And you thought that plants had nothing to say. Let something in their environment or diet get out of whack, and they can have plenty to say. Sometimes they even scream – silently. It’s important that you know what a healthy plant in your new crop looks like, otherwise the early signs of trouble won’t be recognized.
Yellowing leaves is technically known as ‘chlorosis.’ In the ground or standard potting soil growing conditions, yellow leaves can be caused by over drying of the soil. In a hydroponic growing situation this generally communicates that there is something wrong with your nutrient solution. As we all know, there’s nothing like being deficient in a dietary need to make one look a bit off or put a damper on the energy needed to perform daily tasks.
Saying that the leaves are yellow isn’t enough of a description to pinpoint exactly what might be amiss with your solution though. What kind of yellow, and where on the plant are these sad looking leaves located? Are you seeing other symptoms along with this yellow foliage? Hopefully, this discolored foliage signal has recently appeared, because untreated symptoms are the forerunner of more serious decline in your crop.
Solid yellow leaves are usually connected to a nitrogen (N) deficiency, but the first sign is the plant turning lighter green than it should be. Stunted growth will be seen, showing up most keenly in the tops and lateral branching. Your plants will also exhibit a spindly appearance. This deficiency starts with the older leaves toward the bottom of the plant and gradually moves upward to newer growth. Nitrogen deficient plants loose the mature leaves early, mimicking problems seen from lack of moisture at the roots.
Yellowing between the veins can also be seen in nitrogen deficient plants as they turn from paler green to yellow, but this also can be a sign of potassium (K) deficiency. With below acceptable potassium though, the yellowing will be only on portions of the leaves and will be accompanied by scorched looking spots. The scorching or necrotic spots start along the edges of the leaf and eventually begin to move inward. As the condition continues, the symptoms climb upward into the less mature leaves.
Yellow mottling appearing between the leaf veins is a known sign that your plant is lacking in iron (FE). Quite the opposite of the first two descriptions of yellowing foliage, an iron deficiency appears first on the youngest leaves. With severe iron deficiency, the absolute absence of chlorophyll is seen, without mottling. You will see this start out near the base of the new leaves like a central yellow streak that spreads outwards over time.
There are other causes of yellow leaves, such as sulfur deficiency and the beginning stages of some diseases. Each has it’s own unique footprint. You should be monitoring all plants in your growing space regularly. If something looks off, it’s best to identify it and start correcting the issue as fast as possible.
Better yet, test your nutrients regularly with the proper meter to get the most accurate readings on the essentials and micronutrients present. If you aren’t sure what your different plants’ needs are – find out. Hopefully, you realize this is important before you start growing any particular type of plant. The most abundant harvest comes from plants that are the picture of health from sprout to finishing the crop.