By this time in the growing season, most of you have gotten the seeds in the ground and are so excited as you watch the plants grow. With some people, especially the beginners, the excitement is beginning to wane. Why do you ask? Well, the leaves are starting to show a yellow color and not the vibrant green that they had just a few days ago. When this happens the old stand by of, "You have an Iron Deficiency" is heard. Many times this is not a true observation. In this segment, we will look at the yellowing and address it in its true light and that is this, STRESS. The plant is stressed and the first tale tail sign of stress is the yellowing of the leaves. So we will look at the symptoms of stress in plants and some solutions. I am not sure which stress is the most vital to address and which one is of very little significance as anyone will cause the same result as the other, that being a poor performance from the plant and in some situations, stress will cause the plant to die.
Nutrient Deficiencies and Nutrient Over Load; The nutrient deficiencies can be one or many. Yes, Iron is one of them. Yet, Nutrient Over Load can cause pretty much the same symptoms, from all appearances. However, upon close examination, one can usually determine which area is the culprit. One of the first steps to ensure that the plant gets proper nutrition is to make sure the nutrients applied are worked into the ground or placed below the root zone or rootball for most seeds. The seeds have enough nutrients within the seed to get the plant started and on its way. By having the nutrient below the seed, the seed will sense where the next meal is and sent the roots into the direction and a connect can be made and the new plant feed. Most of the time this is a few inches below the main rootball structure of the plant. If the Nutrient Load is too far away then the plant will not have enough reserves to hold it over until the roots can connect wit the food supply. So the plant will begin to show stress and the cause is a deficiency. Sometimes a deficiency is simply a lack of enough of overall nutrients or a lack of certain nutrients. In this case, it is just as bad as no nutrients. When you have a nutrient overload, it can actually cause a nutrient deficiency of sorts. The reason for this is that the performance of the plant will only rise to the least amount of a given nutrient within the required nutrients. In this case, it is known as a limiting factor. However, an overload of a certain nutrient, such as Nitrogen. which is a common occurrence in some gardens, which will cause the plant to go into a hyper-growth mode. In this case, it is usually in the form of an overgrowth of leaves and stems and no fruiting. I did this very thing one year in a small greenhouse that I had and I had it full of Tomato plants. I had Tomato plants that were six feet tall, with leaves that would cover your face and stem as thick as a shovel handle, but they produced no fruit. They did produce a few blossoms, but they soon fell off. I then realized my mistake, too late. Corrected the situation and the next year, the tomato production was remarkable. The moral of this story is that mistakes will be made, you can recover from them, it might take some time, but there is always next year. Also, you must always remember that every piece of ground will be different and have different nutritional needs. The best way to deal with this issue is to learn about the soil you are growing in and do the best job you can in learning all you can about it. This aspect is best to be done on a local level. Anything beyond a local level is just generalized theory and a shot in the dark at best. I am discussing ideas and theories with you here to give you some ideas that you can work with, many of which when adapted to local conditions will work out for you.
Over Watering and Dehydration; Again, with these areas, we see much the same result. Death of the plants in the end. When it comes to overwatering, it will cause the yellowing of leaves, indicating stress. If you use to much water and/or water too often you will saturate the soil and the water will take up space where the oxygen needs to be and essentially drown the plant. The root system needs to have oxygen as much as it needs water. So it is really best to water deep, which is essentially watering the root system. The root system can have a short term over saturation of water, but it does need to drain off within a short period of time so that the oxygen can follow the water back down through the root zone. If you water too often, you run the risk of saturation or even the other dreaded word and that is dehydration. How is it that you cause dehydration by watering the plants? Usually when people over water they will water the plants once or more times per day and with only a small amount of water. This causes dehydration by watering shallow, so no moisture reserve down within the soil and it also promotes the roots to be lazy and form along the top of the soil where the sparse moisture can be found. So in turn, if you don't water several times per day the roots will dry out and the plant dies. The water holding capacity of the soil is very important for you to understand and how well the soil drains or doesn't drain will help you to get a feel of how much water you need to use and at what intervals.
Heat, Cold Stress, and Sunlight; When you have heat stress you will notice parts of the leaf turning Yellow and other parts of the leaf Dark Green at the same time, almost at the same time. Unless you are right there when you observe this happening, then the likelihood of the plant "giving up the ghost" is almost 100%. Basically you have cooked the plant. Understanding the needs of the plant and its heat tolerance level is very important here. I have talked about different plant types according to the Carbon pathway they use for growth. Plants will use 1 of 3 pathways, they are as follows; CAM, C-3, and C-4. About 90% of the plants use the C-3 pathway. With these plants attention to the heat factor is important. These grow better in cooler heat conditions. Next is the C-4 plants. About 7% of the plants out there are within this grouping. They can handle more heat than the C-3 can but hey do have their limits too. Corn is a C-4 plant, for example. Then the CAM plants, which consists of about 3% of the plants and they have their own way of dealing with heat stress. These are the succulent type plants. All of these have their basis in photosynthesis, which is sunlight, but the amount and intensity is the variable. Then as we move to cold stress. When the plant gets cold it interferes with its ability for circulation of nutrients. The photosynthesis is slowed and the leaf loses its green from lack of photosynthesis. Once that circulation strops, then the liquid expands and we experience freezing of the plant, which usually means the death of the plant, forthwith. You might see the speed of growth closely associated with the temperature on the downside. As the cold gets more intense, the growth slows. Proper selection and placement of seed and plant need to have these factors taken into consideration. This one of the primary reasons why greenhouses are presently so popular. Proper management of a greenhouse will extend the growing season by months and t allows the person to control the growing conditions better than growing in an outdoor environment.
Fungal, Bacterial, and Viral Diseases; This an area that can cover far and wide. In most outside growing, you usually don't experience many of these, and when you do itis usually only one or two. In conditions of being "inside," these are of greater concern. The first signs for these are, again, yellowing of the leaves but with an additional sign such as spots. There are a number of these issues that are out there and when it happens to you, you need to seek local help in determining the exact issue you have and what solutions to seek. As a general rule, when one of these issues breaks out, it is not limited to just you. So someone else locally will have likely experienced the same thing and is in a better position to help you. Sometimes you can have enough time once the issue is identified, to check around, and seek a solution. Many times you don't have enough time to take your time. Thus a remedy must be applied immediately. An experienced person or even your self may very well have a solution at hand as they have anticipated this problem. The problem here is that many times the reason for the issue is a nutritional defense.
Pests; Most of these pests that we see in the garden will cause the leaves to turn yellow and yet the veins in the leaf will remain green. These are things like aphids, ants, grasshoppers, and so on. Sometimes these pests do other types of damage. Usually, these involve destroying the plant at the time of the event. These are things like Raccoons, Deer, Birds, the neighborhood kids, and so on. In the area where I grew up, we used to raid a guy's apple orchard every year. But we didn't destroy any of the trees. On one raid we experienced the sound of a shotgun, don't know if it was salt, BB's, or a blank. The sound was enough for us. We avoided his orchards after that. With the latter ones, you have to use a physical barrier. With the former, you need to identify which particular one or ones it is and use what you feel is best. There are natural as well as synthetic solutions.
End of Report.