March 28, 2024 6:29 AM
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Causes for Yellow Leaves on Houseplants – Ken Lain

A thought as we charge through the New Year. Gardening helps us reconnect with the earth and ourselves. Personal growth is easier if we grow plants. We accomplish new growth when blessed with health, ambition, wits, and persistence. Each we possess is a gift. It’s at the root of why trees have universal appeal and gives comfort to just about everybody, no matter their age, the language we speak, or the country we live. Plants are important.

Yellow leaves on your houseplants are concerning, and caused by several conditions. Sometimes the cause is apparent, so you can diagnose and fix it immediately. There are other times when the problem is mysterious. In these cases, you’ll need to change one thing at a time until you see improvement in your plant.

Growing plants is always a matter of patience. Do your best to eliminate these common reasons for yellowing leaves, then wait to see what happens. Even after you correct the problem, it’s still likely the yellow leaves will drop. As your plants’ health improves, new leaves will grow once again.

Moisture Stress

Over and under water is the number one problem when a plant’s leaves turn yellow. Only water plants as much as the plant needs. Easy to say, right? A good moisture meter takes a lot of this guesswork out and is a must for serious gardeners.

Plants not receiving enough water drop leaves to prevent transpiration, so they conserve water. The leaves typically turn yellow before falling. If your soil is dry and this is happening, deeply soak the plant on a regular schedule.

Too much water can be just as damaging. When the soil doesn’t drain well, the soil is waterlogged, and roots drown. Without oxygen, roots start to die, causing leaves to turn yellow and drop.

Normal Aging

As plants age, the lower leaves turn yellow and drop off naturally. This is simply a regular part of their growth. In this case, don’t worry. If the plant becomes too leggy, consider trimming the main stem to promote new growth and business.

Cold Damage

Tropical plants do not like to be cold. Cold drafts cause the leaves to turn yellow and drop. Short periods of exposure to intense cold are even worse, causing outright browning on the foliage or pale, transparent spots to appear between the veins.

If your plant is near an air-conditioner vent in summer or a drafty window in winter, move it to a less frenzied spot. Keep an eye on it to see if the yellow leaves spread further. It is a good idea to mist houseplants overwintering with you to increase their humidity.

Lack of Light

Plants that receive too little light yellow on their lower leaves before dropping. This is especially true after the short days of winter. If this is your issue, there is a clue.

Houseplants showing signs of light stress are typically yellow on the side away from the light source. The leaves near the window take all the light and then starves the leaves on the opposite side.

Move your plant to a sunnier location and see how it fares. Your plants might need supplemental full-spectrum daylight bulbs until spring days become longer.

Nutrient Deficiency

Leaves turn yellow if a plant does not receive its required nutrients. This can be caused by too much calcium in the water if you’re using hard/alkaline water or by a nitrogen deficiency.

Symptom – the plant’s top leaves are yellow first. An unusual yellow pattern occurs. The veins may remain dark while the tissue between fades and turns yellow.

Pickier plants like orchids need different foods than others. The nutrients required vary based on the species. Pick a well-balanced houseplant food and use it regularly. My favorite is Watters ‘Root & Grow‘ used at half strength every time a plant is watered. You will be amazed at the results.

Viral Infection

Yellow is often accompanied by deformed leaves, stems, and discolored flowers. Look for blotchy spots that spread yellow patched through the leaves. Pinch infected leaves and stems from the plant right away.  Spray the entire plant with Watters ‘Copper Fungicide.’ If the yellow leaves continue, discard the plant.

This is dangerous and can kill your plant.  Viral plant infections cannot be cured and can infect all susceptible plants nearby. While it may be painful if it is a favorite, discard any plants you suspect are infected. Wash and sterilize any pruning tools or pots before using them on other plants.

Until next issue, I’ll be helping local’s grow better houseplants here at Watters Garden Center.

Ken Lain can be found at Watters Garden Center, 1815 Iron Springs Rd in Prescott, or contacted through his website at WattersGardenCenter.com or Top10Houseplants.com.

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