Orchid stems and foliage may not be the most engaging parts of the plant, but they usually are the first parts that indicate an orchid is in distress. And orchid stem that turns yellow is experiencing chlorosis, which is a condition that causes plant parts to lose their healthy green color and turn yellow. In human terms, think of your orchid as turning pale. Somethings is amiss.
It's normal for older leaves and flower spikes to turn yellow before they dry to brown and fall off. Reddish stems on some varieties are also a natural occurrence. But when your orchid stem starts to turn yellow it's time to take corrective measures now before the underlying cause gets worse.
Yellowing stems result from overwatering, too much sun, infection, and poor nutrition. Early steps to remedy the cause can prevent it from deteriorating further, turning brown or black and eventually dying.
What Is an Orchid Stem?
The orchid stem is the base of the plant where the leaves and flower spikes grow from. Sometimes the part of the plant that produces flowers (the spikes) is erroneously called the stem, but the spikes die back naturally when flowering is complete. A healthy main stem enables photosynthesis and supports growth of the entire orchid.
Overwatering is an underlying cause of many orchid problems including yellowing stems. It's important to keep roots well hydrated but watering too often or allowing the pot to sit in water can saturate the roots and advance excess moisture up into the stem. Water displaces oxygen causing the stem to lose healthy green tissue.
If you suspect overwatering, remove the orchid from its pot and inspect the roots. White, mushy roots indicate it's getting more water than it can absorb. Use a sterile cutting tool to remove roots that have lost all turgidity and repot the orchid with fresh, dry, potting material. Give it time to recover. Withhold water for several days and then reduce water and humidity until the stem starts to regain healthy green color. This may take several days to several weeks.
Too Much Sun
Different orchids thrive best in varying degrees of sunlight, but the type of light almost always needs to be indirect. Exposure to sun hitting the plant directly can adversely affect the amount of chlorophyll, resulting in a chlorotic, yellowish stem. Heat generated by direct sunlight may also cause insufficient moisture.
Water the orchid thoroughly and allow excess to drain. Then move it to a cooler location with indirect light. Withhold fertilizer until the stem regains green color.
Unless you have a greenhouse, you are probably growing an orchid as part of a houseplant collection. This often means keeping the plant in a pot with a soilless medium made up of combinations of bark, sand, moss, and perlite. Orchid potting mixes can support nutrition but provide very little actual food. This makes supplemental feeding (fertilizing) important and necessary.
Nutrition deficiencies develop when the plant gets either too much calcium or not enough nitrogen. Hard water raises calcium levels and nitrogen is the element that supports healthy green foliage. Early signs of nutrient deficiency include stunted growth, failure to bloom and patterns of yellow or dark spots on leaves.
If your orchid has been in its same pot for more than a year, repot with fresh planting medium. If you do not fertilize on a regular schedule, start by using a 1/2 dilution of fertilizer specifically formulated for orchids. Commercial fertilizers contain salts which can damage sensitive orchid roots. Use filtered or distilled water or let tap water sit out for several days before using it. Fertilize monthly until you see new, healthy green growth. Fertilizing can be increased to bi-weekly once the orchid is actively growing.
Fungal and Bacterial Infection
Infections causing chlorosis in your orchid are the most difficult to correct. This makes prevention the best treatment. Bacteria and fungi can affect any part of the orchid from roots to leaves and once the main stem starts to turn yellow, the infection has advanced beyond early stages.
Immediately isolate the plant. Remove it from the pot and inspect the roots, removing any that appear black or mushy. Random yellowing or dark spots on leaves can also indicate infection. Severely damaged leaves can be pruned, but take care when removing them from a monopodial, single-stemmed orchid such as Phalaenopsis. Removing multiple leaves can damage the plant beyond saving. Treat all cuts with hydrogen peroxide.
Allow the plant to recover. If the stem on a single-stemmed orchid continues to deteriorate and turn black, the orchid should be discarded.
Should I cut out a yellow stem?
Stems on monopodial, single-stemmed orchids should not be cut off. This can lead to irreversible damage which the orchid cannot survive. If your orchid has pseudobulbs that turn yellow, the plant part may have reached the end of active growth and can be removed at the base.
Does a yellow stem mean my orchid is dying?
A yellow stem does not always mean that an orchid is dying. A flower spike, sometimes called a “stem,” turns yellow and falls off naturally. When a main stem turns yellow, the orchid is suffering from a condition called chlorosis, which often can be corrected.
How do I know if I've overwatered my orchid?
The easiest way to tell if you’ve overwatered an orchid is to remove the orchid from its pot and check the roots. If they aren't plump or feel mushy, the plant is getting too much water. Early signs include limp foliage, and soft tissue at the base of the stem.
Chlorosis. Royal Horticultural Society