Posts Tagged: Jim Downer
No need to amend soil when planting new trees or perennials
Gardeners who follow conventional wisdom and nursery recommendations to mix organic amendments into the soil when planting new trees or perennials in their landscapes are making a mistake, according to UC Cooperative Extension environmental horticulture experts.
“This is one of the garden myths that I'm trying to dispel,” said Jim Downer, UCCE environmental horticulture advisor in Ventura County. “We recommend residents not amend the soil when they are planting based on outcomes we have observed in research.”
Downer and Ben Faber, UCCE advisor for water, soils and subtropical crops in Ventura County, summarized this and other information about the use of organic amendments in home landscapes in a six-page publication now available for free download from the UC Agriculture and Natural Resources catalog at https://anrcatalog.ucanr.edu/Details.aspx?itemNo=8711.
The publication says research has not shown that adding amendments to planting holes for perennial plants provides a significant advantage compared to using native backfill.
With perennial plants, the roots do not stay in the planting hole for long, so amendments would only be effective for a short time. The practice of amending the soil further harms the plant by creating an interface where the soil in the planting hole is different from the native soil.
“When that happens, roots and water don't move as well through the soil,” he said.
While there are few reasons to mix organic amendments into the soil, Downer said mulching the soil surface with uncomposted organic matter is almost always beneficial.
“If your goal is to get organic matter into the soil, we recommended topping the soil with fresh, undecomposed wood chips. It will give you microbial stimulation and suppress disease. Arthropods will slowly grab pieces of the mulch and incorporate it into the soil at a gentle rate,” he said.
The publication also provides information about various common organic amendments – such as coconut fiber, coffee grounds, horse manure, peat moss and green waste compost – with details about each product's benefits and detriments.
UC study seeks street trees that can cope with climate change
Reposted from UCANR News
The changing climate predicted for California – including less rain and higher day and nighttime temperatures – is expected to cause chronic stress on many street tree species that have shaded and beautified urban areas for decades.
Realizing that popular trees may not thrive under the changing conditions, UC Cooperative Extension scientists are partnering with the U.S. Forest Service in an unprecedented 20-year research study to expand the palette of drought-adapted, climate-ready trees for several of the state's climate zones.
“The idea is to look at available but under-planted, drought-tolerant, structurally sound, pest resistant trees for Southern California that do well in even warmer climates,” said Janet Hartin, UCCE horticulture advisor in San Bernardino County.
Hartin, a 34-year veteran advisor, said the project is her first to stretch to 20 years; it will likely extend past her tenure with UCCE.
“I'd like to retire in five or six years,” she said. “But I'm very excited about being a pioneer in a study that will continue with my successors. I think it's important for our children and our children's children, as well as for the environment.”
At the end of 2019, with three years of data on tree health and growth rates, the scientists expect to be able to publish the first results and make them available to arborists, urban foresters and residents throughout the regions of the study.
Twelve tree species were selected for each climate zone in the comparative study, with several area parks used as control sites. Hartin and her Southern California research collaborators – UCCE advisors Darren Haver of Orange County and Jim Downer of Ventura County – worked closely with UC Davis plant biologist Alison Berry, UC Davis research associate Greg McPherson and USFS research urban ecologist Natalie van Doorn to select promising species.
They looked for trees that are already available at local nurseries, but are underutilized. The trees in the project exhibit drought tolerance and disease resistance, plus produce minimal litter. The researchers also sought trees that would provide ample cooling shade for a long time – ideally 50 years or longer.
The varieties come from areas around the world with climates similar to California. Two trees planted in replicated plots at the UC Riverside Citrus Field Station are native to Australia, two are native to Oklahoma and Texas, one is native to Asia and two are non-native crosses of other trees. Three of the trees are native to California: the netleaf hackberry, Catalina cherry and island oak.
“Trees are a long-term investment,” Hartin said. “A tree will live 50, 70, 90 years. The proper selection is very important to help ensure longevity.”
Making the long-term investment with the proper selection yields considerable returns. In a warming world, trees are natural air conditioners.
“Urban areas create heat islands, with dark asphalt surfaces reradiating heat. Cities can be 10 to 20 degrees warmer than the surrounding environment,” Hartin said.
Other tree benefits include soil health and stability, wildlife habitat and aesthetic beauty.
Following are a sampling of trees that are part of the comparative study:
Acacia – A 20-foot-tall, 20-foot wide evergreen that is drought resistant, and withstands moderate irrigation. Native of Australia.
Blue palo verde – A tree that reaches about 25 feet in height, the Blue palo verde is drought resistance and lives 50 to 150 years. Its trunk, branches and leaves have a blue-green hue. Native to the southwestern U.S. and Mexico.
Brazilian cedarwood – A native of Brazil and Paraguay, the deciduous tree grows to 50 to 65 feet. The tree produces pale yellow tubular flowers in the spring.
Catalina cherry – Native to the chaparral areas of coastal California, the Catalina cherry grows to 30 feet high. The evergreen tree tolerates drought when mature. It produces sweet purple-to-black edible fruit.
Chinese pistache – A deciduous tree with beautiful fall color. Grows to 35 feet tall, 30 feet wide. Drought resistant, but tolerates moist soil. Native to central and western China.
Desert willow – Growing to 30 feet tall and living 40 to 150 years, the desert willow tolerates highly alkaline soil and some salinity. A deciduous tree, it boasts large pink flowers all summer that attract hummingbirds and other wildlife. Native to the southwestern U.S. and northern Mexico.
Escarpment live oak – Native to west Texas, this tree is cold hardy and drought tolerant. Typically evergreen, it can be deciduous in colder climates.
Ghost gum – Very tall at maturity and drought tolerant. An Australia native.
Indian laurel – Commonly called a ficus, this is a 35-foot-tall, 35-foot-wide tree at maturity that is drought resistant and tolerates highly alkaline and saline soils. Shade potential is high. Native of Asia and Hawaii.
Ironwood – A southwestern and northern Mexico native, Ironwood is semi-drought resistant once mature and tolerates alkaline soil. Ironwood, which grows to about 33 feet tall, can live 50 to 150 years.
Island oak – This tree is native to five of six California off-shore islands. Drought tolerant, it grows to nearly 70 feet tall when mature.
Maverick mesquite – Native to the southwestern U.S. and northern Mexico, this tree does well in full sun and is drought resistant once established. The tree grows to 35 feet tall. The Maverick mesquite is a thornless variety.
Mulga – A versatile and hardy tree that grows 15 to 20 feet in height, the mulga – a Western Australia native – tolerates hot and dry conditions. The leaves are evergreen and the tree has yellow elongated fluffy flowers in spring.
Netleaf hackberry – A California native, the netleaf hackberry grows to 30 feet. Its deep root systems and heat resistance makes the tree idea for urban conditions.
Rosewood – Native to southern Iran, Indian rosewood grows to 65 feet tall, and 40 feet wide. Evergreen. Semi drought resistant and intolerant of alkaline soil.
Shoestring Acacia – Evergreen and 30 feet tall when mature, shoestring acacia is drought resistant and thrives in slightly acidic to highly alkaline soils. Native to Australia.
Tecate cypress – A native of Southern California and Mexico, the Tecate cypress is very drought tolerant. Its foliage is bright green. Young trees are pyramidal in shape, becoming more rounded or contorted with age.
Partners in the tree study are Los Angeles Beautification Team volunteers, LA Parks and Recreation team, Chino Basin Water Conservation District, and Mountain States Wholesale Nursery.
Funding and other support is provided by LA Center for Urban Natural Resources Sustainability, ISA Western Chapter, Britton Fund, USFS Pacific Southwest Research Station, and the UC system.
Entomological Association of Southern California Quarterly Meeting
The Entomology Association of Southern California will be holding a quarterly meeting at the Los Angeles Arboretum. These meetings address a variety of entomological related subjects relevant to local and state pest issues and are a great way to meet and share information with other individuals who are interested in this area of science.
Presentations on:
- Bark beetle-caused tree mortality and risk following various management regimes in south California.
- Polyphagous Shot Hole Borer/Fusarium dieback: Recognizing symptoms and removing hosts.
- Observations on the control of bark boring and other wood boring beetles in landscape trees.
- Polyphagous Shot Hole Borer - a voracious Ambrosia Beetle threatening California's crops and native plants.
- Environmental effects on Polyphagous Shot Hole Borer.
- Influence of air pollution on bark beetle outbreaks.
This association has an annual membership fee of $45. Memberships cover annual registration for all four quarterly meetings in December, March, June and September.
If you are interested in attending:
Date: September 9, 2014
Time: 9:00 am - 4:00 am
Location:
Los Angeles Arboretum
301 North Baldwin Ave.
Arcadia, CA
Contact: Dr. Jim Downer, 805-645-1458 or ajdowner@ucanr.edu
Entomology Association of Southern California Spring Meeting
The Entomology Association of Southern California will be holding a quarterly meeting at the Los Angeles Arboretum. These meetings address a variety of entomological related subjects relevant to local and state pest issues and are a great way to meet and share information with other individuals who are interested in this area of science.
Presentations for this meeting will cover:
- California's invasive slugs, future threats & some novel approaches for their control
- Asian Citrus Psyllid research at California Polytechnic University
- County Reports
- Natural history and IPM practices for use against an atypical stink bug, the Bagrada bug
- GIS database of land gastropods of California - native and not
This association has an annual membership fee of $45. Memberships cover annual registration for all four quarterly meetings in December, March, June and September.
If you are interested in attending:
Date: March 4, 2014
Time: 8:15 am - 3:00 am (presentations start at 9:00 am
Location:
Los Angeles Arboretum
301 North Baldwin Ave.
Arcadia, CA
Contact: Dr. Jim Downer, 805-645-1458 or ajdowner@ucanr.edu
See here for the agenda.
Many agricultural issues can be resolved with UC Cooperative Extension
At the event, UCCE advisors talked about the status of ag industry in Ventura County, where total farm production is nearly $2 billion annually. Strawberries, the county's leading crop since the early 2000s, are valued at $690 million. However, production is threatened by dwindling water supplies.
"We can't avoid this topic," said Oleg Daugovish, UCCE advisor.
UCCE advisor Ben Faber also discussed the water situation. The average annual rainfall in Oxnard was 17 inches between 2003 and 2008.
"We're living in an environment that rarely sees the average rainfall," Faber said.
Faber's work includes showing growers how using too much or too little water is more likely to cause plant disease and demonstrating new ways of measuring the water content in soil, the article said. One solution to water woes is using recycled water in nurseries. The practice saves 14 to 42 percent of water.
UCCE advisor Jim Downer talked about the movement of exotic pests that are a potential challenge to agriculture. California is particularly vulnerable to these pests because of its vast and varying geography and climate, he said.
Ventura County's top 10 ag commodities were on dispaly in a Model T truck at the UC Cooperative Extension Celebration of Science and Service.