Sunday, May 19, 2013

Protect the Zone

There are many standards for tree protection zones.  Some simply state extend a zone of protection to the dripline.  While others are more specific, stating 1ft to 1.5ft for each inch of DBH away from the trunk.  These standards are guidelines.  Tree species, size, age, perceived condition, and vigor all play a role in setting up a final tree protection zone.  Younger trees (species dependent) can probably stand a little less protected soil space compared to a mature tree.

We also need to get away from the thought of a 'tree protection zone,' and start considering a soil protection zone.  After all, its the soil the tree lives in post-construction that will determine overall health in most situations.  If we can't get the desired radius from the trunk on one side of the tree, then consider extending the radius of protection zone further on another side of the tree.  Don't think in minimums, think in maximums.  What is the maximum amount of soil I can protect around this tree?  Numerous studies show that soil volume has a direct effect on tree health and size.

Below are some pictures from a tree and soil protection zone we installed a few weeks ago.  In this case, an addition was being added to an existing home.  We were limited by what area to protect by where the addition was extending, the road, and a driveway.  In this case root pruning was in order to make clean cuts vs. the ripping that would occur when an excavator found the root.

The site and tree (Carya illinoinensis)

A trench was dug using an Airknife to expose roots that may interfere with construction. 
Example of a clean cut root.

The final tree protection fencing. We plan on creating signs to hang on all sides of the protection zone explaining what it is and why it's there.

Sunday, May 12, 2013

I smell something ferty.

Something often forgotten is that our NPK fertilizers and recommendations are based mainly on agriculture.  Most often farmers plant multiple acres of the same crop.  The crop grows from seed to maturity in these fields, absorbing all the elements essential for plant growth from the soils.  When the crop is ready for harvest the entire plant is removed from the site leaving bare soil.  Even when fields are rotated this process happens often enough to burden the soil.  In these situations, complete fertilizers with high NPKs are necessary to replace elements robbed from the soil when plants are taken from the site.

Landscape trees and soils are managed in completely different ways.  While top soils are usually stripped and vegetation removed during the construction process, it's usually a one time event.  Most soils are still able to retain many of the elements essential for plant growth.  Trees, shrubs, and other plants also produce exudates.  Though still not fully understood, exudates promote soil micro-organisms which produce available soil nutrients over time. 

Many studies comparing fertilizers and methods of fertilization often show trees respond best to simple correct mulch applications.  Trees have evolved in forests where leaves, branches and trunks are left to decay.  Correct mulch applications mimic this dynamic.

If you suspect nutrient deficiency in a tree you're managing, it's important to identify which nutrients are lacking.  Misapplication of the wrong fertilizer can be a waste of time and money, and may hurt the tree further if one element is raised to damaging levels.

Typical Soil Analysis 

Sunday, May 5, 2013

Tree myths, that's what's up.

This past week I saw an article from The Guardian about tree myths posted by The Garden Professors BLOG  I know what you're thinking, some one else spends spare time writing about plants.  But for-real, it was pretty interesting, and I'd encourage you to give it a read.  Below are my comments on the 9 myths they choose.

MYTH 1 Compost tea suppresses disease:
Compost tea can be a polarizing topic for arborists.  Compost teas are a way to introduce organic matter into the soil.  Over time this can improve soil nutrient availability, texture, and structure.  Compost tea pushers have made many claims, including that foliar application of compost teas can prevent leaf diseases.  That's just silly.  Wetting leaves with seeped organic matter may actually encourage the development of leaf diseases.  Most leaf spot fungus require a cool wet environment to proliferate, and spraying leaves with compost teas may provide the moisture.

MYTH 2 Lighten clay by adding sand:
I've seen arborists attempt to drill holes in clay soils and back fill the holes with sand, or a large aggregate like stalite.   The problem with this strategy is it ignores a basic principle of water.  Water does not move in between different textures well (i.e. course texture aggregate to a fine texture clay).  So when this management strategy is employed there is still poorly drained clay with sand filled holes full of water.

MYTH 3 Young trees should be staked:
Trees need to move naturally in the wind to put on reaction wood and build taper.

 MYTH 4 Sun through water burns leaves:
 This seems commonly reported on Japanese maples. In most cases it's actually fungal leaf spot, which really is just an aesthetic issue.

 MYTH 5 Tree wounds need dressing:
Most decay fungi need moisture to survive. Painting an open wound can allow moisture to build up behind the sealant, thus creating a perfect habitat for fungi. Now there have been some studies that show some wound sealants may discourage some insect pests from invading new tree wounds.

 MYTH 6 Biodynamic is best:
Using astrology to pick days to plant?  I suppose it would make sense to some early 20th century gardeners. 

MYTH 7 Gravel helps containers drain better:
Once again, water does not like to move between different textures. Putting gravel at the bottom of a pot has the exact opposite effect, keeping water in the finer texture soil longer.

 MYTH 8 Add bone meal and compost when planting trees:
Digging a tree, transporting it to a new area, and then planting it in a foreign soil is a big stress to a plant.  Throwing it in to a super nutrient rich media, believe it or not, can traumatize a new transplant.  Caution needs to be taken when choosing what type of amendments are being put in to the soil.  As the article states, adding to much of an element, like phosphorus, can inhibit plant growth.  More may often not be better, especially in the landscape.

MYTH 9 Natural is safer:
There is no such thing as a safe poison.  Be it found in nature or man made, poison is poison.  We use pesticides to kill pests and diseases.  Some are less toxic than others, and some have different modes of action.  When choosing a pesticide the mode of action, its persistence in the environment, etc. should be your deciding factors.  Not that it has an OMRI stamp and is made from dandelions.