Herb gardens bring fragrance and life to even tiny spaces, with the added advantage of always having fresh seasonings for your recipes. Many of these plants grow outdoors or indoors, provided that they have the appropriate conditions, including proper light and temperature. If a number of these conditions are not appropriate, the herb plants might develop yellowish leaves. Correcting problems one at a time makes it possible to discover and treat the issue.
Lack of Fertilizer
Herbs are normally simple to take care of, but they nonetheless require fertilizer to grow correctly. Yellowing leaves can be a signal the herb plant lacks adequate nutrients, especially nitrogen. Start providing the herb a balanced liquid plant food, such as 14-14-14, once a week once you normally water the plant. Dilute the fertilizer to half strength to reduce fertilizer burn, which can also lead to yellowish leaves.
Too Much or Too Small Water
Most herbs have a tendency to favor moist, well-draining soil. Herbs grown outside might require that you add a soil amendment, like mud, if the herb garden soil is too dense. Indoors, choose a sterile potting soil that includes materials like peat moss to help with drainage. The roots should stay moist, meaning watering at least once every week indoors and much more often outside, especially in the heat of the summer. Yellowing leaves frequently signal that the herb is famished for water and also is falling leaves to conserve energy, but it also can mean the roots are excessively wet and beginning to rot. Press your finger about an inch into the ground a couple of days after you water. If the soil remains wet or soggy, don’t use as much water the next time or distribute the waterings. If the soil is totally dry, water more frequently and use more water each time.
Temperature and Light
Although the precise temperature and lighting demands of herbs change, generally speaking, they need five or more hours of full sun daily outside, and possibly more if they get indirect lighting through a window. Most need daylight temperatures in the 70s Fahrenheit, although they likely can survive short bouts of higher temperatures. If the yellowing leaves are in the base of a bushy herb plant, it’s likely their color is changing because the leaves are being destroyed by leaves higher on the plant. Picking off the yellow leaves will not hurt the plant, however try to strategically prune it once you harvest the herb for cooking so it’s less bushy. When temperatures are high, consider moving outdoor plants to more shaded areas or water more frequently, sometimes daily, until the hot weather passes.
Other Potential Issues
Yellowing happens for a number of different reasons, including the need for a larger pot because the plant grows. Should they become rootbound, in which the roots start growing in circles round the interior of the pots, transplant them into pots around 2 inches larger in diameter. In addition, it is possible the soil’s pH is not ideal for the herb development. Sage (Salvia officinalis), as an example, which grows outside in U.S. Department of Agriculture plant hardiness zones 6 through 9 and indoors throughout the country, requires a soil pH of 5.5 to 6.5. Some disorders, like fusarium wilt, cause leaf yellowing also, although the yellowing typically begins as stones on the leaves or accompanies wilting along with other symptoms like stunted growth. In many cases of disease, disposing of this plant and soil in a plastic bag would be the ideal option to protect against the spread of this disease to other herbs, although eliminating infected leaves is occasionally sufficient.