10 Reasons Why Outdoor Plant Leaves Turn Yellow

Yellowing leaves on outdoor plants is a common issue that most gardeners will encounter at some point. While there are various causes, yellow leaves are often a sign that something is wrong and the plant is under stress. Addressing yellow leaves promptly can help get your plants back to health.

Here are the top 10 most common reasons why plant leaves turn yellow outdoors, and what you can do about it.

Overwatering

One of the most common causes of yellowing leaves is overwatering your plants. When the soil stays soggy for too long, it prevents roots from getting enough oxygen. This stresses the plant and causes the leaves to turn yellow.

Solutions:

Check soil moisture before watering. Only water when top inch of soil is dry.
Improve drainage by amending soil with compost or perlite.
Plant in containers with drainage holes to prevent waterlogging.
Allow soil to dry out between waterings.
Water less frequently but more thoroughly when you do water.
Consider using drip irrigation or soaker hoses to better control watering.

Underwatering

While overwatering is common, the opposite – underwatering – can also cause yellowing leaves. When plants don’t get enough moisture, they become stressed. Leaves first turn yellow then brown and dry out.

Solutions:

Check soil moisture before watering and water when top few inches are dry.
Water deeply and thoroughly – just damp surface soil is not enough.
Use mulch to help retain soil moisture longer.
Group plants with similar watering needs.
Consider installing drip irrigation on a timer to ensure consistent watering.
Move plants out of excessively hot, dry locations. Provide afternoon shade if possible.

Poor Drainage

Excess moisture and poor drainage go hand in hand. Yellow leaves often appear when roots are deprived of oxygen due to saturated soil. Heavy, compacted, clay-like soil is prone to drainage issues.

Solutions:

Amend soil with organic material – compost, peat moss, leaf mold etc to improve drainage.
Create raised planting beds to improve drainage.
Plant in containers with drainage holes.
Install French drains or drainage tiles to move water away from planting areas.
Aerate compacted soil with a core aerator.

Nutrient Deficiencies

Lack of important nutrients, like nitrogen and iron, is a common reason for yellow leaves in outdoor plants. Soils can be naturally lacking in nutrients or they get depleted over time.

Solutions:

Test your soil and add organic fertilizer or specific amendments as needed.
Work compost into soil annually to replenish nutrients.
Foliar feed plants showing deficiency symptoms with liquid fertilizer or compost tea.
Mulch plants annually with compost or nutrient rich material.
For container plants, fertilize regularly over the growing season.

Iron Chlorosis

Yellow leaves with green veins point specifically to iron deficiency or iron chlorosis. This is common in alkaline soils when iron gets locked up and unavailable to plants.

Solutions:

Apply chelated iron supplement as a foliar spray per label instructions.
Amend soil with iron-rich material – coffee grounds, compost, manure.
For potted plants, use iron-fortified plant food.
Consider using an iron supplement in your watering can when watering affected plants.
Grow iron-loving plants in acidic potting mixes.
Increase acidity of soil around affected plants.

Sunscorch

Intense sun and heat can scorch leaves, causing yellowing, browning, or spotting. When light levels or temperatures rise rapidly, sensitive plants can be damaged.

Solutions:

Provide shade for plants struggling in intense sun. Install shade cloth canopy if needed.
Plant in locations with appropriate light levels for the variety.
Allow plants to acclimate to increasing light levels in spring before situating in full sun locations.
Water plants well, especially during heat spells. Dry soil exacerbates problems.
Use reflective mulch to cool soil and minimize water loss.
Whitewash greenhouses and cold frames to reduce interior temperatures.

Cold Damage

Chilly spring or fall temperatures can also damage tender new growth, causing yellowing. Cold injury can occur even if temps are just slightly below freezing.

Solutions:

Cover sensitive plants overnight if frost is predicted. Use cloches, cold frames, or fabric covers.
Avoid trimming or pruning tender new growth late in day when cold nights are expected.
Plant susceptible plants in protected microclimates – against buildings, under trees or shrubs.
Delay planting out tender seedlings until past final frost date.
Select cold hardy plants varieties suitable for your climate.

Root Damage

Physical injury to plant roots from cultivation, insects, diseases, or cracking in dry soil can all cause yellowing leaves. Damaged roots cannot take up water and nutrients effectively.

Solutions:

Cultivate gently around shallow rooted plants. Never hoe deeply near plants.
Rule out root pests like root weevils or root rot diseases.
Prevent soil cracking by mulching and providing supplemental water in dry periods.
Correct overly compacted soil by double digging or amending with organic material.
Transplant stressed plants to loosen bound root balls. Prune damaged roots before replanting.

Leaf Miners and Other Pests

Leaf mining insects like leaf miners create meandering tunnels in foliage as they feed. This destroys leaf tissues and causes yellow spots. Other sucking insects can also cause yellow stippling.

Solutions:

Identify the pest culprit and apply appropriate organic pest control.
Remove and destroy heavily infested leaves.
Cover plants with floating row cover fabric to exclude pests.
Use sticky traps to monitor and reduce insects like whiteflies.
Attract beneficial insects by planting pollinator friendly flowers.
Maintain plant health and vigor to withstand pest pressures better.

Age-Related Decline

As plants mature or reach the end of their natural life cycle, yellowing leaves, stunted growth, and decline are common. Biennials and some perennials are programmed to fade after 2-3 years as they prepare to set seed.

Solutions:

Grow annuals and biennials from seed each year for best health.
Cut back leggy perennials like lavender and sage substantially in spring.
Divide congested clumps of perennials like daylilies every few years.
Replace aging shrubs and trees or prune rejuvenate overgrown specimens.
Provide optimal growing conditions with regular fertilizing, pruning, and diligent watering.
Propagate new container plants from cuttings to start fresh stock as older plants decline.

Environmental Pollution

Air pollution, road salt, deicing chemicals, herbicides, and other environmental contaminants can also cause leaf yellowing in outdoor plants. Foliage effectively filters toxins from the air and soil.

Solutions:

Wash leaves with water periodically to remove surface pollutants. Avoid overhead watering.
Plant in location away from roadways if possible. Use hedges or fences to screen plants.
Grow plants in containers with clean potting mixes indoors if outdoor pollution is problematic.
Use organic lawn and garden products to prevent chemical damage.
Install plants tolerant of pollution, salt exposure, and other urban stresses when growing in cities.

Fix Yellow Leaves and Get Plants Thriving Again

Now that you know the range of potential causes for yellowing leaves in outdoor plants, you can start troubleshooting! Check your care regimen, environment and the plant itself to pinpoint the issue. Address any problems promptly to restore plant health. With the right modifications, your landscape can be green again and flourishing in no time.

When is leaf yellowing normal?

While yellow foliage is often an alarm bell, some autumn leaf color change is natural and expected. Deciduous trees and shrubs undergo hormonal changes in fall that cause their leaves to turn hues of yellow, orange and red before dropping. Enjoy this seasonal spectacle as a prelude to winter dormancy.

Evergreens also routinely shed some interior needles and leaves to remain healthy. This gradual process is accelerated during drought or seasonal dormancy. As long as it does not defoliate more than 1/3 of the plant, some yellowing is normal.

How can I prevent leaf yellowing?

The best way to avoid yellow leaves is to provide consistent and proper care to keep plants in optimal health. Be diligent about:

Watering correctly – neither too much nor too little
Amending and fertilizing soils appropriately
Pruning regularly to stimulate new growth
Monitoring for pests and treating early
Managing environmental stresses by providing shade, wind protection etc.

Healthy, vigorous plants can better withstand and outgrow minor leaf yellowing with suitable adjustments to their care.

When to seek help for yellow leaves?

While many cases of yellowing foliage are manageable with attentive home care, it’s best to enlist professional help if:

The symptoms are severe and rapidly worsening
Multiple treatments have failed to correct the issue
There are no obvious underlying causes like drought stress or pests
Other symptoms like stunted growth, leaf spots or branch dieback accompany yellowing
The yellowing is isolated to just one plant among healthy neighbors

Consult with your local extension office, a horticulturist, or licensed arborist to diagnose unusual yellowing issues accurately. They can test soil, take foliar samples, analyze roots and provide suitable solutions.

Can yellow leaves become green again?

It depends on the severity of the underlying problem. Mild, temporary stresses like drought can be reversed and the foliage can re-green once conditions improve. However, prolonged or extreme stresses usually cause permanent damage. Severely yellowed leaves will typically drop from the plant. But if only a portion of the leaves are yellow, the plant may produce new green foliage, especially if the causal factors are mitigated.

When to remove yellow leaves?

Dry, crispy yellow leaves that are clearly dead are best pruned off. They will not recover.
Yellow leaves that are still somewhat pliable can potentially re-green and recover. Leave these be.
Remove faded leaves promptly from plants prone to fungal diseases to avoid infectious spores.
Eliminate yellow leaves infested with pests so they don’t spread.
Pick off selected yellowed leaves to improve appearance but don’t overprune.
Allow yellowing interior leaves on dense evergreen shrubs to self-shed. Avoid shearing these.

What to do with pulled yellow leaves?

Most yellowed leaves can be composted or added to a leaf mold bin after removal. Avoid composting diseased foliage – dispose of this with household waste instead. Use pulled yellow leaves as mulch beneath outdoor plants. Add foliage to the green bins in municipal composting programs. Just don’t let diseased leaves remain on the ground below plants. Discard pest-infested leaves in sealed bags with other non-compostables.

Conclusion

Yellowing leaves are a common gardening challenge. But armed with the knowledge of why plants suffer foliage yellowing and what you can do about it, you can get your landscape looking lush again. Proper diagnosis and quick corrective care are key. With attentive watering, occasional fertilizing, pest monitoring and other best practices, you can keep your plants in peak form with minimal yellowing.

Frequently Asked Questions

What causes yellow leaves on indoor plants?

Common reasons for houseplant leaves turning yellow are overwatering, low humidity, too much light, nutrient deficiencies, pests, and age-related decline. Adjust care, humidity and location to prevent and correct yellowing.

How can I make yellow leaves green again?

Mild cases of yellowing may recover with improved growing conditions. Boost nutrition, adjust watering, modify environmental factors and address pests. But severely yellowed leaves rarely return to green and will eventually drop off. The plant may grow new green leaves when healthier.

What makes palm leaves turn yellow?

Yellowing palms are often stressed by overwatering, low nutrient levels, or salty irrigation water. Allow soil to dry between waterings, apply controlled-release palm fertilizer, and use non-salty water to prevent/correct yellow fronds.

Why are my plant’s leaf tips turning yellow?

Yellow leaf tips are often caused by dry air or tap water containing chlorine and fluoride. Mist plants regularly, use filtered water, and keep foliage clean to prevent/reduce tip burn. Ensure proper nutrition and watering as well.

What causes yellow spots on plant leaves?

Yellow spots can be caused by fungal leaf spots, bacterial infections, sunscald damage, mineral deficiencies, spider mite feeding, or herbicide injury. Identify the cause and address appropriately. Remove badly affected leaves promptly.

How do I know if yellow leaves are natural?

Deciduous trees and shrubs normally turn yellow in fall. Evergreen inner leaves yellowing incrementally is also natural. If leaf color change occurs at the expected time and is evenly distributed, it is likely just seasonal. New foliage growth indicates health.

Why are my tomato plant leaves turning yellow?

Tomatoes get yellow leaves from overwatering, under feeding, physiological leaf roll, early blight fungus, tobacco mosaic virus, age, or root-knot nematodes. Identify cause and adjust care accordingly. Provide ample nutrition and monitor moisture levels.

How can I revive a plant with yellow leaves?

Assess growing conditions and address any issues found, like excess water, insufficient light, pH imbalance, disease, pests etc. Fertilize mildly if needed and prune back damaged tissue. The plant may recover over time with improved care if new growth appears.

What deficiencies cause yellowing leaves?

Nitrogen, magnesium, iron, manganese and zinc deficiencies commonly cause yellowing. Also pH imbalance reducing nutrient availability. Test soil and adjust pH to 6.5-7. Foliar feed plants showing symptoms and amend soil based on test results.

Should I cut off dead yellow leaves?

Removing dead yellow foliage can improve appearance and sanitation. But don’t overprune. Leave yellowing leaves that still feel supple, as they may recover. Discard diseased and pest-infested yellow leaves promptly. Compost clean pulled leaves.

Key Takeaways on Yellow Leaves in Outdoor Plants

Foliage turning yellow is a common gardening problem signaling plant stress.
Overwatering, under watering, poor drainage, mineral deficiencies, pests, diseases and environmental factors are common culprits.
Address causal factors promptly to restore plant health before yellowing worsens.
Improve soil conditions, spacing, watering habits and maintenance to prevent many cases of yellowing.
Severely damaged yellow leaves won’t recover. But new green growth indicates the plant is rebounding.
Monitor for patterns among specific plants or areas to determine causes. Keep detailed notes.
Enlist help from experts if yellowing persists despite your best efforts to treat it.
Maintain vigor with consistent care and yellowing will be less prevalent in the landscape.