions harmful pests. Organic mulches should be ap- Perennial weeds are best controlled if attacked encouraging the presence of weeds and cor- plied at least three or four inches deep to pre- when their food resources are low, i.e. just recting them is the next step. Techniques vent light penetration. More mulch should be after leafing out or just after flowering. At these promoting healthy and hardy desired plants added as the previous mulch decomposes. Con- times, the chances of resprouting are reduced. that outcompete undesirable weeds and sider fertilizing with an organic source of ni- Although perennials may resprout for several constructing barriers to prevent weed inva- trogen, as decomposing organic mulch may seasons, the diligent gardener should prevail if sion are invaluable in any weed control pro- temporarily deprive plants of available nitro- the weeds are destroyed repeatedly at these gram. Methods of removing weeds effec- gen.1 susceptible times.1 There are specialized weed tively with minimal environmental damage Inorganic mulches are sometimes less at- pulling tools such as weed poppers that pull are also important. All these methods work tractive than organic mulches, but may be weeds and their roots, but do not substantially together to produce a landscape that is aes- equally effective. They do not add to soil qual- disturb the soil.1 thetically pleasing as well as one that en- ity. However, inorganic mulches require less Hoeing: For the most effective hoeing, cut hances the natural environment. maintenance and do not need to be replen- grass weeds slightly below the surface, and other References ished. Often a top layer of bark is applied to weeds at the soil surface, instead of chopping 1. Dreistadt, S.H., Clark, J.K. and M.L. Flint. 1994. both improve the landscape’s appearance and them. Keep the hoe blade sharp to cut weeds Pests of landscape trees and shrubs: An integrated protect the mulch from damage by and without disturbing too much of the soil sur- management guide. University of California Division of and Natural Resources Pub- ultraviolet light. face. Hoe when the soil is dry, and allow the lication 3359. Some plastic mulches are waterproof, so cut weeds to dry out before irrigating the area.1 2. Thurston County Local Hazardous Waste Program. Undated. Understanding weeds: A guide to weed sprinklers cannot be used for irrigation. These Specialized tools can be useful. For example, control for the earth-friendly gardener. Common mulches may also promote fungal infections. the Action Hoe is a hoe that is designed to cut Sense series. 3. Olkowski, W., S. Daar and H. Olkowski. 1991. Com- Landscape fabrics and weed barriers are syn- weeds at the soil surface rather than chop- mon-sense pest control: Least toxic solutions for thetic polypropylene materials that allow air ping.5 your home, garden, pets and community. Newtown, CT: The Taunton Press. and water penetration to roots and are more Mowing: Mowers, sickles, or weed trim- 4. Thurston County Local Hazardous Waste Program. durable than plastic. Some are designed to mers are effective in cutting down grasses and Undated. Plan Before You Plant: A guide to land- scape planning for the earth-friendly gardener. break down over time. This is desirable when tall weeds before they bloom and produce Common Sense Gardening series. temporarily mulching new plantings that will seeds. This allows weeds to be tolerated in 5. Johnson, D. 1991. Weed management for the lawn and garden. Washington Toxics Coalition Alterna- eventually grow thickly enough to shade out some areas, but prevents them from spread- tives Fact Sheet. Seattle, WA. weeds.1 ing to other areas. Protect nearby tree trunks

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