Crabgrass 2008

17 March 2008

Virginia Cooperative Extension, Charlottesville/Albemarle County Office
460 Stagecoach Road, Charlottesville, Virginia 22902
phone: 434.872.4580   fax: 434.872.4578

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Crabgrass seed lies in the soil, waiting for the right temperature and moisture to emerge in lawns for another season. Crabgrass continues to be the number one pest in lawns worldwide. No matter how much effort you have taken in previous years to control crabgrass, our soils remain a veritable seed bank of crabgrass from years past. This warm-season summer annual grass germinates from seed prior to the first significant growth period of our lawn grasses. As annual plants are genetically programmed to do since they live such a short time, they grow like mad under optimal temperature conditions. Hence, a warm-season crabgrass plant has an inherent competitive advantage against cool-season lawn grasses (fescues, bluegrasses, and ryegrasses) and can even slug it out with perennial warm-season grasses (things like bermudagrass and zoysiagrass) because it gets a jump on them in early spring growth.

A picture of crabgrass.

Use your turf to maximize crabgrass control

Crabgrass requires sunlight to germinate, a requirement that we can use to our advantage. The lawn itself controls far more weeds than any chemical you will ever apply because the most weed control is gained by maintaining a dense turf canopy. If you were fortunate enough to survive the drought of 2007 with a reasonably dense lawn, spring weed pressure will be minimal. You still might want to use a standard preemergent (PRE) herbicide (a product that controls germinating plant seedlings), but it is unlikely your lawn will be swamped with weeds. If your turf stand is very sparse, then it is almost guaranteed that you will have significant weed pressure. So there is now a decision to be madedo you apply a PRE herbicide to control weeds OR do you apply new grass seed to fill in the gaps. For standard PRE herbicides available to most homeowners, there is no selectivity in control between weed or grass seed. So if the lawn is really thin, you will likely be better served to plan on a spring seeding over the next few weeks. You can still expect crabgrass pressure as the new grasses try to establish, but since the best weed control comes from the grass in your lawn and not the chemicals applied, this is likely the best approach. For those of you working with a professional lawn care operator, there are PRE options (chemical names of siduron and quinclorac) available to them that can be applied at spring seeding of cool-season grasses (not warm-season). This is another of the advantages available to homeowners when working with trained professionals.

What PRE herbicides are readily available to homeowners?

There are many trade names of products on the market, so while it takes a little extra effort to look for the complicated common chemical names, it is the safest way to identify the product you are looking for. The following chemicals can most often be found at stores that deal with specialty products for lawns and landscapes, and at least a few of them will likely be available at your big-box retailers. Look for these chemical names under the Active Ingredient label of the prospective product: benefin, benefin + trifluralin, dithiopyr, pendimethalin, and prodiamine.

There is also an organic weed control product on the market as well: corn gluten meal (CGM). CGM works by releasing a protein that slows development of weed seedling roots leaving seedlings vulnerable to drought. In periods of extended rainfall CGM will fail to control weeds and its length of activity is very short-lived (a few weeks) as compared to standard synthetic chemistry which may last 120 days. If you are trying to establish turfgrass seedlings, CGM can harm them similar to synthetic chemistries, so consider if seeding is desired. CGM works best in northern climates and in lawns that have good turf density. Labeled rates of CGM treatments will deliver approximately 1 pound of water insoluble nitrogen per 1000 sq ft, making CGM another offering in the group of products known as weed and feed materials. For noticeable effects on crabgrass populations, 2 to 3 applications are needed in Virginia. Thus, 2 to 3 pounds of nitrogen is added to the turf in the spring. In the north, this added fertility tends to increase turfgrass competitiveness with crabgrass and reduce crabgrass infestation. In southern areas like Virginia, this added fertility in the spring can be injurious to tall fescue and lead to decline in turf during the stressful summer months. This decline in turf due to over fertility from CGM will leave openings in the turfgrass canopy and might actually promote weed infestation. For the Virginia do-it-yourselfer interested in CGM, we suggest you use CGM only once in early spring and add a half rate of synthetic preemergence crabgrass herbicide. Be sure that the herbicide does not contain any fertilizer. In so doing, you can rest assured that you have reduced your use of synthetic pesticides by using the half rate and reduced excessive nitrogen by using only one treatment of CGM.

Timing of PRE applications?

A valuable visual tool in the landscape that typically allows us to optimize the timing of PRE herbicides for homeowners is forsythia. Its blooming can never be taken as an absolute signal of pending crabgrass emergence but it works in most years and research has found that the time when forsythia starts to drop its blooms is when PRE herbicides need to be in place in order to maximize crabgrass control. Do not be alarmed if your lawn care operator has applied earlier because due to sheer numbers of lawns to treat, there is no way they could make all the applications to their customers according to forsythia bloom. The PRE herbicides they are using have soil activity for 6-8 weeks that will address a broad window of crabgrass germination potential and it is better to be extra early rather than late when applying preemergence herbicides for crabgrass control.

Post-treatment considerations?

One thing required for all PRE herbicide applications is to water the product into the soil with either a suitable rainfall or irrigation event. The only way the product works is if it gets into the top of the soil profile to form a chemical barrier that germinating seedlings penetrate. Appropriate moisture is critical to optimize herbicide efficacy. And remember to keep all products on the turf and off hardscapes. This is the easiest way to protect our water resources.

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For more information about this and other landscape topics contact your local Virginia Cooperative Extension office. The local Virginia Cooperative Extension office numbers are Albemarle 872-4580, Fluvanna 591-1950, Greene 985-5236, Louisa 540-967-3422, and Nelson 263-4035.

Planting Trees and Shrubs

3 March 2008

Virginia Cooperative Extension, Charlottesville/Albemarle County Office
460 Stagecoach Road, Charlottesville, Virginia 22902
phone: 434.872.4580   fax: 434.872.4578

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Itching to get out and plant something? By following some basic planting guidelines you can save yourself and your plants some trouble down the road. The cornerstones of successful tree or shrub planting are plant and site selection, site preparation, plant preparation, and care after planting. Begin by selecting trees and shrubs that are well adapted to conditions of individual planting sites. Poorly sited plants are doomed from the start, no matter how carefully they are planted.

Children gardening.

Test your soil drainage before planting. Dig a test hole as deep as your planting hole and fill with water. If water drains at a rate of less than one inch per hour, consider installing drainage to carry water away from the planting hole base, or moving or raising the planting site. Also consider using more water-tolerant species. For trees, try red maple, sycamore, bald cypress, willow oak, or river birch. For shrubs, try inkberry, redtwig dogwood, and buttonbush. Avoid other dogwood species, azaleas, boxwoods, Japanese hollies, and other plants that don't like "wet feet" where drainage is poor.

Examine soil for compaction before planting. If soils are compacted, consider replacement with a good loam soil, or incorporation of several inches of an organic material such as composted yard waste to a depth of at least 8 inches over the entire planting area. Do not incorporate small quantities of sand because compaction will increase and drainage will decrease.

Dig shallow planting holes two to three times as wide as the root ball. Wide, shallow holes encourage horizontal root growth that trees and shrubs naturally produce. In well-drained soil, dig holes as deep as the root ball. In poorly drained heavy clay soil, dig holes one to two inches shallower than the root ball. Cover the exposed root ball top with mulch.

Do not dig holes deeper than root balls or put loose soil beneath roots balls because loose soil will compact over time, leaving trees and shrubs planted too deep. Widen holes near the soil surface where most root growth occurs. Score walls of machine-dug (auger, backhoe) holes to prevent glazing.

Backfill holes with existing unamended soil. Do not incorporate organic matter such as peat moss into backfill for individual planting holes. Differences in soil pore sizes will be created causing problems with water movement and root growth between the root ball, planting hole, and surrounding soil. Backfill half the soil and then water thoroughly to settle out air pockets. Finish backfilling and then water again. Cover any exposed root ball tops with mulch.

Closely inspect the wrapping around root balls of B&B (balled and burlapped) trees and shrubs. Growers use many synthetic materials, as well as burlap treated to retard degradation, to wrap root balls. Many of these materials will not degrade. To insure root growth into surrounding soil, remove pinning nails or rope lacing, then cut away or drop the wrapping material to the bottom of the planting hole, backfilling over it.

Wire baskets used to protect root balls degrade very slowly underground. Remove at least the top 8-12 inches of wire to keep equipment from getting caught in wire loops, and surface roots from girdling. Remove all rope, whether jute or nylon, from trunks. Again, degradation is slow or nonexistent, and ropes can girdle trunks and roots.

If roots are circling around the root ball exterior, cut through the roots in a few places. Cutting helps prevent circling roots from eventually girdling the trunk. Select trees grown in containers with vertical ribs or a copper-treatment on the interior container wall. These container modifications and treatments minimize circling root formation.

Remove tags and labels from trees and shrubs to prevent girdling branches and trunks. Good follow-up watering helps promote root growth. Drip irrigation systems and water reservoir devices can facilitate watering.

Mulch, but do not over mulch newly planted trees and shrubs. Two to three inches of mulch is best. Use less if you are using a fine material, more if the material is coarse. Use either organic mulches (shredded or chunk pine bark, pine straw, composts) or inorganic mulches (volcanic and river rocks). Keep mulch from touching tree trunks and shrub stems. This prevents disease and rodent problems if using organic mulches, and bark abrasion if using inorganic mulches.

Only stake trees with large crowns, or those situated on windy sites or where people may push them over. Stake for a maximum of one year. Allow trees a slight amount of flex rather than holding them rigidly in place. Use guying or attaching material that will not damage the bark. To prevent trunk girdling, remove all guying material after one year.

Most trees should not have their trunks wrapped. Wrapping often increases insect, disease, and water damage to trunks.

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For more information about this and other landscape topics contact your local Virginia Cooperative Extension office. The local Virginia Cooperative Extension office numbers are Albemarle 872-4580, Fluvanna 591-1950, Greene 985-5236, Louisa 540-967-3422, and Nelson 263-4035.

Garden For Pleasure

25 February 2008

Virginia Cooperative Extension, Charlottesville/Albemarle County Office
460 Stagecoach Road, Charlottesville, Virginia 22902
phone: 434.872.4580   fax: 434.872.4578

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Today is Pleasure Day so how are you celebrating? Are you out in the garden with your kids planning your spring landscape renovation and pruning your butterfly bushes? Maybe you are not waiting for spring and putting fresh pansies in the ground to brighten up your garden or maybe you have postponed all of this to go to a hockey tournament or a basketball game.

Children gardening.

Today's hectic lifestyles leave families little time to spend together; however, gardening offers a perfect opportunity for a family to share and learn together. Many activities are suitable for family time in the garden, such as:

• Plant a tree to celebrate a birth. A tree's growth is much like a child's. It starts small and young, as a seedling. It needs nourishment and watering. Like a young child, a tree goes through growth spurts, passing through juvenility and entering maturity. In maturity, it is able to share with others its fine attributes, such as shade to cool and add comfort to a yard or home, leaves to help make soil-building compost, and sturdy branches from which young children can swing.
• Your child can see his or her own growth reflected in the growth of the tree and can appreciate the length of time it takes for a tree to grow to maturity. The love of trees your child gains now will carry on through adulthood.
• Learn the names of plants. Spending time in the garden to learn about plants can be fun for parents and children both. In addition to learning about food crops and beautiful flowers, this time is a perfect opportunity to learn which plants or plant parts can be potentially poisonous and how to enjoy the plants safely.
• Plant a vegetable garden. The rewards of a vegetable garden are as exciting to adults as they are to children, giving both a sense of accomplishment. Sharing the joy and excitement or even the disappointment and failure of a vegetable garden strengthens family ties.
• Make crafts from garden harvests. Projects, such as making bird houses from gourds grown in the family garden or arranging dried flowers, offer times of sharing for family members.
• Share gifts of the garden. Giving gifts of handmade crafts and treasures from the garden is extremely satisfying, and I have never met anyone who was not delighted in receiving such gifts. Even fresh produce, such as tomatoes, squash, and green beans, make terrific gifts for people who do not have a garden. Offering these gifts gives adults and children alike an opportunity to show they care about others.

The garden is a fertile ground of opportunities for families to grow together and learn more about each other while tending the garden. It offers the opportunity for adults and children to share ideas -- to talk and, most importantly, to listen to each other and, by working together, to communicate the many messages that must be said without words. Gardening develops self-esteem, a sense of nurturing, and the quality of generosity. The garden is a wonderful family room!

Start now to involve your child in the planning of your spring garden. There are many books for children to educate and excite them about gardening. Seed catalogs can be a source of fascination and are perfect for craft projects after the plants have been ordered.

If you wish you had someone to team up with try contacting your local 4-H club to see if they have plans for gardening projects this spring. Maybe you can help get one started. Each county Extension office has a 4-H Extension Agent who helps these sorts of clubs get organized with the help of local adult leaders. We are always looking for new leaders and for more kids to participate.

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For more information about this and other landscape topics contact your local Virginia Cooperative Extension office. The local Virginia Cooperative Extension office numbers are Albemarle 872-4580, Fluvanna 591-1950, Greene 985-5236, Louisa 540-967-3422, and Nelson 263-4035.

Invasive Plants

18 February 2008

Virginia Cooperative Extension, Charlottesville/Albemarle County Office
460 Stagecoach Road, Charlottesville, Virginia 22902
phone: 434.872.4580   fax: 434.872.4578

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Invasive nonnative plants are the subject of a considerable amount of attention and debate and stories about invasive plants are now common in the popular media. As purchasers of non-indigenous plants that have the potential to invade natural areas, consumers are links in the distribution chain of invasive plants. Other links are those who import, propagate, transport, and sell non-indigenous plants. Ultimately, the result is a potential impact on our natural environment.

An Ailanthus tree.

A review of catalogs from U.S. wholesale growers shows that at least 50 percent of woody plant species are native to regions outside of North America. If one were to consider the species sold in any one area, the proportion of nonnative plants (not native to that particular ecosystem) would certainly be much higher. Most non-indigenous species have graced our landscapes with beauty and untold beneficial environmental effects. However, a significant proportion of these are invasive. Data from six nongovernmental organizations indicated that 34 percent to 83 percent of the total number of invasive taxa (species, varieties, or cultivars) in the U.S. had a horticultural origin.

One of the most lucrative areas of ornamental plant sales is the introduction of new-to-the-trade plants. These novel introductions fuel plant sales, stimulate efforts to seek out new introductions, many from outside the U.S., and yield substantial profits. A quick glance at most garden catalogs and mail order websites verifies this trend, a trend that encourages plant exploration and has the potential to exacerbate the invasive plant problem.

Environmental groups, regulatory entities, and those in the ornamental horticulture industry (including consumers) are the key stakeholders in the invasive ornamental plant arena. The different interests of key stakeholders can lead to conflicting viewpoints that may constitute standoffs without an apparent or imminent compromise. The perspective of an environmentalist is that nonnative invasive species represent a threat to nature. To ornamental industry personnel, profits and jobs are potentially threatened without the import and sale of these nonnative plants. As a result, the invasive nonnative plant topic evokes emotional as well as scientific or quasi-scientific debates. The lack of a complete understanding of invasion biology terminology and concepts is a significant impediment to meaningful dialogue and the resolution of differences.

What is an invasive plant?

The legal definition of an invasive species, and the official position of the U.S. government, is An alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health. (http://www.invasivespeciesinfo.gov/laws/execorder.shtml) The legal definition of alien species, also termed non-indigenous or exotic, is with respect to a particular ecosystem, any species, including its seeds, eggs, spores, or other biological material capable of propagating that species, that is not native to that ecosystem. In a strict interpretation, any plant outside its native ecosystem is considered non-indigenous. For example, black locust (Robinia pseudoacacia) is a common tree native to the central Appalachian and Ozark Mountains but is considered an invasive species in California. Thus, plants native to one state can be invasive in another state.

Predicting invasive potential

Predicting which non-indigenous plant species will become invasive is one approach to keeping potentially invasive species out of commerce, thereby eliminating the threat to the native environments. However, predicting which species will be invasive in a particular area is a very difficult task due to the complexity of nature. There has been an abundance of work to determine the plant characteristics and ecological factors that lead to plant invasion. At present, the most reliable and powerful predictor of a species invasiveness is its record of invasiveness in other nonnative sites. Many prediction schemes have been developed to assess the potential of plant taxa to be invasive. These approaches to understanding the invasive potential have significantly increased the ability to predict which taxa will be invasive.

Why should we be concerned about invasive plants?

In short, nonnative invasive plants have negative effects on biodiversity (i.e., the rich genetic resource of flora, fauna, and microbes) at the ecosystem level and the community and population levels. Examples of how invasive plants threaten the health of natural areas are 1) replacement of diverse systems with single stands of nonnative species, 2) changes in soil chemistry, land form processes, fire regime, and hydrology, 3) competition with endangered species, and 4) competition with and displacement of native fauna.

What can landscape professionals and gardeners do?

Information on the Internet can be overwhelming, confusing, and inconsistent. There are a few good sites that include ranking systems of invasive impacts based on scientific observation. NatureServe, a nonprofit conservation organization, has a current data-based assessment of non-indigenous plant species (http://www.natureserve.org/explorer/servlet/Natur eServe?init=Species). Other sources that have developed rankings relevant to Virginia residents are the Virginia Native Plant Society in conjunction with the Virginia Department of Conservation and Recreation (http://www.dcr.virginia.gov/natural_heritage/invsppdflist.shtml) and the SoutheastExotic Pest Plant Council (http://www.se-eppc.org/). These groups have ranked species according to their perceived and observed threats to the environment.

Finally, if a gardener would like to use a native plant as an alternative for a specific nonnative plant, there are books and websites that have this information (e.g., Native Alternatives to Invasive Plants, Brooklyn Botanical Garden, 2006; http://www.dcr.virginia.gov/natural_heritage/nativeplants.shtml [click on Native Plant Tables]; http://www.mdflora.org/publications/invasives.htm).

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For more information about this and other landscape topics contact your local Virginia Cooperative Extension office. The local Virginia Cooperative Extension office numbers are Albemarle 872-4580, Fluvanna 591-1950, Greene 985-5236, Louisa 540-967-3422, and Nelson 263-4035.