Ever see chlorotic or stunted leaves and wonder if it could be a particular nutrient deficiency? Soil nutrient testing can be a good tool to assess levels of macro and micronutrients. We use soil tests to help make decisions about adding fertilizer and organic materials to the soil. But what soil tests don’t tell you is how much of the nutrient is available for plant uptake.
Quite often when we see symptoms of what looks like nutrient deficiency, the next best step is to take leaf samples for foliar analysis. A good rule of thumb is to take enough symptomatic leaves to fill a paper lunch bag. And paper is the way to go (not plastic). Samples left in plastic will begin to degrade, potentially changing the nutritional content. Where possible place the leaves out in a thing layer to dry and keep them dry until you submit them for analysis. Try to select leaves from the middle of this year’s growth and avoid the very youngest or oldest leaves. Try to be consistent about where you take them on the tree. Usually 40 maple leaves is a good sample (about 100 grams fresh weight). The smaller the leaf, the more leaves you will need.
If possible, take a comparison “healthy” sample from the same species (or cultivar/variety) from trees that are not immediately on the same property. Remember that trees can be experiencing nutrient deficiency symptoms for years before they show any symptoms of stress. So the nutrient levels between a healthy looking Quercus robur and a chlorotic Quercus robur on the same property could be….very very similar. If you can’t find a healthy species growing just off-site, there are “book values” that you can refer to and most labs include them on foliar tests now.
Ontario labs that do tissue testing include A&L Labs in London, SGS Labs in Guelph, Stratford Agri-Analysis and University of Guelph Lab Services. Analysis should run about 40.00 per sample and it can take a week or two depending on how many samples the lab has to run. But the information is very valuable and can be used to make long term nutritional recommendations to grow healthier trees and shrubs!