Cilantro is a fast-growing herb that is usually ready to be harvested a month after its initial planting. Cilantro is an annual plant, so a new plant must be added to the garden each year. Keep cilantro healthy to encourage the bright green, flavourful leaves that make this a popular herb. Yellow leaves on a cilantro plant indicate a health problem.
Cilantro grows best in full, direct sunlight from which it receives energy. Direct natural light encourages the growth of green, healthy leaves and enables the plant to fight off pests. Grow cilantro in a windowsill if it is growing indoors, or provide the plant with an artificial grow lamp to supplement natural light. Cilantro plants growing in low light or shade produce weak, yellowing leaves that lack the flavour of healthy cilantro.
Plant cilantro in nutrient-rich soil that contains compost or decaying organic matter to provide the plant with nutrients. Supplement potting soil with fertiliser if the cilantro is growing indoors or in a planter. Make sure the soil drains water easily, as waterlogged soil drowns the cilantro's roots, causing it to produce straggling, yellow growth. Use a planter that drains water and make sure garden soil does not have standing water problems when growing cilantro.
Cilantro that does not receive enough nitrogen puts out weak, straggling and yellow leaves. Nitrogen is an essential nutrient for the production of healthy, flavourful cilantro. Add a fertiliser that has high nitrogen content to the soil to keep the cilantro healthy and encourage green leaves. Fertilise the soil twice each year, in early spring and midsummer, to keep the nitrogen content of the soil healthy for the cilantro plants.
Spacing is vital to cilantro plant health. Cilantro plants that grow too close together are forced to compete for root space and space for their leaves, as well as resources like nutrients, water and sunlight. Competing cilantro plants are more likely to produce yellow leaves. Leave at least 15 inches between rows of cilantro plants and 2 to 4 inches between individual plants within the row.