Dealing with Plant Disorders: Nutritional Disorders

By Steve Malsher MCIHort

To round off this mini-series on plant problems, we are looking at disorders. These come in many forms and we will be tackling a lot in this blog, meaning it will be split into 3 parts. Keep an eye out on our social media and mailers for the next parts. Part one looks at nutritional disorders and the effect of soil pH on plant health.

Disorders are plant problems that are caused by the environment in which the plant is being grown. They are often called Plant Physiological Disorders and they tend to be of two types: those caused by nutritional disorders and those caused by non-nutritional disorders.

Nutritional disorders can be broken down into two further groups.

  1. Insufficient nutrients in the soil. This is particularly a problem on sandy soils because nutrients are easily washed out of the soil by rainfall.
  2. Incorrect pH of the soil for the particular plant you wish to grow. Some plants prefer acidic soil (Calcifuges) whereas others prefer alkaline soils (Calcicoles).

Non-nutritional disorders include:

  • Frost
  • Shade
  • Drought
  • Waterlogging

It is possible to avoid all of these disorders by applying a simple mantra, “Right Plant, Right Place”, and I have to thank Beth Chatto for that phrase.

Dealing with Plant Disorders: Nutritional Disorders

Insufficient Nutrients                  

Any soil can be deficient in some nutrients. Some are leached from the soil by rain and irrigation (especially in sandy soils), particularly nitrogen and potassium.

Others may be in low concentrations. This is why we add fertilisers to sandy soils in spring, just before we plant or when the new growth is occurring. Of course, any lack of nutrients will have an effect on your plants, leading to reduced vigour, smaller flowers and lower yield on edible crops. It is of great importance that correct feeding is carried out. Generally, the addition of well-rotted organic material once a year is plenty and only supplementary feeding of inorganic fertilisers is needed if you are growing show plants.

There is a small warning though, overfeeding can be just as damaging as underfeeding. Too much Nitrogen in the soil will lead to “leggy” and soft growth in herbaceous plants leaving them vulnerable to collapsing and insect attacks.

pH Problems

The pH scale is how we measure how acid or alkaline a substance is, including soils. It ranges from 1 (very acidic) to 14 (very alkaline) and 7 being neutral. From neutral, a rise of one on the scale to 8 means that the soil is 10 times more alkaline. A drop of one from neutral means it is 10 times more acidic. Generally, UK soils range from 4.5 to 8.

pH has a large effect on the ability of the plant to take nutrients from the soil. Alkaline soils mean iron and manganese are difficult for the plant to take up. This can cause a disorder called lime induced chlorosis in calcifuges, due to the lack of iron and manganese needed in the production of chlorophyll. It can be seen as yellowing in the margins of leaves with browning of the leaf edges.

Dealing with Plant Disorders: Nutritional Disorders

To overcome this problem, the pH needs to be lowered by adding sulphur or by adding the required nutrients in a form which they can be taken up. For example, Iron chelate (also known as Chelated iron), which is a soluble complex of iron, sodium and a chelating agent used to make the iron soluble in water and accessible to plants. Another name for it is sequestered iron.

Nicholsons are able to accurately measure the pH of your soil and nutrient levels, advising you of treatments to improve your soil.

Next week, we will be looking at some non-nutritional disorders caused by drought, water-logging and frost.