Symptoms of Nutrient Deficiency and Excess
Edited by Dr. Ryan Lee, PhD
An understanding of basic plant nutrition is recommended for those with a serious interest in gardening. The purpose of this feature is to explain the function of the essential nutrients in plants and to provide information about recognizable symptoms in plant material when there is a nutrient deficiency or excess. Following diagnosis it may be possible to improve plant health and vitality by adjusting nutrient levels.
NUTRIENTS MUST BE “PLANT AVAILABLE”
All of the nutrients listed here are essential – plants cannot live without even the least of these. It is not enough that the nutrients are present – they also must be “plant available”. Availability depends largely on soil texture, organic matter, and pH. Therefore it is highly recommended that gardeners start their nutritional program with a high-quality soil test from a reputable testing facility. While Osmocote® Plant Food, the sponsor of this website, provides several essential nutrients and / or brings the concentration of certain nutrients to levels that are available to the plant, its ability to do so is dependent on the soil’s characteristics.
WHERE DEFICIENT/EXCESS NUTRITION FIRST APPEARS IN A PLANT MATTERS
A key concept in understanding plant nutrition is “mobility”. For example, Nitrogen is a very mobile nutrient. When the soil is lacking sufficiently available Nitrogen, a plant will rob available Nitrogen from its old leaf material and move it into actively growing points (from source to sink). Therefore, the deficiency develops on the old leaves first. They turn yellow between the veins as the Nitrogen is wicked out of the cells towards the needy, new growth. Calcium on the other hand, is immobile. Therefore, if a plant finds itself in an environment that has low available Calcium, the symptoms will most likely manifest in the newest growth, as the plant is unable to shunt this nutrient easily. Plants deficient in Calcium will display irregular growth in the newest leaves.
UNDERSTANDING BASIC PLANT PHYSIOLOGY IS KEY IN DIAGNOSIS
From the two examples above concerning Nitrogen and Calcium it is easy to see that diagnosing nutrient deficiency (or excess) requires not only characterizing the symptom but also understanding some basic plant nutrition physiology. If symptoms develop on the old growth, the nutrient is mobile. If symptoms develop on new growth, you are likely dealing with an immobile nutrient. Armed with this knowledge and a good soil test, any gardener should be able to diagnose nutrient related diseases.
DIFFERENCE BETWEEN PLANT ESSENTIALS AND “BENEFICIALS”
Before turning to the review of specific nutrients, there is another category of materials that gardeners give to their plants. Let’s call them “beneficials”, that is, things that might improve plant growth but are not required (things like giving sugar water to a pumpkin). As interesting and helpful as such things may be, they are not essential to plant life and are not reviewed in this article.