Recognising plant nutrient deficiencies

Watch this short video guide for advice on how to recognise plant nutrient deficiencies.

A table displaying which months are best to sow, plant and harvest.
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To do

Do not To do in January

Do not To do in February

Do not To do in March

Do To do in April

Do To do in May

Do To do in June

Do To do in July

Do To do in August

Do not To do in September

Do not To do in October

Do not To do in November

Do not To do in December

Whether grown indoors or outdoors, all plants can show signs of nutrient deficiencies. In this short video, David Hurrion, BBC Gardeners’ World Magazine, takes you through the basic nutrients plants need to stay healthy, and how to spot the symptoms of deficiencies.

Recognising plant nutrient deficiencies: transcript

Not every spot, hole or deformity on a plant means that it has a pest or a disease. Sometimes those deformities or those irregular growing habits can be down to a lack of nutrients that the plant is receiving.

So, for example, if a plant is growing tall and spindly with small leaves, then it might need more nitrogen. If it's not producing very much in the way of fruit, then it probably needs lots of Potash. And down at root level, if the plant doesn’t get enough phosphate, then the plant can become unstable in the ground, or it might not be able to pump up the water and the nutrients to the plant, which would affect its general health. So, it’s important to understand what the plants need in the way of nutrients, so that they can stay healthy and give you the best results.

Meantime, under glass, plants rely on you for absolutely everything, both for watering and for their nutrition, and those nutrient deficiencies can show up very, very quickly indeed. This tomato, for example, has gone very yellow, and that means that it needs more nitrogen. It’s started to become chlorotic, lacking in chlorophyll. And so, if we give this a quick dose of high nitrogen fertiliser, the plant will green up and it will grow away strongly. And the same thing applies for cucumbers where you’re growing those under glass. They can very often become chlorotic very quickly, just in a matter of a couple of days.

But the main problem really, is with yellow speckling on the leaves. This tomato here has started to lose its chlorophyll between the veins on the leaf, and that indicates that it needs a big boost of calcium. And the best way to do that is to give the plant some Epsom salts. But also, in order to get the plant to produce lots of fruit,
we need to give lots of potash – potassium feed, and that will encourage the plant to produce flowers and fruit. Sometimes you can overdo that and where you give too much potassium to the plant, the leaves will start to become bronzed and sometimes reddish in colour. But that’ll keep it pumping out more and more flowers and more and more fruit.

But nowhere are nutrients more important than here, on the veg plot, where the sorts of feeds that you give plants will give you particular results. So, for example, if you want to grow leafy crops like chard, celery or lettuce, then you need to give them plenty of nitrogen to encourage that strong leafy growth, which is the bit that you’re going to eat. When it comes to root crops like beetroot or carrots or parsnips. Then they need plenty of phosphate to encourage good, strong root development that makes a biggish root that you can eat. And when it comes to pods and fruit, like this courgette, then you need to give them plenty of potash, so that will encourage flowering and then development of the fruit.

Without those key nutrients, the plants will just give a fairly average performance. But with those nutrients, you’ll get a bumper harvest and you’ll get the very best from your garden. There are a number of small micronutrients that some plants need as well, but generally they get those from the average soil in any garden so don’t worry too much. Give them the major nutrients and you’ll get the best from your plot.