Growing orchids is challenging with more than 30,000 species and 1,000,000 hybrids from which to choose. All tropical orchids need good air circulation, neutral water and fast-draining potting soil. Other requirements, such as light and temperature, vary depending on the type of orchid. Brown leaves can be caused by fertilisation problems, watering problems, or problems with lighting or temperature.
Brown tips on the leaves indicate that your plant is receiving too much fertiliser. Some growers say that orchids don't need any fertiliser at all since they get their nutrients from compost and water, but many growers use some fertiliser. The amount used depends on your orchid's growing medium. Use a complete fertiliser with a 1-1-1 ratio if you're growing orchids in tree fern, osmunda, peat, charcoal or stone. Use a 3-1-1 fertiliser for orchids grown in bark.
Orchid leaves turn brown if the plant isn't receiving enough water. In addition, the leaves may wilt or become flattened, and the veins might stand out. The leaf may also split down the middle or the edges of the leaves may curl under. How often you need to water depends on what medium your orchid is planted in, the location of the pot, how shady it is, pot size and type and how much air circulation your plant receives. Plants grown in small pots or in porous clay pots dry out faster than plants grown in large pots or plastic pots. Don't water your orchid until the surface of the medium is dry, then water until you can see water draining from the bottom of the pot. Use low-chlorine, low-mineral content water like rainwater.
Light and temperature
Too much light causes dark brown splotches on the leaves. These brown splotches are burns. Provide your orchid with filtered light, and use a fan to prevent heat build up. Increasing the humidity also helps. Most orchids require partial shade to flower and grow well. Consider temperature. Orchid leaves burn and turn brown if a plant is subjected to temperatures of 43 degrees for two hours or 49 degrees for 10 minutes. Although very rare, these temperatures can occur in greenhouses during the summer.
Low humidity causes leaves to wilt and the tips to turn brown. Orchids need 50 to 80 per cent humidity to thrive. Brown spots on leaves can also indicate your water's iron content is too high. Use deionised water to flush the extra iron, and then water with bottled water or rainwater. Brown spots that turn black mean your orchid has a fungal infection. Lower the humidity, dry off the leaves and apply a fungicide.