Just as you need nutrients to survive, so do plants. Plants obtain their nutrients from the soil they are planted in. Bad soil, sick plants. I found this out the hard way my first year planting. Because the top soil I bought for my raised beds came from a forest, I assumed my plants had all the nutrients they needed to thrive. My new plants told me otherwise.
Three weeks after planting my lettuce – about two to three weeks before expected harvest – it still looked like it had just come through the ground. My beets and turnips were spindly and weak, unable to hold up their own leaves. I knew something was wrong and a soil test confirmed it. Although my soil had plenty of potassium (thanks to the trees in the forest), it was totally deficient in nitrogen and phosphorus.
Plants need many nutrients to thrive, but the three main ones are nitrogen (N), phosphorus (P), and potassium (K). A deficiency in any of these nutrients will lead to problems in growth and fruit production.
Nitrogen is necessary for making chlorophyll – the substance that makes leaves green. It is responsible for lush, vigorous growth. A deficiency in nitrogen will cause the leaves to turn pale green or yellow, starting with the older leaves on the bottom of the plant. Plant growth will also slow down or stall, making an older plant appear to be much younger than it is.
Phosphorus is necessary for root formation and growth, photosynthesis, and seed and fruit production. A deficiency in phosphorus will cause thin or weak stems, stunted growth, delayed maturity, and a reduction in flowering and fruit production. A severe deficiency will cause the leaves to turn bluish-green or have purple veins.
Potassium – also known as potash – is necessary for the overall health of the plant. It keeps plants growing, helps with the plant’s response to drought conditions, and strengthens the plant’s immune system. It’s also responsible for the quality and flavor of the fruit. A deficiency in potassium will cause an increase in disease problems, quick wilting in dry spells, and poor quality fruit or fruit without good flavor. A severe deficiency can cause brown spots on leaves, yellowing leaf edges, or yellow or brown veins.
As you can see, some of the symptoms of deficiency are similar for each nutrient. The only way you can know for sure is by testing your soil. Testing before you plant is recommended, but sometimes you may have to test again if your plants aren’t growing well. With the test results, you will know what nutrients your soil needs.
You don’t have to be a botanist to know something isn’t right with your plants. Just spend a little time with them. They’ll tell you when they need help.