Watermelons plants have many different types of leaves. There are two main kinds: green and yellow or brown. Green leaves are those with light color while yellow or brown leaves have dark colors. They look very similar but they do not grow from the same plant. Some varieties of watermelons such as the Fuji, Honeycrisp, and Black Beauty produce only green leaves while others like the Red Devil and Blue Dream produce both types of leaves.
Both types of leaves have their own purpose. Green leafs are used for photosynthesis which converts sunlight into energy for plants. These leaves provide food for the plant when they are young and then they wither away after a few years. When these leaves wither away, the plant will need to make use of other parts of its body to survive. For example, if it cannot get enough oxygen from the air, it may die. If it does not have enough nutrients in the soil to grow properly, it will eventually become stunted and die. The reason why some watermelons plants produce only green leaves is because they are resistant against certain pests that attack plants that produce only yellow or brown leaves.
There are many different types of yellow and brown watermelon leaves. They include the following:
Sunburnt Leaves – these are dark yellow or golden yellow in color and they appear to be burnt. They often look curled up or dry. This is a condition that can happen naturally when a plant grows in an area that is too sunny. These areas may not have enough humidity for the plant so the moisture on its leaves evaporates too quickly causing the burns.
Sunscalded Leaves – these leaves are brown or yellow and they have a white appearance on the underside. They may look wilted or even slimy. This is a condition that is caused by sudden changes in temperature during the nighttime hours. It can be prevented by placing a cloche over the entire plant at night to create a more stable environment for the plant.
Spotted Leaves – these are small yellow or brown spots on the edges of the leaves. They may be caused by bacteria or viruses or they may be a symptom of a nutrient deficiency.
Wilted Leaves – these are dark yellow, brown or red in color and are limp to the touch. They may have a green tint on the topside. This is a condition that occurs when the plant is lacking water. It can also be caused by other types of environmental stressors such as too much salt in the soil, high winds or temperatures that are either too hot or too cold.
Sources & references used in this article:
First Report of Cucurbit chlorotic yellows virus in Cucumber, Melon, and Watermelon in China by …, HF Gu, L Xu, FM Song, JK Brown – … Disease, 2011 – Am Phytopath Society
Some physiological and growth responses of watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] grafted onto Lagenaria siceraria to flooding by H Yetisir, ME Caliskan, S Soylu, M Sakar – Environmental and experimental …, 2006 – Elsevier
First Report of Cucurbit yellow stunting disorder virus in Cucurbits in Florida by JE Polston, LL Hladky, F Akad… – Plant disease, 2008 – Am Phytopath Society
A new bipartite geminivirus (begomovirus) causing leaf curl and crumpling in cucurbits in the Imperial Valley of California by P Guzman, MR Sudarshana, YS Seo… – … Disease, 2000 – Am Phytopath Society
Widespread Outbreak of Cucurbit yellow stunting disorder virus in Melon, Squash, and Watermelon Crops in the Sonoran Desert of Arizona and Sonora, Mexico by JK Brown, JC Guerrero, M Matheron, M Olsen… – … Disease, 2007 – Am Phytopath Society
A tospovirus infecting peanut in Taiwan by CC Chen, RJ Chiu – Tospoviruses and Thrips of Floral and Vegetable …, 1995 – actahort.org
Management Fusarium wilt on melon and watermelon by Penicillium oxalicum by A De Cal, A Sztejnberg, P Sabuquillo, P Melgarejo – Biological Control, 2009 – Elsevier
Detection of Myrothecium leaf spot, a new disease of watermelon by DK Kim, DW Bae, SC Lee, KS Han… – Plant Pathology …, 2003 – researchgate.net