wood chips allegedly affecting street tree health

Garry Brockley · 22nd October 2011, 08:01 AM

Quote:

AN ORANGE horticulturist says Orange City Council is killing its street trees by filling garden borders around the trees with woodchips.
Rod Holcombe said the practice of putting woodchips around street trees was depriving them of the nourishment they needed to shoot in spring.

“There’s a number of street trees around Orange that are under threat and it’s the action of putting in the garden border that has weakened them,” he said.

“If they’re going to put a garden border in they should do it with soil and plant plants around it.

“Filling it with woodchips is a significant negative for the tree because of the root disturbance that comes from it.”

Mr Holcombe said a white cedar tree in Anson Street, near Myer, was one example of a tree whose health was deteriorating because of a garden border filled with woodchips.

He said trees in Kite Street and near the Orange police station were also affected.

“It [the white cedar] is quite an old tree and they’ve hastened its death by doing what they’re doing,” he said.

“The point is, it’s happening all over town.”

Orange City Council city presentation manager Nigel Hobden disagreed, however, that the woodchips had a negative impact on the trees’ health.

“I think you’ll find that the white cedars in Orange aren’t even out in leaf at the moment,” he said.

“From our staff perspective, there’s more benefit having mulch under the trees than there is having bitumen.”

Mr Hobden said putting woodchips around the trees did cause a nitrogen draw down in the soil, but not to the point that it hurt the tree.

“It’s not to the extent that it’s detrimental to the longevity of the trees health and vigour,” he said.

lisa.cox@ruralpress.co

I think this gentleman has been reading the articles on adding mulch into soils before planting new plants as this does have a significant leaching effect on the nitrogen particles, however mulching over the top of established trees is a whole different science.

facts on mulching trees:- In the short term, mulches may decrease nitrogen available for a given crop. A material that has a high carbon content and is very low in nitrogen and other nutrients may actually "bind" or immobilize plant-available nitrogen temporarily. This occurs because soil microorganisms use available nitrogen to metabolize and decay the organic material. The immobilized organic nitrogen can be made available (mineralized) later as the organic matter continues to decompose. (DANA O. PORTER, P.E.)hence why they use rested not green mulch to aleviate this small problem.

when mulching with bark or wood chips, it is best practice to add a nitrogen rich organic fertilizer before adding the bark, but this is not absolute just best practice.

other advantages of mulching trees are it helps reduce soil eradication and can serve as a vapor barrier, thus reducing evaporation of soil moisture. they shade the soil, reducing weed growth and possibly reduces soil temperature increases due to solar radiation.

mulching also is shown to increase healthy micorrhiziae within the soil and has been shown to relieve compaction over time.

Quote:

There may be some positive water quality implications associated with incorporation of mulch materials, provided no significant additional hazardous substances are introduced with the mulches. Organic matter can increase Cation Exchange Capacity (CEC). It also may increase availability of phosphorus in soils (Tisdale and Nelson, 1975). Organic matter and a higher CEC can reduce leaching of some organic and cationic pesticides (Brown, et al., 1983). In some cases, the temporary decrease in nitrogen availability may reduce nitrogen leaching losses below the root zone.

Chipping away at tree health - Local News - News - General - Central Western Daily

Eric Frei · 22nd October 2011, 08:28 AM

From a PDF in this thread by Linda Chalker-Scott along with plenty of other information.

Chunky mulch is best

Quote:

Concern: Wood chip mulches will
tie up nitrogen and cause deficiencies in
plants.
Evidence: Actually, many studies
have demonstrated that woody
mulch materials increase nutrient
levels in soils and/or associated plant
foliage. My hypothesis is that a zone
of nitrogen deficiency exists at the
mulch/soil interface, inhibiting weed seed
germination while having no influence
upon established plant roots below
the soil surface. For this reason, it is
inadvisable to use high C:N mulches in
annual beds or vegetable gardens where
the plants of interest do not have deep,
extensive root systems.

Apocalypsse · 22nd October 2011, 09:56 AM

Quote:

“If they’re going to put a garden border in they should do it with soil and plant plants around it.

“Filling it with woodchips is a significant negative for the tree because of the root disturbance that comes from it.”

This sounds more like they are planting in straight mulch, no soil at all. Where is Orange City anyway?

Eric Frei · 22nd October 2011, 10:01 AM

West of Bathurst

22nd October 2011, 10:01 AM	#4
Eric Frei Admin - Owner Palm & Tree Services in Brisbane Join Date: Jan 2007 Location: Brisbane Posts: 12,996	Re: wood chips allegedly affecting street tree health West of Bathurst __________________ Protect your rights to work - Join Australian Tree Association My businesses:- Qualified Brisbane Palm and Tree Lopping \| Stump Grinding Brisbane \| Brisbane - Gold Coast Consulting Arborist

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