[USCC] Compost and tree planting

[dmhill@aol.com]

Michelle,
I have forwarded your question to the American Nursery and Landscape Association and will post their response as soon as I receive it.

I am a little amazed that, without regard to whether the tree is B&B, bare root or container grown, the urban forestry group categorically does not amend the back fill. As a degreed horticulturist with greater than thirty years of field experience, I have always set the base of a root ball or containerized plant on undisturbed soil in the hole and created a transition zone in the backfill mix, going from the medium in which the tree was gown to the surrounding soil. Soil physics and hydrology do not allow water to pass easily between drastically different soil types. Container grown trees are grown in a very friable, porous medium (often soil less). If this tree gets planted in a hole with no transitional material, very often water collects in the planting pit and does not easily drain to the surrounding soil (called the bath tub effect). Conversely, containerized growing media tends to dry faster than a native soil. When this happens, water does not easily or quickly pass fr
 om a (denser) native soil to a very porous planting mix, so the tree may become dessicated while the surrounding soil has adequate moisture to supply the tree.

The same is true for B&B trees. Field grown trees often have a higher percentage of clay in order for the root balls to maintain integrity. It is extremely rare that the nursery soil and the urban soil will be of the same soil type and/or density, so the physical transition of water is often impeded.

In any case, by improving the water holding capacity, porosity, and supplying nutrient and humates while increasing the populations of beneficial microbes at the root zone, the tree has a better opportunity to flourish earlier after its planting.

With regard to the roots never wanting to leave the nutrient rich planting pit, I have seen this quite often however, it is most often a function of rot-proof (nylon) burlap that was never removed, thus strangling the roots as they mature or containerized plants improperly planted by not cutting circling roots (that become girdling roots) from the container when planted.

Hope this helps. I will post the ANLA response.

David Hill
CycleLogic
(301) 493-5180



-----Original Message-----
From: Young, Michele <Michele.Young at sanjoseca.gov>
To: 'Compost Discussion List' <compost at mailman.cloudnet.com>
Sent: Thu, 27 Mar 2008 4:06 pm
Subject: [USCC] Compost and tree planting










Greetings to all,

In doing a presentation to our local urban forestry group, I was told that
they never recommend putting compost into the backfill hole when planting a
tree. This is because they feel that roots will not search outside of the
root ball area if there is "food" placed there.  I talked to them about
trenching and augering as a way of putting food into other zones, but they
were steadfast about no compost in the planting hole.

All of the planting guides that I have seen and used from the soil
perspective show a compost soil-blend at planting.  I would love to hear
from professionals out there about their experiences, and advice.  Please
check with your urban forestry folks to see if no compost is a common
recommendation, or just a local practice here in San Jose.

Conflicted in San Jose

Turn Over an Old Leaf - Compost!
 
Michele Young  
City of San Jose
Environmental Services Department
200 E. Santa Clara St.   Tower 10
San Jose,  CA  95113
Phone: (408) 975-2519
FAX: (408) 292-6212 

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