Articles in this issue:
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The continuing drought and extremely low soil moisture levels are contributing to browning foliage of many evergreen species such as spruce, fir, pine and juniper. Brown needles were apparent this spring from winter desiccation and brown-ing has continued during the summer. Summer drought injury is charac-terized by tip die-back of needles, progressing from the top of the plant downward and from outer branches inward. Drought stress is also causing premature coloring and leaf drop on established deciduous trees and shrubs, especially noticeable in native and planted cottonwood. Shedding leaves during drought is a response by plants to conserve water. Limited, early leaf drop should not severely affect established trees with the exception of drought sensitive spe-cies such as red and sugar maple, birch, willow, and mountain ash. Adequate moisture supplied through-out late summer, fall, and winter will reduce twig and branch die-back next spring. If a tree does lose its leaves early, do not assume it is dead. Wait until next spring to determine if it will put on new leaves. Leaf scorch occurs on newly planted trees and shrubs or on established plants with damaged root systems. Scorch is characterized by the appearance of leaves turning brown from the outside margin and moving inward while veins remain green, generally on the side exposed to prevailing wind. During hot, windy weather, the root system is unable to replace the water lost by the leaf canopy. Regular watering and adequate mulch is necessary to keep the root ball moist but not saturated for newly planted trees and shrubs. Injury from drought, and leaf scorch is irreversible. However, long term impact to plant health can be minimized by cultural practices that optimize growing conditions for the roots. A layer of organic mulch, like wood chips or bark, not over 3 inches deep helps reduce moisture loss and will improve water penetration. (continued on top of right column)
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(Continued from bottom of left column
of this section.) Avoid fertilizing trees and shrubs experiencing drought
stress as salts in fertilizers can damage weakened plants. Established trees
and shrubs, especially those in restricted growing space, benefit from a
deep soaking of the root system 12 to 18 inches deep once per month during
the growing season. If dry conditions persist into fall, watering prior
to prolonged cold weather and occasional winter watering during warm sunny
days when soil is dry and unfrozen, can keep shrubs and trees from drying
out.
To water large, established trees and shrubs, remember the majority of water- absorbing roots extend from the edge of the canopy (drip line) outward 2 to 3 times the height of the plant. Water applied next to the trunk or underneath the canopy does little good. Sprinklers are effective at watering large areas of the roots although water may need to be reapplied several different times to soak deeply into the soil and avoid runoff. Soaker hoses can be arranged around the root zone and are effective at slowly applying water to soak deep into the soil. Use a long screwdriver or soil probe to check the depth of moisture. They will slide in easily until dry soil is contacted. Deep root feeders are a very efficient way to water large plants. Use low pressure to work the feeder into the ground and allow water to run 10-15 minutes before moving 5-10 feet and repeating the process. Do not run at full pressure as it can undermine the root system. Work in a spiral pattern out from the canopy edge to cover the root zone. Follow the city ordinance rules when watering. Sprinkling is allowed two days per week, with the day depending on an odd or even address. No more than three hours per day of watering is allowed. Hand watering is allowed anytime, but is not an effective way to deeply soak the root zone of established trees and shrubs except when using a deep root feeder. |
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The current drought has spurred much interest in any product that claims to reduce the amount of water needed to keep lawns and other plants green and growing. One product, Revive, has been on the Colorado scene for many years. What is Revive? In simplest terms, Revive is a wetting agent (a broad term that encompasses a range of surfactant products) combined with an organic compound in the lignosulfonate group. Wetting agents can be useful in turf water management because they reduce the cohesive force of water (the attraction of water for itself - the reason water beads up on a non-absorbent surface), allowing water to more easily penetrate water-repellent soils and thatch. By enhancing both the rate and degree of water penetration, irrigation amount and/or duration may be reduced because of more efficient and uniform penetration. (continued at top of right column) |
(Continued from bottom of left column
of this section.) However, no wetting agent can overcome the effects of a poorly designed irrigation system - dry spots caused by improper head spacing, pressure problems, or malfunctioning heads. Revive was tested in the CSU turf research program in the early 1990s and found to be an effective wetting agent for use on bluegrass with water-repellent thatch. Claims regarding any improvement of soil structure or root zone enhancement were not evaluated by CSU. While often promoted to homeowners by TV/radio garden show personalities, the use of much more than a tablespoon of dishwashing liquid per gallon (of water) as a home-brew wetting agent can cause temporary burning of turf. Dishwashing detergents vary greatly in composition and have not been widely tested for safety on turf. While more expensive than dishwashing liquids, turf-specific wetting agents are preferred for combating water-repellent dry spots on lawns.
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The driest summer in the memory of most Coloradans, combined with very high July and early August heat, has stressed most Colorado lawns. In some communities, where outdoor water use is banned or severely restricted, lawns are completely brown. Lawns that are totally brown may simply be dormant (bluegrass, buffalograss and fine fescue lawns), or they may be severely injured or dead (perennial ryegrass and tall fescue lawns). In communities that allow only the equivalent of 1/2 inch of water per week, it is still advantageous to apply the water to a dormant lawn. This small amount of water will not cause the lawn to green up appreciably, but it will allow crowns, rhizomes, and/or stolons (critical growing points) to maintain a survivable level of hydration. Unfortunately, these small amounts of water will also encourage the growth of weeds already present in the lawn. On those lawns that are still green but stressed, irrigation should be continued as local regulations allow. As much as possible, traffic should be restricted on stressed lawns. Mowing should be done during the coolest times of the day (evening or early morning). When possible, turf in need of irrigation should be irrigated first and mowed the following day. Drought- and heat-stressed turf should not be fertilized, or should be fertilized only with slowly available nitrogen sources. Core cultivation of stressed lawns is not recommended - while this does help water penetrate into root zones, it also has the negative effect of exposing roots to drying. Postpone core cultivation until cooler weather. (continued at top of right column)
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(Continued from bottom of left column
of this section.) Lawn Aeration (Core Cultivation) on Lawns this Fall. Yes or No? 1. If lawns aren't being regularly watered (as is the case in MANY communities), the lawns will likely be so hard that aerification will not be terribly effective. That is, plugs will not likely be pulled from such hard lawns without the benefit of a good soaking rain or a couple of days of intensive irrigation. 2. Lawns that are stressed due to some of the more extreme watering restrictions will not likely benefit from fall aerification (or earlier "beat the fall rush" aerification being promoted by some companies right now). These stressed lawns may actually suffer additional stress (traffic stress from the equipment, increased drying because of open holes). 3. Aerification holes will promote drying of the soil if they do not heal over quickly. On actively growing, regularly watered lawns the holes heal quickly. On stressed, infrequently, irrigated lawns, the holes will stay open longer and thus promote drying of the soil - something we don't need at this point. Plus, drought stressed and (especially) non-irrigated lawns will not produce much in the way of new roots this fall - even if they are aerified. In fact, they may produce MORE roots if left undisturbed (NOT aerified) than if they are aerified. 4. Those lawns that are being watered enough to get good penetration/plug pulling would probably benefit because they are growing "normally" (new roots will form, holes will heal over). Weed control on drought stressed lawns will often be ineffective because the weeds are stressed and do not absorb and translocate herbicides. On stressed lawns, it is important to know what should NOT be done, as much as what should be done.
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September 3,4
Fall Bulbs for Spring
Bloom
September 10, 11
Planting for Fall and
Winter Interest
September 17, 18
Indoor Plantscapes
and Winter
Container Gardening
September24, 25
Xeriscape Maintenance:
A Year in Review
October 1, 2
Seed Starting: Getting
a Jump on Spring
Call Linda (636-8923) to register.
$5 per class or $20 for series of five classes
Aside from the irritation and annoyance that mosquitoes inflict upon humans and livestock alike, the threat of disease pathogen transmission is always present, as the current outbreak of West Nile Virus should remind us. Mosquitoes spread this virus after they feed on infected birds and then bite people, other birds and animals. It is not spread by person-to-person contact and there is no evidence that people can get the virus by handling infected animals. Many birds - especially crows - die from West Nile infection and are an indicator of the presence of the virus.
Mosquito Prevention and Control
Adult mosquitoes prefer to rest on weeds and other vegetation. Homeowners can reduce the number of areas where adult mosquitoes can find shelter by cutting down weeds adjacent to the house foundation and in their yards, and mowing the lawn regularly. Mosquitoes go through their entire life cycle in as little as four days or as long as one month depending on temperature and species characteristics. Under optimum conditions, they go from eggs to larvae in two days. Mosquito larvae develop in standing water. The most effective way to control mosquitoes is to find and eliminate their breeding sites. Homeowners can take the following steps to prevent mosquito breeding on their own property:
By using products with lower concentrations of DEET and by applying as little of the product as needed for your outdoor activities, you can reduce your exposure to DEET. The American Academy of Pediatrics recommends that repellents used on children contain no more than 10% DEET.
DEET products can be applied to clothing, but may damage some synthetic fabrics and plastics, especially products with very high DEET concentrations. Launder treated clothing separately from other clothing. Frequent reapplication or saturation is unnecessary for effectiveness. Use only what is required to maintain protection.
This article excerpted from a Colorado State University Cooperative Extension Fact Sheet.
To view this article in its entirety, please go to web site:
http://www.ext.colostate.edu/westnile/reslist.html
Colorado State University
Cooperative Extension
El Paso County
305 S. Union Blvd.
Colorado Springs, CO 80910
(719) 636-8923