So you have decided to grow spinach in your home garden this year. You go outside to your vegetable garden to check up on your plants. However, instead of a lush, vibrant cluster of dark green spinach leaves, you are greeted by a sad bunch of spinach leaves many of which are turning yellow. So what’s the deal with yellow spinach leaves and how can we prevent them?
There are many different reasons as to why spinach turns yellow however, they all stem from the fact that the spinach plant is under some form of stress. Common stressors include insufficient or excessive watering, disease, lack of nutrients, drastic increase or decrease in temperature, or transplant shock.
While all forms of stress result in yellow spinach leaves, each of them are treated and prevented in different ways. Therefore, it’s crucial to understand what form of stress is causing your spinach to turn yellow so that it can be properly treated and prevented.
Like all plants, spinach requires water. If your spinach doesn’t receive enough water, it will begin to wilt, turn yellow and eventually die. However, overwatering your spinach can just as easily harm your spinach and cause it to turn yellow. When spinach receives too much water, the roots get drowned out and they become susceptible to root rot. Root rot will turn your spinach leaves yellow and can kill the spinach plant if it is severe enough.
So what’s the sweet spot when it comes to how much water your spinach should be receiving? Spinach should receive around 1 to 1.5 inches of water per week. The key is to keep the surrounding soil consistently moist. This way, your spinach will stay hydrated but also won’t be drowning and developing root rot.
Spinach is susceptible to its fair share of plant diseases many of which can cause its leaves to turn yellow. Fusarium wilt for example, is a disease that affects many different kinds of plants including spinach. Fusarium wilt will cause the leaves on a spinach plant to turn yellow, wilt and wither off the plant typically starting at the base and working its way up.
If your spinach shows signs of fusarium wilt, prune the infected areas immediately to prevent it from spreading. Do not compost infected plant material as it the disease will make its way back into your garden when the compost is added. If the disease persists, continue pruning the infected areas followed by an application of fungicide.
Another disease known to commonly cause spinach leaves to turn yellow is downy mildew. In addition to yellow spots appearing on the leaves, downy mildew will also develop a fuzzy gray material on the underside of the leaves.
While there is not much you can do to treat downy mildew other than pruning the infected leaves and discarding them, preventing it from occurring in the future is rather simple. Downy mildew thrives in wet environments so avoid watering your spinach from overhead. Instead, water your spinach at the base of the plant to keep the leaves dry. Downy mildew also prefers cooler temperatures of 65°F (18.3°C) and below, so avoid planting your spinach too early of too late in the growing season. Lastly, try selecting varieties of spinach that are more resistant to downy mildew. Such varieties include Olympia, St. Helens, Meridian, Baker and Polka.
Lack of Nutrients:
Another common reason for spinach turning yellow is due to it receiving a lack of nutrients. Spinach plants are heavy feeders so it’s important to provide them with a rich, nutrient dense soil. Adding some compost and all purpose fertilizer to your soil prior to planting is highly recommended.
However, if your spinach is already established and growing and its leaves are turning yellow, it is most likely lacking in nitrogen. To amend this, apply a nitrogen based fertilizer such as blood meal to the surrounding soil. Blood meal can either be worked directly into the surrounding soil or be diluted in water and applied through watering.
A sudden change in temperature can also cause spinach to turn yellow. Spinach is a cool weather crop so excessive heat often causes spinach to turn yellow and bolt. Because of this, spinach should be planted early in the spring or during the fall as to limit its exposure to warmer temperatures.
If your spinach is already exposed to the heat, provide it with some shade to help keep it cool. Applying a layer of mulch around your spinach can help protect the soil from the heat and keep it cool.
Alternatively, a shade cloth can be used to protect your spinach from warmer weather. Shades cloths are a great option because they allow sunlight and water to pass through them while simultaneously protecting plants from the excessive heat. Shade cloths also come in different intensities depending on how much shade you need. For spinach, a 50% shade cloth is adequate.
If you are growing spinach in a warmer climate, choosing heat resistant spinach varieties may be the best option for you. Varieties such as Olympia and Bloomsdale are naturally more heat tolerant thus making them less likely to turn yellow and bolt.
Another cause of spinach turning yellow is Transplant Shock. When plants get transplanted, they are often harmed in the process. The change in environment and light exposure the roots receive when being transplanted puts a lot of stress on the plant. This is known as transplant shock. When spinach experiences transplant shock, it often experiences stunted growth as well as yellowing of its leaves.
While transplant shock can’t be completely eliminated, there are a few ways to mitigate its effects. The easiest way to reduce transplant shock is allow your spinach to develop more before transplanting. Allow your spinach 3-4 weeks of growth before you transplant. Plants will experience higher levels of transplant shock the younger they are when transplanted.
Another easy way to mitigate transplant shock is through the use of seaweed extract. The vitamins and amino acids in seaweed extract help drastically reduce transplant shock when transplanting your spinach.
Along with reducing transplant shock, seaweed extract provides other benefits for plants including promoting a stronger root system and faster growth; overall, a great benefit for not only spinach, but all plants in your garden!
If none of the reasons listed are causing your spinach to turn yellow it is likely just getting old. There is not much you can do to combat aging, but can aim to harvest the outer most leaves of your spinach plant first as they are the oldest and will turn yellow the soonest.
Hopefully by now you have an understanding of why your spinach is turning yellow. While there can be many reasons as to why spinach turns yellow, it will ultimately be due to some form of stress the plant is experiencing. At the end of the day, if we take good care of our spinach then we will be rewarded with vibrant cluster of dark green spinach leaves rather than a sad bunch of yellow spinach leaves.