Life

Why Are My Plants Turning Yellow? 7 Common Causes and Solutions

Do you wander around your garden dismayed by yellowing leaves on your plants? Has your beautiful green houseplant started looking a little peaky with odd yellow spots?

Yellowing leaves are a common gardening problem faced by both novice and expert gardeners alike. But don't panic - yellow leaves don't necessarily spell disaster for your plants. The key is identifying why the leaves turned yellow in the first place.

In this comprehensive guide, we'll explore the 7 most common reasons behind yellow plant leaves and how to fix them. Read on to get your plants back to their former green glory.

Reason 1: Improper Watering

One of the most prevalent causes of yellowing leaves is improper watering. Both overwatering and underwatering can cause leaves to turn yellow.

If you've been giving your plants lots of water but the soil stays soggy for days, you're likely overwatering. Constant moisture prevents the plant roots from getting oxygen. It also leads to fungal root rot diseases that damage the roots and cause outer leaves to turn yellow and drop.

Underwatering has the opposite effect - the soil dries out and the plant can't take up enough moisture and nutrients to support new growth. This leads to dry, shriveled yellow leaves, especially in the older outer leaves.

How to Fix It

  • Check the soil moisture before watering - stick your finger in the soil and if the top inch is dry then it's time to water.

  • Adjust your watering schedule and volume - cut back on watering plants showing signs of overwatering and increase water for underwatered plants.

  • Water thoroughly until water drains from the bottom of the pot, then don't water again until the top inch of soil is dry.

  • For outdoor plants, install drip irrigation on a timer to ensure consistent watering.

Reason 2: Poor Drainage

While all plants need water, they also need oxygen around their roots. Soil that is constantly wet from poor drainage prevents air from reaching the roots.

If your plants are planted in heavy, dense soil or you don't have drainage holes in the bottom of the planter, excess water can't drain away after watering. This lack of oxygen damages roots and causes yellowing leaves.

How to Fix It

  • Repot your plants in a potting mix formulated for better drainage. Look for mixes with peat moss, perlite, coco coir, or bark chips.

  • Create drainage holes in planters - use a power drill with a 1/4 inch bit to add several holes in the bottom of the planter.

  • Improve drainage in garden beds by mixing in compost or small gravel to loosen dense soil.

Reason 3: Sunlight Issues

Plants need the right amount of sunlight for their variety. Too much harsh direct sun can scorch and yellow leaves, while too little sunlight causes slow growth and pale yellowing.

Leaf scorch shows up as yellow or brown crispy edges and tips of leaves. It happens when the sunlight intensity is too strong for that plant. Shade-loving plants like ferns are very prone to leaf scorch if placed in direct sun.

Insufficient sunlight shows up as light green or yellowish leaves all over the plant. Weak leggy growth may also occur as the plant strains to reach for the sun. This happens to sun-loving plants like tomatoes when grown in too much shade.

How to Fix It

  • For scorched leaves, move the plant to a shadier location protected from intense afternoon sun. Filter the sunlight with a sheer curtain.

  • If the plant needs more sun, move it slowly into brighter light for a few hours a day until it can tolerate full sun without scorching.

  • Rotate indoor plants periodically so all sides get sunlight.

  • Supplement outdoor light with grow lights if the location can't be changed.

Reason 4: Low Nutrients

A lack of essential nutrients in the soil is a very common reason for yellowing leaves. Nutrients like nitrogen, iron, and magnesium are vital for chlorophyll production and new growth.

Without enough of these nutrients, the lower leaves start turning uniformly yellow first as the plant moves nutrients from old leaves to new leaves. Eventually the yellowing spreads if more nutrients aren't provided.

How to Fix It

  • Test your soil pH and adjust it to your plant's preferred range. Most nutrients are best absorbed in the 6.0 to 7.0 pH range.

  • Mix a balanced fertilizer into the soil prior to planting and apply per instructions during the growing season.

  • For container plants, apply a water-soluble fertilizer every 2-4 weeks.

  • Top-dress containers with worm castings or compost which slowly release nutrients.

  • For yellowing between leaf veins, use a foliar spray with iron, magnesium, and manganese.

  • Increase organic matter by adding aged compost, manure, or leaf mold annually.

Reason 5: Cold Weather

Just like humans, plants don't appreciate sudden temperature drops and chilly weather. Some plants are more cold-sensitive than others.

Cool fall and winter temperatures can cause leaf yellowing and leaf drop. Tropical plants have an especially hard time handling temperatures below 50°F.

Frost damage also initially appears as areas of yellow, dried out tissue on leaves. After frost, leaves turn mushy and black.

How to Fix It

  • Move potted tropical plants indoors before temperatures drop in fall.

  • Protect semi-hardy plants by moving them into a greenhouse or bright window.

  • Cover sensitive outdoor plants with fabric row covers overnight when frost is expected.

  • Don't prune or fertilize plants in fall so they harden off for winter dormancy.

  • Wait until spring to prune out dead leaves and stems. Fertilize when new growth resumes.

Reason 6: Root Bound Plants

As houseplants or garden perennials grow over time, their roots fill up the container or space in the garden bed. Once the roots are crowded and tangled, they can't take up nutrients efficiently.

The lack of nutrients shows up as yellow lower leaves. You may also notice stunted growth. Root bound plants need more frequent watering as their limited roots can't absorb enough.

How to Fix It

  • Carefully remove the plant from its pot and loosen any circling roots. Prune any diseased roots.

  • Repot in the next larger pot size, with fresh potting soil.

  • For in-ground plants, either divide congested perennials or dig up, prune roots, and replant.

  • Water well after repotting, then let the soil partially dry out before watering again while new roots form.

Reason 7: Pests or Diseases

Sometimes yellow leaves are caused not by growing conditions or nutrients, but by outside influences - pests and diseases.

Fungal diseases, bacteria, viruses, and insects can all lead to yellowing. The yellowing may be scattered in patches across the leaves or concentrated just at the leaf veins or edges.

Identify the culprit - common ones are downy and powdery mildew, aphids, whiteflies, and tomato wilt diseases. Catch infestations early before they spread.

How to Fix It

  • Remove diseased leaves immediately and throw in the trash. Don’t compost them.

  • Apply organic fungicides like neem oil to protect healthy plants from infection.

  • Wipe leaves with a damp cloth to control small infestations of aphids and mites.

  • Apply insecticidal soap or neem oil as needed for larger pest problems.

  • Rotate plantings to different beds each year to prevent disease carryover in the soil.

Conclusion

I hope identifying the reasons behind your yellow plant leaves helps you get them back to vibrant good health. Armed with this knowledge, you can carry out the proper solutions for any type of yellowing that appears.

While sometimes disheartening, yellow leaves are rarely fatal and are easy to correct. Proper ongoing care is key to preventing most causes of yellowing leaves.

Be sure to monitor your plants closely for early signs of pests, diseases, underwatering, and nutritional deficiencies. Catching issues early makes correction much simpler.

With a little time and TLC, your plants will be back to their beautiful green selves, giving you seasons of enjoyment in your garden and home.

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