Monday, December 28, 2015

Mistletoe: An Enemy to Plants

Because they have the unique ability to take energy directly from another plant, the various species of mistletoe can cause the slow, steady decline of host trees and shrubs.

Mistletoes are perennial, shrubby, woody or semi-woody flowering plants that attach themselves to other plants and steal water and nutrients from the host plant.  Because they are dependent upon these host plants for nourishment, they are called parasites.  Unlike dodder, which lacks any ability to produce food for itself, the mistletoes do contain the green pigment chlorophyll that allows them to manufacture food from the energy of the sun. 

In the desert Southwest, there are about a dozen different species of mistletoe that affect trees and shrubs.  Each of these species have the ability to invade the living tissue of host plants and extract water and nutrients for their own growth and development.  It is this unceasing loss of strength, coupled with the twisting and distortion of branches caused by the mistletoe that can eventually lead to the decline and sometimes death of trees and shrubs.

The traditional European mistletoe is Viscum album, but in the United States two genera, Arceuthobium and Phoradendron are the representatives of the family.  Arceuthobium species are dwarf mistletoes and are weak, herbaceous plants with leafless yellow-green to orange stems.  These mistletoes parasitize pines and junipers all across the Southwest.

Members of the Phoradendron generally have well-developed leaves on strong, shrubby, almost woody stems.  Some species have large, yellow-green leaves while other species are essentially leafless.  The common desert mistletoe that infests many of the desert legume trees like palo verde, mesquite, and ironwood has only scale-like leaves.  The large-leafed yellow mistletoe is often picked and sold during the holiday season as a way to steal a kiss from someone special.  It is most commonly found on riparian softwood trees like cottonwood, sycamore, willow and ash.

Most mistletoe species produce small white to pinkish or green-tinged berries, whose single hard seeds are surrounded by fleshy, sticky pulp.  The fruit seems irresistible to birds, who then redistribute the seeds to new locations, not only through their droppings, but also by inadvertently carrying the sticky seeds on their beaks and feet.

While otherwise healthy host plants may seem to tolerate one or two mistletoe plants, the parasitic plant’s ability to effectively produce and disperse seeds all but insures the spread of the infestation and the slow decline and even death of the host plant.  The weakening, disfigurement and eventual death of shade, food and lumber producing trees represents a significant worldwide economic loss each year.

Control of parasitic plants is often difficult.  The easiest and most common method of control is to simply prune or break off the plants.  This is best done before flowering to prevent the development and dispersal of seeds.  Removal of the parasites also helps to reduce the drain on the host tree as pruning prevents the loss of valuable water and nutrients from the host. 

Unfortunately, mistletoe pruned in this manner usually does not remove all of the parasitic plant, and the parasite will often grow back quickly.  For this reason, frequent pruning is often necessary.  To prevent frequent regrowth, remove the mistletoe as close to its point of attachment as possible.  Some bark tissue may safely be removed during this process, but try not to cut too deeply, or the branch may snap under its own weight or in a wind.

A more permanent step would be to completely prune away infected limbs and branches up to 12 or more inches below the mistletoe point of attachment. This type of pruning works well for younger clumps of mistletoe, but it cannot be done on older growth mistletoe, or where the mistletoe is on large, often essential limbs.  Be sure to prune the infected limbs back to their point of attachment with a larger branch or the trunk.  Never leave the stub end of a branch that could invite the entry of other diseases and wood-destroying insects.

Where infestations occur on essential branches or on the trunks of trees, some measure of control can be achieved by pruning the offending mistletoe back flush with the tree and then wrapping the exposed points of attachment with dark, light-excluding plastic sheeting.  The lack of light on the remaining parasite tissue will prevent the regrowth of the pest.  As the mistletoe is deprived of sunlight, the parasite will eventually die.  However, this make take a year or two, so it is important to check the plastic wrap regularly and replace it if it begins to degrade.

Mistletoe is a common pest on local landscape trees, but by careful vigilance and proper tree care much of the damage to, and death of, these valuable plants can be avoided.

If you have questions, you can reach one of the Master Gardeners at the Cooperative Extension office, 820 E. Cottonwood Lane, Building C, in Casa Grande.  The telephone is (520) 836-5221, extension 204.

The University of Arizona is an equal opportunity, affirmative action institution.  The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities.

Rick Gibson
Extension Agent, Agriculture
University of Arizona Cooperative Extension
820 E. Cottonwood Lane, Building C
Casa Grande, Arizona 85222
Voice:  (520) 836-5221
Fax:     (520) 836-1750
email:   gibsonrd@ag.arizona.edu

Date: November 26, 2014

Wednesday, December 16, 2015

Plants Provide Many Benefits In Our Lives

In a hurry up world where life seems to constantly accelerate and the day-to-day challenges appear to bring ever more stress, plants can impart a sense of needed stability and well-being in our lives. 

There are many scientific studies that indicate a strong relationship between healthy people and exposure to plants, both indoor and out.  Here are some examples taken from a series of articles published just in the January-March 2000 edition of  “HortTechnology”, a quarterly journal for horticultural professionals.

The first example comes from one of the earliest studies looking at the beneficial effects of plants.  Patients having a room with a view of trees rather than a view of a brick wall spent almost a day less in the hospital, used fewer doses of strong pain relievers, and received fewer negative comments from hospital staff on their charts.  The study instantly attracted the attention of both the medical community and horticultural researchers.  

In another study, people in an experiment viewed slides of nature scenes with water and vegetation, slides of nature scenes with only vegetation, or slides of urban scenes without vegetation.  When people viewed either of the nature scenes, they exhibited higher alpha brain wave amplitudes than when viewing urban scenes.  

“Okay, Rick, what exactly does that mean?”  Higher alpha brain wave amplitudes are generally associated with lower levels of physiological arousal and higher levels of attentive relaxation.  In other words, those tested were judged to be under less stress.  That is a good thing.  The subjects also reported that the nature slides held their attention better than the urban slides, even though all of the slides were judged to have similar informational content. 
            
One study focusing on college students showed that those performing tasks that required deep mental concentration performed significantly better on some tests when they enjoyed a window room that opened out onto a nature scene than those who had views of scenes dominated by buildings and sidewalks.  Nature scenes seemed to enhance mental attention and reduce fatigue.

A 1996 study asked apartment complex residents about domestic violence.  Respondents lived in public housing and could not choose their apartments.  Some were assigned to live in complexes surrounded by trees, while others were assigned to buildings without green surroundings.  When asked if they had engaged in violence during the past year, 22% of the women interviewed from the apartments without trees said “yes” while only 13% of the women in the apartments surrounded by trees said “yes”.  When asked if they had hit their children in the past year, 14% from the non-green apartments said “yes”, while only 3% living in apartments near trees said “yes”.   

The list of studies goes on and on, here in the U.S., and around the world.  The evidence is quite clear.  Scenes associated with plants can reduce stress, speed healing, enhance workplace productivity and improve the human outlook on life.   

These results have not gone unnoticed.  Around the world, plants are showing up inside public buildings, in malls, in hospitals, and long term care centers.  School gardens are being planted and cared for.  Community gardens, consumer supported agriculture enterprises, and agricultural tourism operations are flourishing.  Adults working in the court systems assign juvenile offenders to work in community gardens.  Yes, horticultural therapy has become a viable tool in the medical field, but it is also key to well being in our every day lives.  

These real benefits, however, are sometimes masked, covered up, if you will, by the very challenges of life that make our involvement with plants so essential.  The bottom line is that we are becoming too busy to garden, to care for house plants and to plant trees and shrubs.  

If we do install landscapes, we often give in to the temptation to make them so labor-free that we do not find the need to interact with them in any way other than in the most brief of encounters.  This may be helpful in our busy worlds, but it is expensive in terms of the very real benefits that could be ours if we regularly went out among our plants.

So, what can you and I do?  There are several ways to enhance our interaction with plants and to improve the surroundings in which we live.

First, bring plants indoors.  Look around the interior living space and search for locations where an indoor plant might fit.  Identify  locations where light, humidity, and temperature conditions fit the needs of the plant.   For example, do not place a boston fern in an area where the cooler or heater vents would blow on the plant and dry it out.  Ferns like moist, humid areas such as in the shower or bath.  

Group indoor plants into natural appearing arrangements that give a sense of the outdoors from which they came.  Such arrangements help create a peaceful, natural feeling similar to that experienced in native environments.

Second, search for ways to make outdoor landscapes user friendly.  Arrange and install outdoor landscapes with the intent that they will encourage human interaction.  Select plants that fit the specific needs of the landscape and of the people that will use it.  Let the landscape be an extension of the home so that it will be an easy and natural step to exit the home and immerse oneself in the outdoors.  A well designed and maintained landscape will entice people indoors to move outside.

Consider placing benches or chairs in strategic locations that invite a passerby to linger and enjoy the setting.  This may be tucked away between trees or behind shrubs away from busy traffic areas, or it may simply be next to favorite flowering shrubs or garden areas.  Such locations encourage introspection and relaxation from busy schedules.

Third, notice the use of plants and natural environments in public places and recognize them for what they bring to those who visit those areas.  Many malls, for example, spend considerable resources to bring the natural environment inside for a peaceful, if not restful, shopping experience.  Encourage businesses and other establishments that you frequent to consider installing plants into their decor.  Tell them about the potential benefits that could come both to them and their customers from the practice.

Fourth, become active in neighborhood and community beautification committees, school garden projects and community garden efforts and encourage the proper use of landscapes and indoor plants in all areas.  Volunteer time not only lifts those served, but also reaps benefits to those serving.

Finally, become informed about plants and the potential benefits that come from human interaction with plants.  Know how to properly select, install and care for indoor and outdoor plants in our harsh, desert environment.  

Healthy plants in our living environment can help all of us accrue actual emotional, physical and psychological benefits each and every day.  The bottom line is, plants help us live better lives. 

If you have questions, you can reach one of the Master Gardeners at the Cooperative Extension office, 820 E. Cottonwood Lane, Building C, in Casa Grande.  The telephone is (520) 836-5221, extension 204. 

The University of Arizona is an equal opportunity, affirmative action institution.  The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities.


-- 
Richard Gibson
Extension Agent, Agriculture
University of Arizona
Pinal County Cooperative Extension Office
College of Agriculture and Life Sciences

820 E Cottonwood Ln, #C
Casa Grande, AZ 85122
Tel: (520) 836-5221 ext. 227
Fax: (520) 836-1750