Orchid Leaves Turning Yellow

Why are my orchid leaves turning yellow, and how do I take care of this? There are many different reasons or causes as to why the leaves are turning yellow. In some cases, when the lower leaves on your plant turn yellow, it is simply a natural process in the plant life cycle with older leaves dying off to be replaced by newer leaves. In most other cases, yellowing leaves are a sign of distress and will need to be remedied to get your orchid back to good health. So, let's look at some of the reasons why your orchid leaves are turning yellow and how we can return our orchid back to vibrant health. 

Nutrient Issues

Orchid leaves turning yellow from nutrient issues can be caused by either lack of nutrients or from too much care given by over concentration of nutrients.  Lack of nutrients can be caused by either watering constantly without ever feeding your plant fertilizer, and it can also be caused by nutrient lockout or deficiency in the the fertilizer that you are using. Nutrient lockout can occur due to the PH level that your water and combined fertilizer solution is at. Visit our page on fertilizing orchids for more information about proper fertilizing and water ph levels. Yellowing of old growth leaves would indicate a deficiency of one or more mobile nutrients, nitrogen, phosphorus, potassium, magnesium, molybdenum and chlorine. Yellowing in the newer growth leaves would indicate a deficiency in one or more of the immobile nutrients, calcium, boron, iron, sulphur, manganese, copper and zinc. Identifying a nutrient deficiency can be achieved with a nutrient deficiency key chart, a local agricultural extension or university with an agricultural curriculum. Here is a good beginner's guide to identifying nutrient deficiencies. Once you have identified the deficiency, you can adjust the water ph and fertilizer ratios to supplement with the deficient nutrient. Visit our pages on fertilization for best practices. 

Fertilizer Toxicity

Fertilizer toxicity occurs when we feed orchids too much concentration of fertilizer.  In nature an orchid would only receive 40 to 60 ppm of nutrients from rainwater. We can be a little more generous when it comes to fertilizing orchids in cultivation, in our opinion a safe range of 120 to 160 ppm of total dissolved solids is beneficial for most species of orchids. Parts per million (ppm) can be measured with a total dissolved solids meter. Fertilizer toxicity, often referred to as fertilizer burn can usually be recognized as yellowing and browning that starts to occur at the tips and outer edges of the leaves. Unfortunately, this can be a very similar symptom to a nutrient deficiency and it can be difficult to make a diagnosis of which cause is the culprit. If this is a prized orchid, and the nursery you bought it from has a very experienced orchid grower, you could ask to bring the orchid in for a diagnosis. Since that is not always an option, the best steps to take would be to flush the orchid and potting mix by soaking it in either rainwater, distilled or reverse osmosis water for 30 minutes, then do this twice more, replacing the water that you are soaking in with fresh water for each soaking. Follow that with running water through the medium for 5 to 10 minutes.  Then read our page on advanced fertilizing to get more precise about how you feed your orchids. There is no one solution for all orchids in terms of fertilizer, however it is better to feed minute amounts of fertilizer on a regular basis, using one of the three recommended sources of water (rainwater, distilled, or reverse osmosis) and paying attention to the ph level of the water and adjusting it. This will eliminate many issues related to nutrient deficiency or nutrient toxicity. 

Sunburn

When it comes to orchid care, leaves turning yellow could be a symptom of sunburn. Sunburn is easily identifiable, and will appear in splotches on your leaves, turning yellow and brown. Orchids should never be in direct hot sunlight. Many orchids will do fine with very early morning or late, late afternoon cool sunlight, but direct hot sunlight will burn your leaves and kill your plant if you do not catch it in time. Sunburn can also be caused by placing your orchid too close to an artificial light source. The remedy for this is simple, visit our pages on orchid care light requirements and move your orchid immediately to a location where it is not getting direct hot sunlight. 

Root Rot

A fairly common reason for orchid leaves turning yellow can be root rot. Root rot, generally caused by overwatering and keeping roots constantly in saturated media is probably the number one mistake that beginning orchid growers make. Remember, most epiphytic and lycophytic orchids in nature grow with their roots exposed to air, and get to dry out between rainfalls.  Orchids with root rot can be saved, but will need some extra special attention for a period of time. To save an orchid with root rot, remove it from the media and  inspect the root system carefully. Use a sterilized cutting shears to remove all blackened and papery dead roots. If you still have a fair amount of live roots, you can simply repot the orchid in some new orchid growing medium such as fir bark or sphagnum moss and water less frequently than you have been doing to date. If, however, there are few roots left, then more care will have to be taken to revive and revitalize your orchid. In this case, it may be best to keep your small root system in a container with a small amount of sphagnum moss wrapped around the root system for a period of time. Allow the sphagnum moss to dry out between waterings. Sphagnum moss has a crunchy sound when dry, which you can test by simply pressing on it. At this point, your orchid is in intensive care, so pay close attention to it for the next few months.  Follow the links in the navigation to read more about watering.

Dehydration

Dehydration or lack of water can be related and have similar symptoms to root rot, in that there are no longer enough viable roots to hydrate the orchid. The other cause of dehydration is neglect and under watering, the end result being the same as overwatering in that the roots shrivel up and die. To rehydrate an orchid, remove it from its container, clean away the growing medium from around the roots, and cut away any dead, papery roots. Hydrate the roots by placing them in a container where they are almost completely immersed in water.  Keep the leaves, stems, crown dry and out of the water. Immerse for six to twelve hours, then remove and allow the plant to air out for twelve hours or overnight.  Repeat this process for a few days before repotting the orchid. Follow the steps in the preceding paragraph if you have very few roots left on your orhid. Afterwards maintain a regular watering and feeding schedule. 

Crown and Stem Rot

Another possible reason for orchid leaves turning yellow is crown rot. Crown rot happens when water accrues and sits in the crown or leaf axils of an orchid. In their natural habitat, they typically grow sideways with the crown and leaf axils tilted, so rainwater never gathers in the orchid.  Because in cultivation, we like to place orchids in pots, keeping them upright, careless watering can result in water accumulating in the crown or leaf axils which can lead to fungal infections and death. Crown rot is almost impossible to reverse, so the best solution is to avoid this problem in the first place by being attentive when watering. Dry out any accidental splashes into the crown or leaf node areas with a paper towel and provide some air circulation with a fan. 

Natural Part Of The Lifecycle

If you are providing excellent care, orchid leaves turning yellow may simply be part of the natural life cycle. As orchids age, some of the leaves may simply age, turn yellow and fall off. Phalaenopsis tend to lose the oldest leaves every one or two years after they reach a certain age. Bulbophyllum, Cattleyas, and Dendrobiums have outer sheaths that dry up and turn yellow. These dry outer sheaths may simply be peeled and removed to provide a better aesthetic look.