Sage, or Salvia officinalis, is a herbaceous perennial plant that may reach a height of up to 2 feet and 1/2 inches. It is a member of the mint family. According to the Missouri Botanical Garden, this plant thrives in plant hardiness zones 4 to 8 of the United States Department of Agriculture and is a mainstay in kitchen herb gardens due to its silvery-gray, slightly fuzzy leaves and white to lavender flowers. It also combines well in perennial flower beds in these zones. Sage is a generally resilient plant, but its leaves may become yellow for a number of reasons, including those related to the climate and pests.
Sage plants are susceptible to a wide variety of diseases, some of which cause the leaves to become yellow and others to wilt. Sage plants are susceptible to a variety of diseases, including leaf spot, powdery mildew, and rust, according to the Clemson Cooperative Extension. On the surface of the leaf, leaf spot may seem like anything from tiny spots to enormous yellowish blotches. It is produced by many different types of fungus and can take on a variety of forms. On the leaves of sage plants, powdery mildew manifests as a white, powdery spore that causes the leaves to become distorted and eventually causes the plants to perish. Rusts, which are also caused by fungi, manifest themselves on the leaves of sage plants as dried, discoloured lumps. Planting sage in regions that are exposed to full sunlight, have adequate air circulation, and do not allow water to pool will prevent infections from manifesting in the first place.
Sage plants may have their health negatively impacted by significant shifts in the weather, such as an extended period of hot, dry weather or multiple days in a row of precipitation. Sage plants need full light and soil that is medium to dry for optimal growth; however, insufficient watering causes the leaves to become dry and brittle, which then turns the leaves yellow and causes them to fall off. During periods of drought, it is important to give the sage plants a sip of water once each week. Sage plants suffer additional stress when they are overwatered and may develop root rot or damping off at the soil line if they are surrounded by moist soil. Yellowing and wilting of the leaves is an early warning indication of overwatering.
However, aphids and thrips will feed on the leaves of sage plants. In general, insects will not bother sage plants. When present in great numbers, the insects may cause structural damage to sage leaves, causing them to become yellow, or leave behind regions on petals that are pale and discoloured. Aphids are a kind of pest that are very small and have soft bodies. Their colour may vary from practically transparent to black. They do this by cutting holes in the plant’s leaves and other delicate portions with their jaws and sucking the juices out. The University of California Agriculture and Natural Resources describes thrips as another kind of bug that is almost impossible to see due to their tiny bodies and fringed wings. Thrips feed on the fluids that are produced by plants. Both aphids and thrips are capable, when feeding on sage plants, of transmitting illnesses that cause harm to the plant’s leaves.
The leaves of sage plants may become discoloured and misshapen when they are missing certain nutrients, which also causes the plants’ development to be stunted. In most cases, nutritional shortages are brought on by issues with the roots of the plant. These issues prevent the plant from absorbing minerals, such as nitrogen and iron, that are present in the soil. Make sure that sage plants are situated in soil that has enough drainage in order to assist in the prevention of root issues. You may identify what nutrients your sage plants are lacking by testing the soil in your garden with a home test kit, which can be found at most garden stores. When fertilising your plants, use fertiliser of the slow-release kind that contains just the essential elements for plant growth.