Posts Tagged: pruning avocado

Now is NOT the Time to Prune Avocados

When to Prune Avocados and Suggestions of How to Prune

In the past avocados were rarely pruned. In fact, if the trees got very big, growers would stump them down to 3-4 feet and then let them regrow. This would often be a disaster, since the trees rapidly grew to stupendous sizes again. They also might regrow then suddenly collapse, because all that regrowth was coming at the expense of energy being sent to the roots. If the roots were compromised by root rot, they would then not have the energy to fend off the disease. So, by bringing the canopy into balance with a sick root system that was continuing to die and was not being fed by a big canopy, the root death would accelerate and when the canopy and root system became imbalanced again, the whole canopy would collapse, and the tree would die.

Also, this wild regrowth was wild and hard to manage. The adage of “prune avocado trees cautiously” was heard round the avocado community and as a result many growers would not do anything. The trees growing larger and larger and larger with the fruiting canopy going higher and higher and higher and picking costs and liability going up. Tree thinning was practiced, where every other tree would be removed so that light could penetrate into the orchard, encouraging more fruit production and slowing tree growth. But they would still grow, and another thinning would be needed. The original commercial ‘Hass' orchard in Carpinteria started out in 1954 with 140 trees and 40 years later was down to 17 trees and was still productive, but they were monsters that were finally felled by root rot.

Many commercial avocados are now routinely pruned to keep the trees short, so that harvesting costs and other tree maintenance expenses are reduced. Also, more light shines into the trees, so that more fruit is borne on the lower branches. Light or minor pruning can be done any time of year to correct imbalances or limb breakages. However, major or heavy pruning should only be done in the early part of the year from January through April.  Fall or early winter pruning can open up the canopy so that it is more prone to frost damage. The closed canopy holds in the heat better.

The major reason not to prune in fall and early winter is that a perennial, evergreen subtropical like avocado goes into a quiescent stage during the fall in preparation for winter cold. The tree does not go dormant like an apple or peach but goes into a metabolic state that can better handle cold. By pruning in the fall, the tree becomes actively metabolic and more prone to frost damage. The tree needs to slow down to better handle the cold.

Avocados flower and bear fruit at stem terminals, so if you give the tree and buzz cut (heading cuts), all the flower terminals will be cut off and there will be no flowering the following year. It also leads to an explosion of water sprouts that result from bud break up and down the branch because the terminal bud which controls the buds lower down have been removed. Naphthalene acetic acid (Tre-Hold) painted on the cut end can be used to restrict some of this wild bud break.

Whenever possible, thinning cuts should be made, where the branch is removed back to a subtending branch. This results in much less wild growth. Also, when there are buds that start growing into water sprouts, they can be nipped back to force lateral growth. These laterals will then slow down the growth of the sprout and the side terminal buds will also be able to grow and transition of flower buds later.

Work in Carol Lovatt's lab at UCR has shown that terminal buds need a certain maturity to flower and the transition from a vegetative bud to a flowering bud occurs sometime in late summer/early fall. If pruning is done in July, there is not enough time for the new buds to mature by August and there will be no flowers from that branch the following spring. New vegetative buds formed on growth from spring will often have enough maturation time to make the transition to flower buds, resulting in flowering the next spring.

Any major pruning done in later spring and summer is also going to require some protection for the remaining scaffolds from sunburn. Get ready to paint the scaffold with dilute latex paint to protect the once protected bark from sunburn damage. This can pretty rapidly kill the underlying cambium within days if it heats up newly exposed wood.

Again, light pruning can be done at any time of the year, but removing terminals is removing potential fruiting wood. Therefore, if heavy pruning is needed, it is best to remove one branch at a time. To reduce the height of a tree, cut out the tallest branch one year, the next tallest branch the following year, and so on until the tree is down to the height required. The process may take three to four years. By reducing the height over several years, the tree is put under less stress, less disease is likely to occur and fruit production is not drastically reduced. Pruning the sides of the tree should be done in the same way. Prune off a side branch that most impinges on a neighboring tree one year, then the next worst offender in the second year, and over the years continue this process until there is light all around the tree.

If pruning creates major open areas in the tree to sunlight where there once was shade, the exposed branches should be painted with white latex paint diluted with water so that it can be sprayed on. It needs to be white enough that it can reflect sunlight and avoid heat damage that can cause sunburn. Sunburn can utterly destroy all the work that has been done.

If the trees are really monsters, the only real alternative is to bring the whole tree down. But not stumping, rather scaffolding where much of the structure is maintained. This is where the tree is brought down to as high a height as is convenient and safe. By cutting the tree to a height of 8 feet or so, there is not so much rank regrowth because a greater portion of the tree is retained. Also, many times there are leafy branches that remain that will flower and fruit and slow the wild regrowth. Water sprouts that form should be headed back to force lateral growth that encourages stems that will flower, which will also slow the wild regrowth.

And one last warning. Do not. Do not. Do not. Got it? Prune sick trees. If the roots are compromised, the regrowth is going to be hard on the roots. Get the trees perked up with one of the phosphite products so that they are ready to go through this process. You may have to wait a couple years to start the pruning process until the trees are in shape for the rigors.

In summary: Late winter to early spring is the sweet spot for pruning your avocado trees. This timing is key because it sidesteps the risk of cold damage and aligns with the tree's natural flowering cycle. Pruning too late can lead to sunburned branches and a reduced fruit set the following year.

 

Image:  Don't make cuts like this. Those stubs or going to create a royal mess of new, wild growth.

avocado pruning stub 1

Lawn-pocalypse! Surviving Drought

Ah, summer! The season of sunburns, pool parties, and… lawn droughts. If your once lush, green carpet now looks like a crunchy brown doormat, you're not alone. Let's dive into why your yard is staging a dramatic death scene and what you can do to...

Bermuda grass and weeds overtaking drought stressed turf grass.

A patch of former lawn, mostly dead, with a few green weeds and Bermudagrass

Climate-Change Resources

University of California UC ANR Green Blog (Climate Change and Other Topics) https://ucanr.edu/blogs/Green/index.cfm?tagname=climate%20change (full index)

Examples:

     -  Save Trees First: Tips to Keep Them Alive Under Drought https://ucanr.edu/b/~CdD 

     - Landscaping with Fire Exposure in Mind: https://ucanr.edu/b/~G4D

     - Cities in California Inland Areas Must Make Street Tree Changes to adapt to Future Climate  https://ucanr.edu/b/~oF7

Drought, Climate Change and California Water Management Ted Grantham, UC Cooperative Extension specialist (23 minutes) https://youtu.be/dlimj75Wn9Q

Climate Variability and Change: Trends and Impacts on CA Agriculture Tapan Pathak, UC Cooperative Extension specialist (24 minutes) https://youtu.be/bIHI0yqqQJc

California Institute for Water Resources (links to blogs, talks, podcasts, water experts, etc.) https://ciwr.ucanr.edu/California_Drought_Expertise/

UC ANR Wildfire Resources (publications, videos, etc.) https://ucanr.edu/News/For_the_media/Press_kits/Wildfire/ (main website)

      -UC ANR Fire Resources and Information https://ucanr.edu/sites/fire/ (main website)

            -Preparing Home Landscaping https://ucanr.edu/sites/fire/Prepare/Landscaping/

UC ANR Free Publications https://anrcatalog.ucanr.edu/ (main website)

- Benefits of Plants to Humans and Urban Ecosystems: https://anrcatalog.ucanr.edu/pdf/8726.pdf

 -Keeping Plants Alive Under Drought and Water Restrictions (English version) https://anrcatalog.ucanr.edu/pdf/8553.pdf

  (Spanish version) https://anrcatalog.ucanr.edu/pdf/8628.pdf

-  Use of Graywater in Urban Landscapes https://anrcatalog.ucanr.edu/pdf/8536.pdf

-  Sustainable Landscaping in California https://anrcatalog.ucanr.edu/pdf/8504.pdf

 

Other (Non-UC) Climate Change Resources

Urban Forests and Climate Change. Urban forests play an important role in climate change mitigation and adaptation. Active stewardship of a community's forestry assets can strengthen local resilience to climate change while creating more sustainable and desirable places to live. https://www.fs.usda.gov/ccrc/topics/urban-forests

Examining the Viability of Planting Trees to Mitigate Climate Change (plausible at the forest level) https://climate.nasa.gov/news/2927/examining-the-viability-of-planting-trees-to-help-mitigate-climate-change/

Reports and other information resources coordinated under the auspices of the United Nations and produced through the collaboration of thousands of international scientists to provide a clear and up to date view of the current state of scientific knowledge relevant to climate change. United Nations Climate Action

Scientific reports, programs, action movements and events related to climate change. National Center for Atmospheric Research (National Science Foundation)

Find useful reports, program information and other documents resulting from federally funded research and development into the behavior of the atmosphere and related physical, biological and social systems. Search and find climate data from prehistory through to an hour ago in the world's largest climate data archive. (Formerly the "Climatic Data Center") National Centers for Environmental Information (NOAA)

Think tank providing information, analysis, policy and solution development for addressing climate change and energy issues (formerly known as the: "Pew Center on Global Climate Change"). Center for Climate & Energy Solutions (C2ES)

Mapping Resilience: A Blueprint for Thriving in the Face of Climate Disaster. The Climate Adaptation Knowledge Exchange (CAKE) was launched in July 2010 and is managed by EcoAdapt, a non-profit with a singular mission: to create a robust future in the face of climate change by bringing together diverse players to reshape planning and management in response to rapid climate change. https://www.cakex.org/documents/mapping-resilience-blueprint-thriving-face-climate-disaster

Cal-Adapt provides a way to explore peer-reviewed data that portrays how climate change might affect California at the state and local level. We make this data available through downloads, visualizations, and the Cal-Adapt API for your research, outreach, and adaptation planning needs. Cal-Adapt is a collaboration between state agency funding programs, university and private sector researchers https://cal-adapt.org/

Find reports, maps, data and other resources produced through a confederation of the research arms of 13 Federal departments and agencies that carry out research and develop and maintain capabilities that support the Nation's response to global change. Global Change (U.S. Global Change Research Program)

The Pacific Institute is a global water think tank that combines science-based thought leadership with active outreach to influence local, national, and international efforts to develop sustainable water policies. https://pacinst.org/our-approach/

Making equity real in climate adaptation and community resilience policies and programs: a guidebook. https://greenlining.org/publications/2019/making-equity-real-in-climate-adaption-and-community-resilience-policies-and-programs-a-guidebook/ 

Quarterly CA Climate Updates and CA Drought Monitor Maps (updated each Thursday) https://www.drought.gov/documents/quarterly-climate-impacts-and-outlook-western-region-june-2022

 

 

 

 

Drought focus of Water Resources IMPACT magazine special issue

UC ANR experts address emotional toll of drought

Preparing the American West for prolonged drought is the focus of a double issue of Water Resources IMPACT magazine. The California Water Commission staff are guest editors for this special open-access edition of the magazine, which is published by the American Water Resources Association.   

Faith Kearns, academic coordinator of University of California Agriculture and Natural Resources' California Institute for Water Resources, is among the authors delving into how drought impacts people and the environment and how we can better prepare for the inevitable. 

The first issue, published on Feb. 14, focuses on water scarcity issues confronting California and the ways these issues affect different sectors. 

In “Trauma, Care, and Solidarity: Addressing the Emotional Toll of Chronic Drought,” Kearns highlights the effects of drought on mental health. She points to the spike in suicide hotline calls when wells ran dry in Southeast Asian communities in California's Central Valley.

By listening to Southeast Asian farmers, Ruth Dahlquist-Willard and Michael Yang of UC Cooperative Extension were able to “lighten the load” for them by providing pragmatic support, Kearns writes.

“The scale of some of these highly emotional issues – drought, wildfires, climate change – can make them seem incredibly difficult, if not impossible, to deal with,” Kearns said. “At the same time, they are affecting everyone living in the western U.S. on a daily basis. I wanted to highlight and provide models based on work that people – whether they are researchers, clinical psychologists, or Cooperative Extension advisors – are doing right now to ease the way.”

The authors who contributed to the double issue are a diverse array of Tribal experts, academics, nongovernmental organization thought-leaders, water managers and water policy influencers, each of whom brings their own perspective on the topic of drought. Their expertise and perspectives in climate science, water policy and water management will help inform drought-related decision-making and support policies that better prepare the state to thrive during periods of prolonged water scarcity.

In addition to Kearns, the first issue includes articles contributed by:

• Samantha Stevenson, University of California, Santa Barbara
• Jay Lund, University of California, Davis
• Ron Goode, North Fork Mono Tribe
• Andy Fecko, Placer County Water Agency
• Jeff Mount, Public Policy Institute of California, and Ted Grantham, University of California, Berkeley/UC Cooperative Extension
• Nat Seavy and Karyn Stockdale, National Audubon Society
• Kjia Rivers, Community Water Center
• Cannon Michael, Bowles Farming
• Michelle Reimers, Turlock Irrigation District

The January/February edition of Water Resources IMPACT magazine can be accessed, free of charge, on the American Water Resources Association website at https://www.awra.org under “Publications.”

The second issue, to be published in March, will focus on drought response, considering the options for adaptation. This two-part series complements the Commission's work on strategies to protect communities and fish and wildlife in the event of a long-term drought.

 

 

Your water-efficient landscape doesn’t have to be barren

UC climate-ready landscape trials identify low-water yet attractive plants

Good news: roses can be a part of your water-efficient landscape. Lorence Oki, UC Cooperative Extension environmental horticulture specialist in the UC Davis Department of Plant Sciences, identified rose cultivars that remain aesthetically pleasing with little water.  

Oki is the principal investigator of the Climate-Ready Landscape Plants project, which may be the largest irrigation trial in the western U.S., and the UC Plant Landscape Irrigation Trials (UCLPIT), the California component of that project. These projects evaluate landscape plants under varying irrigation levels to determine their optimal performance in regions requiring supplemental summer water.

“There are some assumptions that pretty plants use a lot of water, like roses,” Oki said. “Everyone thinks they need a lot of water, but we've found some that don't, and they still look great. A water-efficient landscape doesn't need to look like a Central Valley oak-grassland in the summer. It can look really attractive.”

In 2021, Oki's team at UC Davis identified Lomandra confertifolia ssp. pallida "Pom Pom" Shorty and Rosa "Sprogreatpink" Brick House® Pink as two of the best low-water plants in the trial. 

“The useful tip or information that is shared at the end of each trial is the selection and designation of plants as Blue Ribbon winners. These are the plants that looked good with an overall rating of 4 or higher throughout and were on the low (20%) water treatment,” said Natalie Levy, associate specialist for water resources, who manages the project at the UC ANR South Coast Research and Extension Center.

How plants earn a blue ribbon

Each trial year, the selection of new plants is based on research recommendations and donated submissions from the nursery industry. The landscape plants are trialed in full sun or 50% shade cover.

Irrigation treatments are based on the rate of evaporation and plant transpiration (evapotranspiration) measured through a local California Irrigation Management Information System (CIMIS) weather station that provides a reference evapotranspiration (ETo) rate.

Three levels of irrigation are provided to the plants equal to 20%, 50%, and 80% of ETo. The volume of water applied is the same at each irrigation based on soil characteristics, but the interval between applications varies with weather and the treatment. Using this method, irrigations for the 20% treatment are less frequent than the 80% treatment.

“The 20% treatment during the 2022 trial was irrigated an average of once per month while the 80% treatment was irrigated weekly,” explained Levy.

During the deficit irrigation trial, monthly height and width measurements are taken to determine the plant growth index. Monthly qualitative aesthetic ratings on a scale of 1 to 5 are determined for foliage appearance, flowering abundance, pest tolerance, disease resistance, vigor and overall appearance.

A second round of flowering abundance and overall appearance measurements are also taken to capture more of the blooming period. For example, UCLPIT identified in the 2020 trial at South Coast REC that the "Apricot Drift" rose had a mean overall appearance score of 3.5 out of 5, deeming it “acceptable to very nice” and a low water use plant within the Water Use Classification of Landscape Species or WUCOLS guide.

Project expands options for landscape planting

While attending UC Davis as a master's student, Karrie Reid, retired UCCE environmental horticulture advisor for San Joaquin County, assisted Oki with landscape water conservation research. The landscape plant irrigation assessments were initiated at UC Davis in 2004 and the UCLPIT project, now in its 20^th year, originated from her master's thesis project from 2005 to 2007. A CDFA grant supported duplicating these fields at the South Coast REC in 2017.

“(WUCOLS) only has 3,500 plants in it. There are guesses that there are close to 10,000 cultivars in urban landscapes in California, if not more,” said Oki. “WUCOLS also didn't have numerical ratings. Instead, you'll see verbal ratings like ‘low water use' or ‘high water use.'”

The UCLPIT project has not only developed numerical recommendations for irrigation, but it has also added new landscape plants that are compliant with California's Model Water Efficient Landscape Ordinance. In fact, UCLPIT's data is one of the few sources that can be used to supplement WUCOLS.

Geographic diversity of trial sites adds to knowledge base

In addition to UC Davis and South Coast REC in Irvine, the trials have expanded beyond California as the Climate-Ready Landscape Plants project and is in progress at Oregon State University, University of Washington, University of Arizona and Utah State University thanks to a USDA/CDFA grant awarded in 2020.

Lloyd Nackley, associate professor of nursery production and greenhouse management at Oregon State University, is the principal investigator of the trial in the Portland metro area, which is entering its third year.

“People know that there are drought tolerant plants, but there are many. We're trying to highlight lesser known or newer varieties. And even though the trial is three years, most gardeners would hope that their garden lasts longer than that,” said Nackley.

One of the observations that Nackley recalls is of the Hibiscus Purple Pillar plant. Unlike the trial at South Coast, the Purple Pillar did not perform well in Oregon in the spring.

“It wasn't until August that we saw the plant bloom and begin to look like what we saw from South Coast in April,” Nackley said.

Ursula Schuch, horticulture professor and principal investigator of the trial taking place at the University of Arizona, was also surprised at the range of performance among different plant types and the effects of irrigation, heat and temperature.

“This research will reassure green industry professionals that they can stretch their water budget to successfully cultivate more plants, watering them according to their needs instead of irrigating every plant according to the highest water-using plants,” said Schuch.

Although research is only conducted in the West, the hope is that there will be trials in other regions of U.S.

Doing so would yield comprehensive information about the plants and their performance in different climates. As extreme weather events persist in the U.S., disease pressure and risks do too. Trials throughout the country would provide location-specific data regarding disease susceptibility. 

To learn more about the UCLPIT research project, visit https://ucanr.edu/sites/UCLPIT/

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