Tissue Sampling Trees

Spring is in the air and for most lawn and landscape practitioners this means getting the season off to the best start possible.  Many of the beginning steps such as soil sampling and early season fertilizer applications may already be implemented, but one practice to be ready for this year is tissue sampling your trees.

Soil sampling is an excellent tool to help understand what is present in the soil, and potentially available to the tree(s).  When sampling trees, is it paramount to sample within the drip line of the tree and 0-18 inches of depth.  Most samples are taken at 12 inches deep since this is the most common depth possible taken with a manual soil probe. 

The drip line, or the outside edge of the tree’s canopy, is a good indicator of where the majority root mass is underneath the soil surface.  Any samples taken outside of the drip line will not be the best representative sample.  Soil samples are necessary to make an agronomic application or amendment to better the health and/or productivity of the tree, but soil samples are limited to only knowing what is present at sample depth.

Unlike row or vegetable crops, the root systems of trees can be immensely different.  They often cover large areas both vertically and horizontally.  This means that the soil sample is a very small snapshot of the big picture.  Whereas a soil sample is taken at root depth, or root accessibility, for root and vegetable crops, tree care needs more input information.

This is where tissue sampling helps complete the story for tree care.  A tissue sample is a representation of what is currently in the tree itself.  This, in conjunction with a soil sample, will show what is available for uptake from the soil and how the tree is utilizing these nutrients.  It is not uncommon for a soil test to report different levels of nutrients in comparison to the tissue analysis.  Many variables can affect nutrient uptake.  The root structure itself is a main contributor.  Outside forces like compaction, nematodes (pests), diseases and weather, to name a few, all influence nutrient uptake. 

In most cases a tissue sample for a tree is comprised of mature leaves from new growth for deciduous trees and 2-3” terminal cuttings from new growth for conifers. Contact your ALGL regional agronomist for more information.

By the time trees show signs and symptoms of nutrient deficiency, it is usually too difficult to change the tree nutrient value quickly.  There are some commercial applications for directly injecting available nutrients into the tree, but this can be a costly procedure.  Tissue samples of healthy leaves are usually taken mid-summer annually.  This is when the tree is most stable with fully developed leaves.

Soil and tissue sampling work together in coordination when implementing the best nutrient management plan for trees.  Soil samples show what is available whereas tissue samples show what is being utilized.  Together, the results are interpreted as the best option for that species, environment and soil type.