Selecting turf and ground covers
A well-designed landscape that includes trees, shrubs, annuals, ground cover and turf can be beautiful to casual strollers who take it all in as they walk. However, the placement of these elements determines whether the professional grounds manager considers it a dream landscape or an 8-to-5 maintenance nightmare.
Many have written about the virtues of planning ahead. If you can work with the landscape architect when he or she is designing the landscape, you're in a good position. The more thought that goes into designing the landscape with the maintenance budget in mind, the better off you'll be when it comes down to balancing your budget.
Here we'll discuss how to work with a landscape architect to create a maintenance-conscious design, what situations favor turf and which areas lend themselves to ground covers.
You and the architect The best of all design teams consist of the client, the landscape architect, the landscape contractor and the grounds manager. Here's how everyone works together in the ideal world:
* Preliminary planning. As a grounds manager, you work to determine the nature and scope of the project. Nail down financial and time budgets. Include the expenditure for constructing the project as well as anticipated maintenance costs down the road. For example, irrigation-system maintenance will be easiest if you use irrigation parts with which you are familiar and have in-stock. A 14- to 14.5-foot-wide turf area accommodates a sprinkler nozzle with a 15-foot throw and a 36-inch-wide mower.
* Construction documents. The architect prepares construction documents from the schematic design. The documents make the design a biddable, buildable and, you hope, maintainable entity. Make sure these documents represent exactly what you want. If you know a better way to install turf or ground cover, say so at this point. Seed can be cheaper than sod, but only if you can control irrigation and weed problems. These are specific areas an architect might overlook.
* Construction phase. Overseeing critical areas of landscape establishment helps ensure that installers carry out the agreed-upon plan. Pressure-test irrigation main lines and laterals before backfilling. Apply pre-emergence herbicides, and be sure sod is rolled correctly. Have the contractor prepare as-built drawings that reflect any changes from the original design.
* Maintenance specifications. As the grounds manager, you need to understand the architect's vision of the mature design. If you've been on the site for several years, you can work with the architect to incorporate his or her ideas into your existing practices. However, if you were hired after the architect finished, ask him or her for maintenance specifications, including the architectural design intent. Design intent tells you whether the architect intended for you to formally shear the newly installed boxwoods or leave them alone to create a more informal setting, and specification should tell you how to do it. Specifications also are helpful in maintaining a consistent landscape through maintenance staff changes.
Both turf and ground covers have their place in a maintenance- and water-conscious landscape. Here are some points to consider when you need to choose between the two.
Turf design guidelines Turf is the best surface for sites where people will be active in the area. Sports fields, playgrounds, parks and sunbathing areas all need turf. However, the passive or visual use of turf has drawn flak in California and other Western states where diminished water resources have been near critical levels in recent years. These states are discouraging turf use in some areas.
You can counter turf criticisms by planting the correct species, placing it intelligently and irrigating it conservatively.
* Knowing your species options is the first step in choosing the best turf for your site. For species selection criteria, consult a generic text on turfgrass, such as A.J. Turgeon's Turfgrass Management (Reston Publishing, 1985) or J.B. Beard's Turfgrass Science and Culture (Prentice Hall, 1973). Once you've selected your species, investigate varieties and cultivars for site-specific qualities. Your local extension agent can provide you with additional information. After all, the best turfgrasses for your site are those that are proven performers in your location.
* Placing turf within durable boundaries will make management easier. For long life, concrete mow strips are best. You can color or texturize; it need not be ugly. A good minimum border width is 6 inches. Anything narrower is hard to effectively form and pour. Always reinforce concrete with at least No. 2 rebar (also called 0.25-inch pencil rod). Overlap ends of individual lengths at least 12 inches. As with all concrete work, provide subsurface sleeves where you anticipate future work and set irrigation heads at least 1 inch off concrete edging to help prevent damage from edgers. Remember that all permanent objects placed on turf-such as backflow-prevention devices, pedestal controllers and valve boxes-should have maintainable edges that facilitate mowing and edging.
* Irrigate turf with 100-percent coverage. Myriad products are available to help you reach this goal, so don't compromise. Design turf to irrigation, not vice-versa. As a general guideline, use pop-up heads on triple-swing-joint riser assemblies (with street elbows) for servicing ease. Other risers that prevent damage to heads are flex risers and cut-off risers. Try to use a minimum 12-inch depth for irrigation lateral lines. Don't push established design standards in head spacing. Square spacings should be 100 percent of rated radius, and triangular spacings should be at least 60 percent of rated diameter.
Make sure the installation contractor adjusts the flow control on each remote-control valve to help prevent misting and ensure timely valve closure. Specify check valves in descending irrigation laterals or in individual low heads on sloped or mounded turf areas to help prevent low-head drainage.
Organize turf areas with different needs on separate irrigation circuits. For example, separate sunny and shady areas, top of slopes, middle of slopes, bottom of slopes and annual beds and shrubs. This arrangement addresses the different water needs of these areas and helps prevent overwatering and runoff.
On mounded or sloped turf, run irrigation laterals across the slope rather than vertically. Irrigate more on top of the slope and less as you progress down. Doing so accounts for runoff.
Ground cover considerations If you use turf on active areas, ground covers can balance the design in outlying, mainly visual areas. In California, for example, designers use ground covers for varying purposes from stabilizing erodible hillsides to providing fire-retardant buffers (for example, Carpobrotus edulis-ice plant).
One of the best places to plant ground covers is around trees. You can accommodate trees in turf, but trees do present turf-maintenance problems. With ground covers around them, you provide a place for nutrient-rich tree litter and encourage deeper tree roots.
Ground covers come in a variety of colors, textures, forms and growth habits. Trailing African daisy (Osteospermum fruticosum), common in California, sets beautiful flowers in white to deep purple for most of the year. Baltica English ivy (Hedera helix 'Baltica') has a variegated white and green leaf and is far less aggressive and problematic than its large-leafed cousin, Algerian ivy (Hedera canariensis). Baby's tears (Helxine soleirolii) provide a green, soft, cloud-like texture in shady areas. Even vines, such as bougainvilleas, do extremely well trailing along the ground rather than climbing a trellis.
Because it spreads from individual plants, ground covers are less fussy about their irrigation needs, and you can use drip irrigation.
Mow ground covers as regularly as needed to keep them at an acceptable height. For woody ground covers, prune hard to keep them at the correct height.
If you choose to irrigate with spray heads, use 12-inch pop-ups along walks and turf interfaces because fixed risers can be a tripping hazard. Irrigate deeply and infrequently, especially when ground covers surround trees. For more information on ground covers that would be suitable for your site, contact your cooperative extension agent or nursery.
In almost every major landscape project, you'll be choosing between turf and ground covers. These guidelines should help you find a place for each.
Steve Frogley McGuirk is a landscape architect with Madrone Landscape Group (Soquel, Calif.).
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