Maintenance and care
Controlling weeds around your shelterbelt
Weeds are any plant that is considered to be competing with a shelterbelt for resources. Controlling weeds is important to limit competition and should be done throughout the shelterbelt’s lifetime, including before planting the shelterbelt.
Controlling weeds is important to limit competition and subsequent nutrient deficiencies that shelterbelts may face. Weed control should be done throughout the shelterbelt’s lifetime – from prior to planting, during the seedling stage, and through to maturity. Weed control is especially important before planting and during the first 3 years after planting, since this is when the plants are youngest and most vulnerable. Once larger, they have the possibility of shading out some of the close-by weeds themselves.
Weed control overall increases the health and longevity of shelterbelts.
Weed control begins before planting, when it is easiest to control the weeds.
- First, the site must be initially prepared. This is important because perennial weeds and grasses are much harder to control after the shelterbelt is planted. Hence, it is easier beforehand because it allows one to use a wider range of management practices with no endangerment to the shelterbelt.
- Glyphosate, a broad-spectrum herbicide, can be applied at the planting site one to two weeks before tillage in order to kill the weed root system.
- The planting site should be cleared of sod clumps and large stones as well.
Types of weed management
There are both mechanical and chemical types of weed management. A popular type of mechanical weed management is tillage. A popular type of chemical weed management is herbicide application.
- Mechanical weed management
- Mechanical cultivation, or tillage, is one of the most popular types of mechanical weed management.
- There is special equipment available for tilling within a shelterbelt row. Such equipment attaches to the side of a tractor and will either mow the weeds or fully till the soil. Advanced technological equipment can have sensors that specify when to go around a planted tree; otherwise this can be done manually. If tilling with planted trees or shrubs present, it should be done no more than 2 inches deep to avoid damaging any shelterbelt roots.
- Please see “HFIT” for more details on tillage.
- Chemical weed management
- Herbicide application is a popular type of chemical weed management.
- Please see “HFIT” for more details on herbicide application.
Controlling weeds between shelterbelt rows
In order to mitigate weed competition between shelterbelt rows, non-competitive turfgrass can be planted, the soil can be tilled, and/or mulch can be laid. Plastic and organic mulches are two popular mulch options.
Planting and maintaining (e.g. watering and mowing) a noncompetitive turfgrass (e.g. sheep fescue) in between the tree rows can mitigate weed competition.
Weeds between tree rows can also be tilled, which although is sometimes difficult to accomplish in such confined areas without harming the shelterbelt. Between-row tillage equipment includes disc harrows, cultivators and rototillers.
Controlling weeds between shelterbelt rows: Mulch
Mulch is an effective alternative to both chemical and mechanical weed cultivation and is more of a one-time expense. Controlling weeds by using mulches has been thought of as perhaps the most environmentally safe way to control weeds. Mulches can be organic such as wood chips, straw or hay, or can be inorganic such as plastic or woven fabrics.
Plastic mulch is an option to mitigate between-row weeds. Plants grow through small holes in a plastic sheet equipped on the ground surface. The plastic acts as a barrier to suppress weeds while also retaining water. The plastic suppresses the weeds by preventing necessary sunlight from reaching the ground.
- In addition to weed control, plastic mulch retains water for the shelterbelt by greatly reducing surface evaporation and stimulates both above- and below-ground shelterbelt growth by retaining soil warmth.
- Plastic mulch also works nicely with drip irrigation. See “HFIT” for more details on drip irrigation.
- Plastic mulch can be applied with the help of tractor-mounted or truck-mounted applicators.
- Choose plastic mulch resistant to UV light to prevent breakdown.
- Plastic mulch is susceptible to holes and damage from environmental disturbance such as wildlife and weather, so it must be periodically monitored.
- The colour of plastic mulch, due to its reflectance properties, can influence soil temperatures and thereby affect root growth.
- Woven black fabric mulches are a simple alternative as they not only control weeds, but also allow water to enter into the soil area.
Organic mulch consists of large organic materials such as wood chips to control weeds and conserve soil moisture in generally the same ways as plastic mulch.
- No special equipment is required to place organic mulch; simply apply the mulch to the ground surface area (although this application is labrous and large quantities of organic mulch may be hard to obtain).
- A 10 cm layer of organic mulch is required in order to adequately control weeds. It is important to note, if sawdust and/or other organic materials are applied greater than 10 cm deep, soil aeration can be compromised, which should be avoided.
- Organic mulches are positive in that they insulate the soil and limit temperature fluctuations, allowing for consistent growth of the shelterbelt.
- Mulching with grass or crop residue will have to be replenished more often than wood or bark chip residue, which the latter can last up to 5 years. Also, mulching with larger wood pieces reduces rodent populations and subsequent impacts on the shelterbelt.
Weed control and the nearby microclimate
In areas where there is complete weed control, the microclimate and microenvironment near a new shelterbelt is normally warmer and drier than the area surrounding it. Diversity of plant species in this area is diminished as well. Therefore, with less weed control there is more biodiversity in the area (more species, more habitats, etc.). Both weed control and biodiveristy is important, so this is something to think about while planning and maintaining your shelterbelt.
Pruning trees and shrubs
Tree pruning is the act of trimming or cutting away certain branches or stems of a tree to help the tree thrive and increase productivity, fruitfulness and growth. The three main reasons to prune a shelterbelt are to remove branches for disease control, hazard prevention, and/or aesthetic purposes. Pruning can help strengthen the plant and promote rapid growth, and can be done during multiple times of the year.
How pruning affects plant growth
When you prune a tree, you remove top growth but not root growth. Less top growth subsequently requires less water and nutrients. This greater amount of roots supplying nutrients to a reduced amount of top growth results in strong, rapidly growing, above-ground tree parts.
- Note that (often unwanted) suckers/shoots near the tree or shrub can rapidly develop as a consequence of this strong growth.
- Shoots often develop from the site of the pruning cut and grow in the same direction that the past branch had been.
- However, pruning should not be avoided because of the chance of shoots developing, since there are many other benefits to pruning.
There are three main reasons for pruning shelterbelts:
- Dead, diseased or broken branches are removed for safety purposes and disease control.
- Potentially hazardous branches that grow into areas interfering with power lines, machinery operations, or have the potential to damage properties, are removed.
- Suckers and wide-spread, interfering branches can be removed for appearance purposes.
- However, useful branches should not be removed if they are only simply an eyesore. Removing lower branches especially should only be done if there is a need to alter the windbreak provided by the shelterbelt.
- Other reasons for pruning:
- At planting time
- After transplanting a tree, some of the tops can be pruned in order to equal out the loss of roots. This helps train the tree to develop sufficient mass at a sustainable level. The amount of pruning for this purpose should not be more than one-third of the plant’s total top growth.
- For training purposes
- Pruning can be done to help the tree develop a strong framework for continual future growth.
- To develop a tree to withstand strong winds, a tree can be pruned to a few strong, widely-spaced limbs, so all nutrients absorbed can be forwarded to these few limbs, in order for them to grow to their full potential.
- To develop a shade tree, lower limbs can be pruned off to a height 2.5 m above the ground surface. Ideally this pruning is done over a long period of time so the tree remains strong and capable of adapting to limb removal without developing disease or other ailments. In addition, an encouraged option is to prune such lower limbs first to stubs, since these stubs act to draw up water and minerals, and can grow leafy shoots which further photosynthesize and make food, all aiding in creating an even stronger trunk. These stubs will eventually be removed as well.
- Pruning can be done to eliminate weakened branches that are in spots of competition with other branches
- Pruning can be done to benefit the undergrowth below the tree. For example, to revitalize the lawn below the shelterbelt.
- At planting time
Pruning can be done during multiple times of the year.
- Advantages to pruning in the later winter or early spring:
- There is less damage from infection between trees. But, pruning at this time can result in a fewer number of leaves being produced the following year.
- Deciduous trees and shrubs are recommended to be pruned when they are dormant, such as early spring, since at this time healing will be done rapidly and almost immediately. The subsequent growth can also be less negatively affected if pruning is done at this time.
- Advantages to pruning in the summer:
- When the trees are in full-leaf, it is exceptionally easy to locate dead or diseased tree limbs.
- As an exception to the dormant pruning rule, maple, birch and elm should be pruned in mid-summer so they do not lose excessive sap like they would during the other times of the year. Mid-summer would also allow them to have enough time to heal properly before the next winter.
- Pruning of dead branches can overall be done at any time since no living tissue will be affected.
How to prune a tree or shrub
Appraise the tree and the adjacent area in order to select the proper branches to cut, and to decide on a safe removal method. The 3-step cutting method is recommended in order to avoid damage to main limbs or trunks of trees when pruning. It is important to ensure the maintenance of the natural form of the tree, and to remove only what is necessary.
First, appraise the tree and the adjacent area in order to select the proper branches to cut, and to decide a method for removal that safely lets them fall to the ground. With this initial preparation, there is less chance of damage being done to you, the tree, or the area around the tree.
It is recommended to remove around 15 cm or more below any evidence of disease. This usually means to simply cut back to a living, healthy branch; either a lateral branch, meaning the main branch from which the diseased parts are growing from, or the trunk.
The 3-step cutting method is recommended in order to avoid damage to main limbs or trunks of trees when pruning.
- The first cut is made part-way through the diseased branch on the underside
- The second cut is made 2-3 in inches further out on the branch, top-down. The weight of the branch will cause it to break free of the main tree and fall, all without any excessive bark or tree damage.
- A third cut is then made reasonably flush with the main limb or trunk so as to remove the stub left behind from the fallen branch. This leaves a flush and minimal exposed surface that will allow the cut to heal properly over time.
- And of course, always take caution when pruning in order to avoid accidents that could cause harm to yourself or the tree or shrub.
When pruning, it is important to ensure the maintenance of the natural form of the tree. Major alterations should not be executed unless completely necessary.
When pruning, remove only what is necessary, in order to maintain shelterbelt density so the trees can fulfill their full potential in their purpose of reducing wind, for example. In any case, do not remove more than 25% of living tree parts in one season.
Pruning equipment includes, but is not limited to, handsaws, polesaws, bucksaws, chainsaws, secateurs and lopping shears. Be sure to care for and periodically disinfect your tools as sometimes they may contain harmful bacteria or chemicals from other trees.
There are specific saws designed for pruning that are compact and designed for large pruning jobs in small spaces. For example:
- Similar idea to a bow saw; a bucksaw is a hand-powered saw with a normally “H-” or “C”-shaped metal frame, and can be a one- or two-person saw.
- Can be used for cutting large limbs
- Chainsaws are not recommended since although they are fast and efficient, they often do not cut cleanly through the wood. This lengthens healing time.
- Also called “pruners”, secateurs are small, single-hand pruning clippers used for small branches.
- Scissor-action secateurs are often considered the best at making exceptionally clean cuts. Anvil-action type secateurs are also an option.
- Lopping shears
- Lopping shears are two-handed pruning shears with handles normally 1-3’ long and used for smaller branches. Some loppers can be bought with handles that have extensions up to 2 m long.
- Handle lengths differ, and some lengths can work better than others for certain pruning jobs.
- Scissor-action lopping shears are also recommended over anvil-action ones.
- Always ensure your pruning equipment and tools are in good condition in order to make sharp, clean cuts into branches. As well, when dealing with diseased parts, disinfect your tools between each cut. A 5% javex or an alcohol solution will work for disinfecting.
Pruning evergreens (coniferous trees)
Many evergreen trees have a classic pyramid shape which should be maintained whenever possible. Removal of entire branches should only be done when absolutely necessary. Overall, pruning of coniferous shelterbelts is regularly only done by trimming the tips of the branches.
Although the 3-step deciduous method can also be used for large evergreen pruning jobs, many evergreen trees have a classic pyramidal shape, and this shape ideally should be maintained since it is how these trees naturally thrive. Removal of entire branches should only be done when absolutely necessary, e.g, due to reasons such as disease.
After pruning an evergreen, other adjacent lateral branches can be trained upwards and towards the direction of the gap in order to replace the pruned limb and retain the pyramidal shape.
Overall, pruning of coniferous shelterbelts is regularly only done by trimming the tips of the branches. If this pruning pattern is done routinely, noticeable increases in shelterbelt density can be seen.
- Controlling weeds in your agroforestry planting. (2016). Government of Canada. https://www.agr.gc.ca/eng/agriculture-and-climate/agricultural-practices/agroforestry/growth-and-maintenance-of-trees/controlling-weeds-in-your-agroforestry-planting/?id=1346110876860.
- Esau, R. (2007). Weed control for Alberta shelterbelts. Alberta Agriculture and Food: Agri-facts. https://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex977/$file/277_645-1.pdf?OpenElement.
- Plastic mulch. (n.d.). Wikipedia: The Free Encyclopedia. https://en.wikipedia.org/wiki/Plastic_mulch#Weed_management.
- Pruning trees and shrubs. (2015). Government of Canada. https://www.agr.gc.ca/eng/agriculture-and-climate/agricultural-practices/agroforestry/growth-and-maintenance-of-trees/pruning-trees-and-shrubs/?id=1346179616865.