Why Are My Hostas Turning Yellow and Brown?

Hostas (Hosta spp.) are usually prized for their foliage, but yellow and brown leaves are not the most desirable of rewards. Growing in U.S. Department of Agriculture plant hardiness zones 3 through 8, they thrive in rich, moist soil and can tolerate full shade. Healthy hostas glow in shades of blue, green, gold and cream. Unfortunately, that fabulous foliage will fade if hostas are cared for improperly or are damaged by pests or diseases.

Anything that damages the roots of hostas can cause yellow and brown leaves. The damaged roots are unable to absorb nutrients and water, and as a result, the plant suffers or even dies, depending on the extent of the damage. Although hostas prefer moist, cool soils, heavy and wet soil in spring and winter can lead to root rot -- a fungal disease that rots away the roots. Well-drained soil is a must for these plants, and pots containing hostas should have a hole in the bottom to allow for good drainage. Burrowing animals, such as voles, can also damage the roots of the plants. Voles prefer to create their tunnels under lawns, mulch and areas with loose soil, so try planting your hostas among tree roots or near other underground barriers that will naturally block tunneling animals.

Many home gardeners use hostas to brighten up shady corners of their gardens, but hostas are brighter when they receive some sunlight. They key here is knowing how much is too much. Some hostas are much more tolerant of direct sunlight than others. Too much hot, direct sunlight can scorch the leaves of some varieties, causing them to turn yellow and brown. Choose varieties that can withstand the sun, such as "Sun Power" hybrids. In general, home gardeners in USDA zones 6 and above should avoid planting hostas in direct sunlight, according to the Missouri Botanical Gardens website. Making sure your hostas get enough water during hot, dry periods can also help.

Hostas can sometimes suffer from something called "Virus X," which causes the leaves to develop dark spots, rings, browning or twisting of the leaves. Unfortunately, there is no cure for this disease. In addition, these symptoms often mimic those of spontaneous mutations, or sports, which some home gardeners find desirable. In general, however, it's best to remove plants that suffer from these symptoms, especially if they appear all over the plant. If they appear in just one section of the plant or on only a few leaves, you can just remove those leaves.

Fungi don't just affect the roots of hosta plants. They can also damage the stems and leaf petioles. In fact, petiole rot is a common and serious affliction of hostas. When this happens, the leaves are cut off from the main stem and are unable to receive nutrients. They turn yellow and brown, and pull away easily from the plant. Southern blight, which rots the stem, and anthracnose, which usually attacks the leaves themselves, are also fungal diseases that can cause hosta foliage to turn yellow and brown. Avoid these problems as best you can by watering at the ground level, rather than from overhead, and by watering early in the morning so that the sun can dry off the leaves. Overcrowded conditions can also contribute to fungal diseases, so make sure air can circulate around your hosta plants.