What Can I Do if My Rosemary Plant Is Dying in the House?

Adequate Light

• Check how much light the plant is getting. If the plant was brought indoors, it should have been subjected to gradual lighting changes, from full sun to restricted lighting; otherwise, it cannot adjust to losing the full sun and dies in the winter months. It will begin to turn brown and drop leaves in an effort to get rid of any lower, inefficient leaves. The plant may then become spindly as it reaches for inadequate lighting. Make sure the plant is sitting in a sunny southern- or western-facing window for optimal indoor lighting. However, the lighting it receives indoors may simply not be enough to sustain it.

Proper Amount of Water

• Wait until the soil is dry to the touch before watering, then give a deep watering that eventually seeps out of the bottom of the pot. Check for blocked holes if no water appears; the roots may be rotting on the plant if they are standing in water. Avoid watering the leaves -- this can encourage powdery mildew. Use water that is room temperature; cold or hot water can shock the plant.

Soil Conditions

• If the rosemary has been in the same pot for some time, the soil may need to be changed to provide fresh nutrients to the plant. Indoor herbs need rich soil with good drainage; this prohibits water from sitting on the plant's roots to cause rotting. Use a commercial potting soil, but mix it with sand and peat moss in equal parts. Peat adds nutrients to the soil while assisting in drainage; sand can assist in drainage if it's a coarser grain. Therefore, avoid using fine-grained play sand, as that just weighs down the soil and can make it difficult for the rosemary roots to penetrate. Additionally, the potted rosemary will require additional nutrients normally obtainable in dirt. Herbs should be fed weekly when they are growing; if this has been neglected, try the manufacture-recommended amount of fish emulsion (organic) or an all-purpose liquid fertilizer.

Air Control

• The dry, stagnant indoor air in winter can also cause powdery mildew, which will do in the rosemary. Circulate air around the plant by running a small fan on a nearby table. Mist the plant lightly between waterings; while a heavy watering on the leaves can cause the mildew, a misting will not provide enough moisture for an infestation to start. Watch the air temperature, as well; rosemary prefers 65 to 70 degrees when indoors. Extreme changes, or constant excess hot or cold, may result in the plant's death.