Tips on Use of Herbicides in Home Gardens
By: Khursheed Mama
Colorado State University Extension Master Gardener in Larimer County
Spring is an ideal time to plan for the growing season ahead. While it is natural to focus on the plant material, this is also a time of year to consider whether the garden may benefit from other forms of rejuvenation including materials to enhance the soil and minimize weeds. Soil amendments include any material that is mixed into the soil and include materials such as compost or manure as well as fertilizers http://www.ext.colostate.edu/pubs/garden/07235.html [1].
The purpose of these products is to add organic material and nutrients to enhance growth of garden plants which in turn naturally help limit weed populations. Good cultural practices, such as providing irrigation only to planted areas, selecting appropriate plants, using mulch, biological controls and mechanical methods are also recommended. However, there are times when the application of herbicides may be necessary and understanding options can be helpful in ridding the garden of ‘weedy’ plants while minimizing the negative effects on desirable plant material and the environment (http://www.ext.colostate.edu/mg/Gardennotes/351.pdf [2]).
Two broad groupings of herbicides include “pre” and “postemergent” and refer to how they are most effective in the plant’s life cycle. Preemergent herbicides do not prevent germination but work on the young, growing seedling plants and when used appropriately do not kill established plant material. They will not kill already present weeds. Most are best placed under mulch or watered into the soil. Postemergent herbicides work on growing plant material and are typically sprayed or wiped directly onto the plant. These herbicides may be specific to certain types of plants (i.e., fluazifop for grasses) or more generally active / non-specific (i.e., glyphosate). In certain circumstances, herbicides may also be incorporated into the soil prior to planting, which is recommended for vegetable gardens. It is critical to read the label, understand the type of application and follow the directions. The label is the law.
When making a selection gardeners should be aware that both organic (i.e., corn gluten meal) and synthetic (i.e., trifluralin) herbicides are available. Herbicides function in different ways; some rapidly kill (burn) living plant material and are sufficient for control of annual weeds, whereas others are systemically translocated and more broadly effective, but usually take longer to work. To limit weed propagation, both the plant and seeds need to be controlled, making timing of application of herbicides critical. Since weeds have different growing seasons similar to garden plants, more than one application or type of application may be necessary. This is especially true in the case of perennial weeds, like bindweed.
For more information on herbicides for specific situations, refer to http://www.ext.colostate.edu/ptlk/2104.html and http://www.ext.colostate.edu/mg/Gardennotes/552.pdf [3].
Gardening Q&A
By: Khursheed Mama
Colorado State University Extension Master Gardener in Larimer County
Why isn’t my forsythia flowering?
If you are new to Colorado you may have wondered why your early blooming shrubs such as forsythia and lilac haven’t bloomed like those of your neighbors. If the shrubs are otherwise healthy, this is usually easily corrected with appropriate timing of pruning. For early spring-blooming shrubs, flower buds are set on year-old wood. The plant set the buds for this year’s spring blooms through the summer and fall of the preceding year. If one pruned these shrubs after the buds were set (late summer), the flower buds are lost. With appropriate pruning early this year, next year’s flowers will not be affected. If shrubs are older and don’t appear healthy, they may benefit from ‘rejuvenation’ pruning. This may be done at any time during the year, but timing will, as stated above, further influence flower set. For more information on different pruning methods and timing, please refer to http://www.ext.colostate.edu/mg/gardennotes/616.html [4]
What should I do when my bulbs are done flowering?
With the warmer weather we experienced in March, spring bulbs are in full bloom all around town. Soon we will be left with wilting foliage and no flowers. While it is tempting to remove the same due to its unsightly nature, try and resist the urge. The foliage provides nutrients for the bulb and helps its long term viability. A good alternate management strategy is to plant early spring blooming perennials next to bulbs so that they draws attention—and the withering foliage can “hide” under the other perennials. If you want to move and replant bulbs, doing this after the flowers are spent and before foliage dies back allows you to locate the bulbs and gives them an entire season to become reestablished in an alternate location. Transplanting and maintaining bulbs http://www.ext.colostate.edu/ptlk/1010.html [5]
When should I prune my rose bush?
Mid-to-late April is a good time to prune rose bushes just as the stems are starting to green up and buds begin to swell. For starters, dead or woody stems should be cut back, as should any suckers (stems that rise vertically). The plant may then be cut back and shaped as desired following general pruning principles. Make cuts approximately a quarter inch above a swollen outwardly facing bud or leaf axle at approximately a 45 degree angle. You will need sharp, clean pruning tools. Gardening gloves and protective clothing are suggested. For general information about pruning and specific information on pruning different types of roses please see http://www.ext.colostate.edu/mg/gardennotes/616.html [4] and http://www.ext.colostate.edu/ptlk/1763.html [6]
The author has received training through Colorado State University Extension’s Master Gardener program and is a Master Gardener volunteer for Larimer County.
Larimer County is a county-based outreach of Colorado State University Extension providing information you can trust to deal with current issues in agriculture, horticulture, nutrition and food safety, 4-H, small acreage, money management and parenting. For more information about CSU Extension in Larimer County, call (970) 498-6000 or visit www.larimer.org/ext [7]
Looking for additional gardening information? Check out the CSU Extension Horticulture Agent blog at www.csuhort.blogspot.com [8] for timely updates about gardening around the state.
Visit PlantTalk Colorado ™ for fast answers to your gardening questions! www.planttalk.org [9] PlantTalk is a cooperation between Colorado State University Extension, GreenCo and Denver Botanic Gardens.