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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.”

UCCE orchard and vineyard systems advisor Kari Arnold demonstrates proper tree planting. (Photo: Anne Schellman)

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

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.

A new publication from UC ANR on organic amendments in landscapes is now available for free download from the UC ANR catalog,
While there are some situations where amending poor soil can improve tilth, increase water-holding capacity and add nutrients, by and large most unamended soils allow for adequate plant growth of trees and perennials. Potential problems introduced by amending the soil include nitrogen immobilization, which makes the nutrient unavailable to plants; toxicity from residual chemicals, such as herbicides applied to plant material in the amendment; addition of weeds or root pathogens; damage or destruction of the soil structure; harm to the soil food web; and increased salinity.

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.

Posted on Monday, March 29, 2021 at 10:16 AM
Tags: Ben Faber (6), Jim Downer (5), perennials (1), planting (10), trees (17)
Focus Area Tags: Yard & Garden

Many agricultural issues can be resolved with UC Cooperative Extension

A panel discusses the future of agriculture in California.
There are many issues facing Ventura County farmers that UC Cooperative Extension is working to resolve, according to presentations yesterday at an event celebrating UCCE's first 100 years of science and service. The event was covered by reporter Carol Lawrence of the Ventura County Star.

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.
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.

Posted on Thursday, January 30, 2014 at 11:00 AM

Master Gardeners build low-water demo garden

Over the past year, volunteers in the University of California Cooperative Extension Ventura County Master Gardeners program have transformed space next to the Goebel Senior Adult Center in Thousand Oaks into a living showcase of native, drought-tolerant plants and sustainable garden concepts, said an article in the Ventura County Star.

The "California True Colors Garden and Learning Center" contains a collection of 200  desert plants such as the Palo Verde tree, desert grasses and the violet-flowered foothill penstemon growing along meandering paths and dry pond bed.

"These are tough plants. We don't feed them, we hardly water them, but look how  beautiful they are," said Master Gardener Fayde Macune. "They do well with very little care."

Jim Downer, UC Cooperative Extension advisor in Ventura County, said the garden also has a research component. Forty plants are "Arboretum All-Stars" — specimens provided by UC Davis that are proven to be low maintenance, drought-tolerant and attractive to beneficial wildlife such as pollinating insects. Others will be trial plants.

More information and directions to the garden.


The dry pond (right) at the California True Colors Garden and Learning Center.
The dry pond (right) at the California True Colors Garden and Learning Center.

Posted on Monday, June 18, 2012 at 8:55 AM

Research-based irrigation saves water

The Hansen Research and Extension Center hosted a water workshop this week, touching on a topic that is one of the University of California's top priorities, according to an article in the Ventura County Star.

“We want to make sure the community knows about what Hansen is doing and share some of the research sponsored by Hansen," the story quoted Jose de Soto, the center director.

Sixty to 90 percent of residential water is used outside the home, but typically gardeners irrigate based on estimates of plant water needs, Ventura County farm advisor Jim Downer said.

“They are not research-based,” Downer was quoted in the article. “They are based on what people think will happen.”

Downer said he has established plants in four different climates of California, watering them at varying rates to measure the needed usage.

“We’re not growing crops or looking for yield. If it looks good, there’s no need to water,” Downer said.


Proper irrigation saves water.
Proper irrigation saves water.

Posted on Friday, January 14, 2011 at 9:12 AM
Tags: Hansen (2), irrigation (23), Jim Downer (5), Jose de Soto (1), water (84)

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