Principles of Water Wise Landscaping
A water-wise landscape is one that is functional, attractive, and easily maintained in its natural surroundings. A water-wise landscape also helps to conserve water. If you live in Utah, you have undoubtedly heard that Utah is one of the driest states in the nation, second only to Nevada. This fact, along with our relatively high level of water consumption and our population growth, has brought water conservation to the forefront of those natural resource issues currently facing the state.
In Utah, approximately 65% of our annual culinary water consumption is applied to landscapes. Our irrigated landscapes provide us with many benefits that include beautiful surroundings, natural cooling, and the cleansing of our environment. However, Utah landscapes are often over-irrigated and a great deal of water conservation may be achieved by keeping a few water-wise landscaping principles in mind as we design, install, and manage our landscapes.
Water-wise Landscaping Principle # 1: Planning and Design
A landscape design should meet the needs of the people who will use and maintain the area while incorporating the site’s existing environmental conditions into the design. Water is a limiting resource in Utah, so designing the landscape to efficiently use water is important.
A landscape design should meet the needs of the people who will use and maintain the area while incorporating the site’s existing environmental conditions into the design. Water is a limiting resource in Utah, so designing the landscape to efficiently use water is important. Conserving water in the landscape can be accomplished by selecting low water use plants, designing and scheduling irrigation systems efficiently, grouping plants according to their water requirements, and using hardscaping materials (patios, stone paths, decks, etc.) appropriately to reduce the area requiring irrigation.
Developing a Plot Plan
Develop a plot plan of the area to be landscaped. This is simply a map of the building and lawn along with the location of existing structures, trees and shrubs, property lines, driveways, gardens, utility lines, contours of the land, or other possible limitations to the design. Use graph paper to prepare a scale map of the property and let each square represent a certain distance.
Conducting a Site Analysis
Visit the site to look for the environmental assets and constraints that will influence the design. Take notes on such factors as seasonal effects of sun and shade, soil conditions, slopes, direction of winds, and views from various points on the site.
Planning the Design
Based on the environmental considerations found in the site analysis, decide where plants should be placed for optimum aesthetic value, screening of undesirable views, shade or windbreaks, and separation of areas of the yard. Consider the use of hardscaping materials such as patios, walks, screens, and lighting. These materials can enhance the design while reducing the amount of area that needs to be irrigated and maintained.
Deciduous trees should be placed on the south, east and west sides of the building to take advantage of the potential benefits of summer shade and winter sun to heat or cool the building. Evergreens are good insulators but limit sunlight, so try to plant them on the north side of the building. In order to protect a home from cold and snow, use trees and shrubs as insulators or windbreaks along the building.
When choosing plants, identify their water requirements and group those with similar irrigation requirements in the same area or irrigation zone. This will help to more accurately meet plant water needs while conserving water. Zones can be separated into zone 0 (no irrigation), zone 1 (irrigate monthly), zone 2 (irrigate twice per month), zone 3 (irrigate weekly) and zone 4 (irrigate twice per week). Plants adapted to the dry conditions of Utah will survive with little or no water (zone 0). It is important to know the water requirements of the plants at the site to most efficiently meet these needs without wasting water. The watering zone designs will depend on the amount of water you wish to use for the landscape, how much money you can spend on landscape water, and what you wish to achieve aesthetically and environmentally.
Principles of Design
There are several basic principles of design to consider when planning the landscape. Along with the ones listed below, remember the importance of simplicity and harmony in designing.
Balance—Balance can be symmetrical or asymmetrical. Symmetrical is a more formal style of design with materials on one side mirrored on the other. Asymmetrical balance can be achieved by using different elements to create a more informal equilibrium. This may require using a group of smaller shrubs to counterbalance a large tree on the opposite side.
Unity—Group plants to achieve a unifying effect in the landscape (usually in groups of 3, 5, or 7). Plants can be grouped according to color, texture, or form. However, some variety in color, plant material, hardscaping textures, etc., adds interest to the landscape.
Rhythm—Repetition of elements (colors, textures, plant form) in the landscape provides a feeling of continuity and helps lead the eye through the landscape.
Accent—Accent is also referred to as dominance. Balance and rhythm can help lead the eye through the design to the focal point (accent). Examples of focal points may be a building, large tree or bed of bright flowers in front of a row of green shrubs.
Water-wise Landscaping Principle # 2: Soil Preparation
The most basic component of your landscape is the soil and many landscape problems can be avoided if an adequate amount of time is spent on properly preparing the soil before the landscape is installed. The types of plants that you are growing will have a bearing on the characteristics you require from a soil, but there are some general guidelines to follow.
Most plants do well under a range of soil conditions, however many plants have an optimum pH range, salt tolerance level, and soil moisture requirement. In choosing plants for Utah, remember that most soils have an alkaline (high) pH and some have moderate to high salt levels.
The most basic component of your landscape is the soil and many landscape problems can be avoided if an adequate amount of time is spent on properly preparing the soil before the landscape is installed. The types of plants that you are growing will have a bearing on the characteristics you require from a soil, but there are some general guidelines to follow. Using plant species that are adapted to the soil will help minimize maintenance and water required. Two major concerns are adequate depth of topsoil and the quality of topsoil. A depth of 8-12" is ideal and will solve many problems in the future.
Plant growth and ease of maintenance are improved immensely by high quality soils. Landscape soil quality can be improved by keeping it clean during construction, tillage to reduce compaction, and amending with fertilizers and organic matter. To amend soils correctly requires an understanding of the following characteristics.
- Soil texture: This refers to the percentages of sand, silt, and clay in a soil. Sandy soils drain quickly and retain little water or nutrients. Clay soils consist of much smaller particles and have less drainage, but better nutrient retention than sandy soils. Soils with appropriate balances of sand, silt, and clay are described as loamy. Loam soils, or close relatives such as clay loams or silt loams, are the best soils for plant growth.
- Soil structure: Structure refers to the degree to which small soil particles clump together, forming both large and small pores throughout the soil. This clumping aids water and air movement in the soil because water and air can move freely through the large pores. At the same time, the smaller pores within the aggregates hold water for plant use.
- Soil organic matter: Organic matter is beneficial in soil because it decomposes to provide plant nutrients. Organic matter also improves water infiltration, drainage and retention in the soil, largely due to its ability to improve soil structure. Manure, compost, leaves, and grass clippings are sources of soil organic matter.
- Nutrient status: The nutrient status of the soil refers to the amount of nutrients such a nitrogen, phosphorus, and potassium in the soil. These nutrients and several others are essential for proper plant growth. If nutrients are limited then plant growth suffers because of deficiencies. On the other hand, excessive levels of nutrients or other compounds, such as sodium chloride, can result in salty soils. Saline soils are difficult for plants to grow in because high levels of salts make it hard for plant roots to absorb water.
- Soil pH: This refers to the acidity or alkalinity of the soil. It is important because the soil pH affects the availability of mineral nutrients to plants. For example, Utah soils have high levels of iron, an essential mineral. However, due to the high pH of these soils, the iron present is not readily available for plant growth.
The most effective way to determine a soil's characteristics is to have a soil test done. Soil testing is done by commercial laboratories, or through agencies such as the Soil Testing Laboratory at Utah State University . Instructions and sampling kits for soil tests are available at county Cooperative Extension offices.
Plant selection is a fun part of the design process for most people and selecting the right plant for the right place is essential for creating a water-efficient landscape. Visit local water-wise demonstration gardens to get ideas for plant combinations and mature sizes. The following water-wise plant lists were created for arid Utah landscapes.
- Fit and Function: Choose plants based on height, width, shape, color, and form that will best help accomplish the design goals. Plants can be used to conserve energy or water, block undesirable views or noise (dense plant material), control erosion on steep slopes (lower growing groundcovers) and attract birds, butterflies and bees. There are many resources for water-wise plant lists and tree selection that are searchable by desired characteristics and water use.
- Choose Adapted Plants: Use plant species that are adapted to the landscape environment—the soil, water, temperature, light, and pest conditions—to help minimize maintenance and water requirements. This does not necessarily mean that water-wise landscapes are composed entirely of native plants. In fact, some native plants, such as Aspen, do not generally do well at the altitudes and water levels in most gardens as they are adapted to high elevations and wet-meadow situations. There are many plants from other dry regions around the world that are well-adapted to suit the low-water requirements of our region.
- Hydrozones: Grouping plants according to their water needs allows for more efficient irrigation as plants are less likely to be over or under-watered. Also, remember that smaller plants tend to have lower water requirements than larger plants.
- Seasonal Interest: Think about the timing of the foliage, bloom and seed head displays of the planting material to ensure interest year round. Try to Incorporate spring, summer and fall interest in each planting group so that no place in the landscape looks bare.
- Hardiness Zone: Use plants that will survive in our climate. Plant hardiness zones in Utah range from 4-9. The hardiness zones were established by the USDA and are based on the minimum, annual survival temperatures for plants. Plants for hardiness Zone 4 can survive -20 to -30 °F, Zone 5 can survive -10 to -20 °F, Zone 6 can survive 0 to -10 °F and Zone 7 can survive 0 to 10 °F. However, micro-environments created by the plant’s surroundings can also influence its hardiness for the region. Contact your local Utah State University County Extension Agent or go to the USDA Plant Hardiness Website to learn the hardiness zone of your area.
Water-Wise Landscaping Principle # 4: Practical Turf Areas
Lawns have many benefits including cooling effects, erosion control, water filtration and water infiltration. Lawns can withstand trampling and play that no other plant can handle. Lawns also need a lot less water than they are given. There are many low-water turf types available. With careful selection and efficient watering, lawns can be an important part of the low-water landscape.
Of the seven guiding principles of water-wise landscaping (a.k.a. Xeriscaping™), the most controversial involves the use of turfgrass in the landscape. At times it has seemed that water-wise landscaping might not allow for the use of turfgrasses at all. In fact, water-wise landscaping recognizes turfgrass as an integral component of the landscape.
Buffalo grass (right) is a good turf choice for Intermountain landscapes.
Benefits of Turfgrass
Turfgrass has some very specific benefits in the landscape. For example, it is the only landscape plant material that can withstand the stresses of traffic and mowing that are commonly applied to it. One can trample it, tear it, mow it, and it grows back! It is also the most practical surface for many types of outdoor recreation. And mowed lawns are a standard component of many urban fire control strategies. Turfgrass also provides many other environmental benefits. One such benefit is a reduction in the amount of surface runoff water. This is a key component to protecting water quality. An average golf course, for example, can absorb 4 million gallons of water during a 1-inch rainstorm. And a golf course or turf area can absorb far more than one inch of rain water without runoff, assuming it's not coming down too quickly. This is because a dense turf area can reduce runoff to virtually nothing. And when compared to a non-turf area (like a garden or agricultural field), grass areas can reduce runoff-induced soil erosion by up to 600 times (Whiting, et al., 2005). Turfgrass also reduces environmental pollutants. It traps dust and pollen and controls wind erosion of soil. Turfgrass also moderates temperature levels, which can reduce the amount of energy used for home cooling in the summer months. The soil microbes associated with growing turfgrass also work to break down pollutants in the environment such as air contaminants washed out by rainstorms, pesticides, and pollen. Turfgrass can be a practical and beautiful component of a water-wise landscape. As a design component, turfgrass invites participation in the landscape while providing unity and simplicity (Welsh, 2001).
Using Turfgrass in a Water-Wise Landscape:
Only use turfgrass in areas where it is functional. These areas may include play areas, areas receiving traffic, and areas needing temperature, noise, or dust mitigation. If the only time a turf area receives traffic is when it's mowed, perhaps a lower maintenance plant would work in that location.
Consider choosing turfgrass species with lower water requirements. In Utah, certain varieties of different turfgrass species perform better. These may be found in the bulletin Turfgrass Cultivars. This bulletin also discusses the characteristics and applications of commonly used turfgrass species in Utah. Another good resource is the Turfgrass Water Conservation Alliance (www.tgwca.org).
Consider using non-irrigated turfgrass areas. If the turfgrass is not performing a functional role, does it really need to be irrigated? Many turfgrasses can withstand considerable drought stress by entering dormancy (turning brown). When conditions improve, they will green up again.
Do not plant turfgrass in narrow, small, or oddly shaped areas that are difficult to irrigate efficiently. In these types of locations, there are many other plants that are more practical choices.
Hydrozoning in a water-wise landscape certainly applies to turfgrasses as well as other plants. Plan and design irrigation systems so that turfgrass areas are irrigated separately from other landscape plants. Also, become familiar with the actual water requirements of the turfgrass and don't exceed them.
Use cultural practices that will improve turfgrass water use efficiency. For example, mowing at a height of 2 ½ or 3 inches will encourage deeper rooting and improved heat and drought tolerance. Proper fertilization will also support healthy turfgrass and allow it to withstand the stresses of heat and drought better. Returning grass clippings when mowing also helps to reduce evaporation of water from the soil surface.
When these guidelines are followed, turfgrass becomes an appropriate, practical, and beautiful component of the water-wise landscape.
Water-Wise Landscaping Principle # 5: Mulch
Mulch can provide many benefits in water-wise landscapes. Mulch covers the soil and prevents crusting, compaction, and water evaporation, while also providing an important visual design aspect. Choosing the right mulch for the situation is dependent on plant selection, watering regime and site use.
Mulch can provide many benefits in water-wise landscapes. Mulch covers the soil and prevents crusting, compaction, and water evaporation. In fact, mulching around trees, shrubs, and in flower beds can result in a ten-fold reduction in evaporative water loss from soil. Reducing soil water loss means more water is available to plants and less water needs to be provided. Mulch also reduces the number of weeds in a water-wise landscape by preventing light-induced germination of weed seeds. With fewer weeds, less cultivation is required, which can prevent damage to plant roots, soil structure, and soil organisms. In addition, mulch moderates soil temperature and protects plant roots. In winter, moderation of soil temperature can prevent plants from heaving out of the ground due to freezing and thawing. Mulch also can be an important visual design element in a water-wise landscape, and it is used along walkways, in plant borders, and for color and structure in a landscape or garden.
Organic mulches include materials such as wood or bark chips, shredded bark, nut shells, pine needles, or other discarded plant parts. These materials have the potential to enhance soil structure, increase soil fertility, prevent compaction, and increase soil organic matter as they break down and are incorporated into the soil. Mulch is a great way to recycle yard waste, such as pruned woody plant materials, fallen leaves and needles, and even grass clippings. To ensure adequate water infiltration and aeration and to slow decomposition, make sure mulch particles are larger than the underlying soil particles (usually larger than a half inch in diameter).
Recycled plant materials must be free from weed seeds, disease-causing organisms, and pesticide and herbicide residues. You can either use disease-free plant parts that have not been chemically treated, or you can compost your mulch before use. Composting results in controlled decomposition of organic materials through the activity of microorganisms and generates enough heat to kill weed seeds and disease organisms. Composting also may break down some pesticides that can injure growing plants.
In most cases, use of organic mulch increases the nutrient fertility of the underlying soil and decreases the need for fertilizer application to mulched plants. However, the use of fresh wood or bark as mulch may lead to temporary nitrogen deficiency because microorganisms that decompose these high carbon content materials use up nitrogen that otherwise would have been available to the plant. Nitrogen loss can be avoided by using composted mulch or by adding nitrogen at a rate of 1-2 lbs actual N per 1000 ft2.
Over time, organic mulches break down and will need to be replenished. Replenishment can be accomplished simply by adding more mulch over the top of the decomposed mulch material. Before adding new mulch, roughen up the old mulch layer to prevent formation of a water-impervious surface between old and new mulch.
Decomposition of organic mulches sometimes can lead to nitrogen deficiency. Watch plants for telltale signs of nitrogen deficiency. If you notice yellowing that starts in older leaves, as well as decreased vigor, replace lost nitrogen using the fertilizer rate listed above.
Inorganic mulches consist of non-plant materials and may include a variety of different kinds of rock or gravel. Different sizes and colors of inorganic mulches are available. The decision about which to use will depend upon the kind of landscape, the reason for its use, and its availability. Examples include gravel or crushed stone, lava rock, recycled tumbled glass, and cobblestones of different sizes, shapes, and colors. The size of inorganic mulch particles should complement the scale of the landscape. For example, cobblestones work great in an expansive formal or naturalized setting or in a rock garden, but would be overwhelming in a small flower bed. Inorganic mulches provide the same benefits as organic mulches, including moisture retention, temperature moderation, and prevention of compaction. In addition, inorganic mulches provide excellent drainage that is often required of drought-adapted plants. Inorganic mulches do not decompose and need to be replaced infrequently. The disadvantage of inorganic mulch is that it does not add to soil fertility or organic matter, and plants will need to be monitored for signs of nutrient deficiency and fertilized accordingly.
Apply organic mulch to a depth of 3 to 4 inches, and inorganic mulch to a depth of 2 to 3 inches. A 2-inch thick layer of mulch requires about 6 cubic yards of material per 1000 square feet of area. Leave a few inches of mulch-free area around the base of woody plants to prevent root collar diseases and rodent damage. The best time to apply mulch is immediately after planting in the fall, or in the spring after the soil has warmed.
A weed barrier may be placed on the soil surface before using either organic or inorganic mulch material. The best choices are landscape fabrics of various types that allow air exchange and water infiltration. Plastic sheeting should be avoided because it tears easily, may generate excessively high root-zone temperatures in direct sun, and interferes with water and air exchange with the soil. Apply landscape fabric in strips over the soil, overlapping strips about 4 inches. Place mulch material over the weed barrier. Decomposed organic mulch will favor the growth of weeds on top of the weed barrier and should be replaced rather than replenished as needed. Under normal conditions, fabric weed barrier should last about 5 years.
Water-Wise Landscaping Principle # 6: Efficient Irrigation
In Utah, urban landscape irrigation accounts for 50-65% of the annual municipal water use, and much of it is applied in excess of the plant's needs. Scheduling irrigation according to landscape plant water needs can reduce excess water use. In addition to conserving water, proper irrigation can encourage deeper root growth and healthier, more drought tolerant landscapes.
An important component of water-efficient landscaping is creating hydrozones for your irrigation needs. To provide adequate water to all plants without over or under-watering some, group plants with similar irrigation needs in one zone. Once your plants are grouped into zero, low, medium and high water groups, you should plan your irrigation schedule to apply the appropriate amount of water to each zone. You can learn a great deal about plant-water requirements simply by observation. Signs, such as wilting, will let you know when many landscape plants require watering, but be careful not to overdo it. Plant roots need just as much air as water and you don’t want to drown them. If you are using an automatic irrigation timer, be sure to adjust it seasonally as the weather changes. A great deal of water is wasted when automatic irrigation systems are continually programmed for the hottest part of the summer without adjusting for times when temperatures are cooler and more natural precipitation is occurring. Another important aspect of irrigation planning includes routine maintenance of the system. Monthly examination of the irrigation system, while in use, will help you to find and repair any broken, misaligned, or clogged sprinkler heads and keep your system running efficiently.
Drip Irrigation systems consists of plastic pipes with emitters that deliver water directly to plants. These types of systems are great for water-efficient landscapes as water goes directly to the plants roots and is not wasted on areas that do not need to be watered. Drip irrigation can be used to water shrubs, trees, perennials, annuals and even vegetable gardens and potted plants.
Benefits of drip systems include:
- Minimizes disease by minimizing water contact with plant parts
- Avoids watering soil in between plants, thus reducing water use and weed growth
- Saves time, money, and water due to higher efficiency
- Increases effectiveness on uneven ground
- Reduces leaching of water and nutrients below root zone
- Maintains a desirable balance of air and water in the soil
- Provides a more even soil moisture than the often wet-to-dry fluctuations of sprinklers
Irrigating Lawn Areas
Turfgrass has shallower roots than other landscape plants and therefore should be irrigated more frequently, but not as deeply as other landscape plants. Consider using turfgrasses with lower water requirements to reduce water use even further. Plan and design irrigation systems so that turfgrass areas are irrigated separately from other landscape plants. There are several resources available to determine the appropriate watering schedule for turf areas in Utah.
Weekly Lawn Watering Guide from the Utah Division of Water Resources
Outdoor Watering Guide from the Utah Division of Water Resources
Irrigating Trees and Shrubs
Trees and shrubs have much deeper and more extensive root systems than turfgrass so they should be watered less frequently but for longer periods of time. The optimum time to water is just before you can observe any water stress. Therefore, it is important to determine sub-surface soil moisture. Soil moisture can be determined using a soil moisture probe.
Trees or shrubs should be watered to a depth of 18-20 inches. The amount of water to apply in any situation depends on the soil type. Sandy soils absorb water the fastest (about 2" per hour), followed by loam soils (3/4" per hour). Clay soils have the slowest absorption rate (1/2"per hour). By allowing water to penetrate deeper into the soil profile, you are encouraging deeper rooting and a more drought tolerant plant. Frequent, light irrigation will lead to plants that have a shallow root system and that are more prone to water stress. When using sprinkler systems about 1/2 -1 inch of water may be required weekly for shrubs and smaller trees (<4" trunk diameter). For drip irrigation about 5-50 gallons of water may be required. These amounts would be higher in southern Utah and lower in northern Utah and would also depend on plant size. Large trees (>4" trunk diameter), depending on the size of the tree, may require hundreds of gallons of water per week. Water newly planted trees and shrubs more frequently until the root system is established. Also, mulch and control weeds and grasses around the trunk of trees and shrubs to reduce competition for water and nutrients.
Maintaining an Irrigation System
Irrigation system maintenance is necessary to ensure the most efficient use of water that is being applied. Irrigation controllers should be checked at the beginning of each growing season before running sprinklers for the first time.
Programming: Set-up an irrigation schedule. The following basic irrigation schedule is recommended for use in Utah. Consult USU county extension offices for irrigation schedules that are directly applicable to your county
Inspect Sprinkler System: Once the irrigation schedule is programmed, inspect the sprinkler system by checking the valves,sprinkler heads, and emitters. Before running the system, remove the last sprinkler head in each line and let the water run for a few minutes to flush out any dirt and debris. Replace the sprinkler head and turn the system on, running one valve at a time.
Inspect Drip System: As with sprinkler systems, flush the drip system before running it by removing the emitters and letting water run through the tubing for a few minutes to flush out any dirt and debris. Replace emitters and run the system, one valve at a time, to check for problems.
Winterization: Basic winterization of a sprinkler system is quite simple. The water supply should be turned off at the main valve and the irrigation controller should be set to the “rain” or “off” setting. Each valve should be turned on to release pressure in the pipes and water should be drained from the system to protect any components that could freeze. Your system may have drain valves that can be opened for drainage, or you may have to blow out the system using air. You may wish to have your irrigation system blown out by an irrigation professional.
- Check Your System: Check your water system at the start of the season to adjust any heads and make sure there was no damage over the winter. The Water Check program offers free irrigation checks in many Utah counties. To find out more, or to find out how to check your system yourself, go to the CWEL Water Check page.
Water-wise Landscaping Principle # 7: Landscape Maintenance
A benefit of established water-wise landscapes is they require less time and money to maintain than a traditional landscape. This assumes you have limited turfgrass to areas where it is practical, you have selected plants adapted to your climate, and you have grouped landscape plants according to their water, soil, and sun exposure requirements. Spend less time trying to manipulate plants to fit your conditions, and more time enjoying their beauty.
A benefit of established water-wise landscapes is they require less time and money to maintain than a traditional landscape. This assumes you have limited turfgrass to areas where it is practical, you have selected plants adapted to your climate, and you have grouped landscape plants according to their water, soil, and sun exposure requirements. In such a landscape, you will spend less time trying to manipulate plants to fit your conditions, and more time enjoying their beauty. Although the activities required to maintain a water-wise landscape are not different from those of a conventional landscape, the way you think about them will change as you reconsider your plant selections. The main activities of water-wise landscape maintenance are irrigation and irrigation system maintenance, weed control, fertilization, pruning, and pest and disease control. Keep in mind that newly planted landscapes will require much more “upfront” maintenance, especially regarding weed control, and that all landscapes require some maintenance, whether they are water-wise or not. With persistence and patience, your water-wise garden will become more self-sustaining and require much less of your time.
A weed is simply a plant out of place. With that in mind, any plant can be a potential weed if it crowds out or uses up resources needed for desirable plants. Some “weedy” plants become such a problem that they end up being declared “noxious” in a particular region. Controlling weeds is critical to maintaining a healthy water-wise landscape because weeds compete with desirable plants for nutrients, moisture, and sunlight. Remember that water used by a weed is unavailable to desirable plants. Weeds can be annuals (germinate, reproduce, and die in one season) or perennials (survive over many years). It is important to learn to recognize and classify weeds in the seedling stage because this will determine your best control options. Perennial weeds are especially difficult to control if you let them grow beyond the seedling stage because they establish deep root systems that are hard to eradicate. You may also find it helpful to learn to distinguish between weed seedlings and seedlings of self-sowing desirable plants, especially if you are using self-sowing plants to fill in some areas of your garden. Methods for controlling weeds include mechanical removal, physical barriers such as landscape fabric and/or mulch, and herbicides.
Mechanical removal of weeds can be accomplished by hand-pulling, hoeing, or tilling. Even though hand-pulling weeds can be tedious, if done on a regular basis before weeds go to seed, it is the least disruptive weed control method in established plantings. Hand-pulling works with either annual or perennial weeds, as long as you catch them in the seedling stage. It can be difficult to pull out the entire root system of an established perennial, and if you don’t, it can sprout again from the root or crown. Never leave annual or perennial weeds on top of soil or use as mulch after pulling because some persistent weeds can re-sprout from root crowns and root systems left on the ground. Annual weeds that haven’t gone to seed can be composted, but perennial weeds should always be discarded in the trash. Hoeing and tilling are alternatives to hand-pulling, but care must be taken around established plantings so you don’t disturb or destroy the roots of desirable plants.
Mulches should be used around landscape plants to inhibit weeds and conserve water. Mulches can be organic materials such as composted wood chips, pine needles, or grass clippings, or they can be inorganic materials such as crushed stone or gravel. Weed seedlings that do come up in mulched areas are much easier to hand-pull, as long as you catch them early. Organic mulches will need to be refreshed regularly as they slowly decompose. Do this by roughing up the old mulch and adding a light layer of new mulch over the top. Inorganic mulches need to be replaced infrequently.
Landscape fabric is another effective method for controlling weeds, but its use around landscape plants is controversial. It can interfere with air and water infiltration, and it may inhibit return of organic matter from decomposition of organic mulches to the soil. Landscape fabrics may discourage some desirable perennials from their natural tendency to grow and spread, and it can make division and replacement of these plants difficult. Fabrics also can girdle trees as they grow and trunk girth expands. The best use of landscape fabric is beneath 3 to 4 inches of mulch in unplanted areas like walkways, where they can form an effective barrier to weed growth.
The weed control method of last resort should be herbicide use. Of the many options available, pre-emergent herbicides and products containing glyphosate are among the safest and most effective. Pre-emergent herbicides are moved into the soil and activated by moisture. If they are applied in late fall or winter, moisture from either rain or snow precipitation should be adequate to activate them. If precipitation does not occur within three days of application, 1 to 2 inches of water should be applied to treated soil. Areas of your garden that are watered infrequently or not at all may not receive the full benefit of pre-emergent herbicide application unless you remember to water them in soon after application. Pre-emergent herbicides work by killing seedlings as they sprout, but they will eliminate all germinating plants, not just weeds. Use a pre-emergent herbicide only in areas that are, or will be, planted with rooted plants. Do not use them if you rely on self-sowing plants to fill in gaps in your perennial flower beds. Glyphosate products eliminate both grasses and broadleaf plants, and are applied directly to emerged, actively growing weeds. Glyphosate takes 7 to 10 days to have an effect. Do not allow glyphosate-containing products to contact desirable plants, and do not spray under windy conditions because spray drift can also cause unintentional damage to desirable plants. Always read the label for safe and effective use.
All plants require nutrients to grow and remain healthy, but many drought-tolerant native and adapted plants can get all the nutrients they need from a properly maintained soil environment. Many of our urban landscape soils, however, have been stripped of organic matter and the soil structure disturbed to the point where nothing but the most persistent weeds will grow. For this reason, it is a good idea to have your soil tested prior to installing landscape plants. (For information on soil testing and soil test results, see the following fact sheet: http://extension.usu.edu/files/publications/publication/HG-513.pdf ) Your county Extension office can provide information specific to your area. In most cases, amending soils with composted organic matter prior to planting will improve the fertility of your soil. Adding organic mulch to planted areas also helps to improve soil fertility over time. If part of your garden will be comprised largely of drought-tolerant native plants, organic amendments may be all they need to thrive. Many drought-tolerant plants have adapted to their arid habitats by growing slower than traditional landscape plants. Over-fertilizing these plants only weakens them and results in rank, unsightly growth. In fact, many of the penstemons and desert-adapted shrubs like Chrysothamnus nauseosus (Rabbitbrush) and Fallugia paradoxa (Apache Plume) thrive on neglect and require the excellent drainage provided by inorganic rock mulch and little to no supplemental fertilization.
Knowing the habitat your plants are adapted to is critical to understanding your plant’s needs. If you don’t know, err on the side of less rather than more nutrients, and watch plants closely throughout the growing season for signs of deficiency. Nutrient-deficient plants may develop yellow or discolored foliage. If this happens, simply add organic matter or a controlled-release type of complete fertilizer around the root zone, water in thoroughly, and watch for improvement. Other factors may affect the availability or movement of nutrients through the soil. Plants in sandy soils may need more frequent fertilization than plants in loamy or clay soils. Soils that are alkaline (high pH) may bind essential nutrients and make them unavailable. A soil test will provide this information and make recommendations for amending the soil. An alternative to soil amendment is to choose plants that are adapted to these conditions. Utah soils are often alkaline, and textures can range from rocky or sandy to silty loam or clay. Fortunately, plants native to our region have adapted to these conditions, and you can choose from a variety of native plants to fill almost any microclimate in your landscape. The key is to learn as much as you can about your yard and your plants. Paying attention to the needs of your landscape plants will make you a more successful gardener.
Controlling Plant Growth
Periodically, you will need to control the growth of your landscape plants by pruning, pinching or deadheading, and dividing. These activities will maintain your plants’ health and appearance by removing dead or undesirable growth, and by stimulating, reinvigorating, or re-directing their growth. Remember that providing only the amount of water or fertilizer plants need to maintain their health and vigor means less time spent controlling unruly growth. Some locally adapted native plants may quickly grow out of their space when provided with the relatively abundant resources available in a managed landscape. An example is Gutierrezia sarothrae (Matchbrush). Withholding water or nutrients will keep growth of this species in check.
Pruning is a way to control growth on trees and shrubs. Many forms of pruning exist, and the kind of cut you make depends upon the desired result and the growth habit of the plant. For example, most deciduous shrubs (shrubs that drop their leaves in fall) benefit from thinning cuts that open up their canopy and eliminate old or competing stems. Thinning cuts are made by cutting a branch back to its point of origin. The point of origin could be another branch or the main trunk, or it could be near the ground. Thinning can be used to shape or direct growth, but most often it is used to reduce bulk and restore the natural structure of the plant. A heading cut is more severe than a thinning cut, and removes part of a branch leaving a short stub above a bud. This type of cut stimulates a profusion of twiggy growth from a lateral bud just below the cut. It is used to stimulate new growth from a lateral bud to fill in a gap in the canopy, or to increase flower production in some shrubs. Sometimes it is mistakenly used when a thinning cut would have been a better choice. Overuse of heading cuts can ruin the natural shape of a tree or shrub. Shearing is the most severe type of heading cut and involves cutting a plant’s outer foliage to create an even surface. Only certain trees and shrubs will benefit from this type of cut.
Shearing can be used to create a hedge or screen with closely spaced plants. Some woody plants can be treated like herbaceous perennials and sheared almost to the ground to control their growth or to restore them to a more natural shape. Most pruning should be done in late winter or early spring before spring growth begins. For plants that flower on last year’s growth, prune after flowering. With only a few exceptions, most native conifers require no pruning. For example, junipers are highly valued for their natural shape. Junipers that have outgrown their space should be removed rather than pruned. (For more information on pruning trees, see the following extension bulletin:http://extension.usu.edu/files/publications/publication/NR_FF_004.pdf.)
The bloom time of some annuals and herbaceous perennials can be extended by removing flowers as soon as they start to decline. This is called deadheading, and some plants can be stimulated to repeat bloom when you remove the spent flowers. In the case of plants with a flower on a single stem, cut back the entire stem to avoid a gangly, headless stem. If you don’t deadhead plants that repeat bloom, the plant will set seed, signaling the end of flower production for the season.
Some herbaceous perennials can be sheared by one half to two thirds after they have gone dormant in the fall. This will remove unsightly stems and rejuvenate plants that have become gangly and have reduced flowering. Consider delaying cleanup until late winter for plants that have persistent and attractive stems and seed heads. Plants like Gaillardia (blanketflower), Astilbe (false spiraea), and many native grasses can add structure, texture, and color to an otherwise drab fall/winter landscape.
Division is another way of rejuvenating herbaceous perennials that have become weakened by age or overgrowth. A sign that your plants need dividing is when flower production is reduced and the stems become thin and nonproductive. Perennials are divided by digging up the plant, taking care to dig around, not through, the root system. Using a shovel, two pitchforks, or a sharp blade, pry the plant root system apart to separate into two or more separate plants. Plant roots should be kept cool and moist during this process, and new plantlets should be installed and watered in soon after division. Most perennials need to be divided every three to five years.
Pest and Disease Control
The best way to fight insect or disease problems is to prevent them from happening in the first place. When a system called integrated pest management (IPM) is used, you will rarely need to spray chemical-based pesticides to control pests in your yard. IPM emphasizes prevention and involves several strategies to control pests, including using landscape plants adapted to your climate, diversifying your planting choices, and maintaining optimal plant health by not over-fertilizing and over- or under-watering. Also keep the landscape free of plant debris, and regularly inspect landscape plants for problems. When potential problems are found, contact your local Extension office for help in diagnosing and correcting the problem. (See the following USU Extension Web site for detailed information on plant pest control, http://utahpests.usu.edu.)