Lily of the valley, Convallaria majalis, is a rhizomatous ground-covering perennial with sweetly fragrant bell-like white or pink blossoms that nod demurely among masses of elliptical green leaves.
Suited to cultivation in Zones 2 to 9, it prefers full to part shade and moist, fertile soil.
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Our guide to growing lily of the valley has all you need to know to grow it in your outdoor living space.
This article focuses on 13 reasons why the foliage may turn from green to yellow and what, if anything, to do about it.
Here’s the list:
13 Causes of Yellow Leaves on Lily of the Valley
1. Cultivated Variety
When green leaves turn yellow, it’s known as chlorosis, and as gardeners, we look into what may cause it, such as unfavorable environmental conditions or disease.
However, sometimes we can overlook more obvious reasons, like the possibility that the leaves aren’t supposed to be green.
In its natural Asian and European habitats, lily of the valley foliage is green.
But there are cultivated varieties with yellow and variegated leaves, like ‘Haldon Grange,’ which sports green leaves with yellow margins, and ‘Polish Beauty,’ that has green foliage with yellow stripes.
That’s not to say that cultivated varieties can’t also become chlorotic, but that it’s a logical place to begin an investigation of unexpected coloration.
2. Excess Fertilizer
Lily of the valley is not a heavy feeder and doesn’t need more than a top dressing of compost in early spring.
If you use a product with a high nitrogen content, you may find the leaves start to turn yellow.
In addition, the lily of the valley may also produce an abundance of foliage and few flowers.
It’s worth noting that even if you don’t fertilize your lily of the valley directly, it’s still possible to expose them to excess nitrogen.
The source? Lawn runoff.
Since nitrogen supports lush foliar growth, lawn fertilizers are nitrogen-rich.
Avoid fertilizing the lawn during bloom time and consider placing landscape edging along the garden to separate it from the grass.
3. Moisture Stress
Both over- and underwatering can cause moisture stress that appears as yellow leaves.
Signs of oversaturation include wet soil and a slimy feel to the foliage, whereas dry ground and crisp leaf tips signal insufficient moisture.
To inhibit moisture stress make sure you grow your lily of the valley in well-draining soil and provide consistent moisture by watering weekly in the absence of rain.
4. Natural Decline
At season’s end, the foliage turns yellow and orange-red fruits appear before the plant dies back to the ground. This is not a sign of distress, but the normal aging process.
It’s best to allow the foliage to decline naturally rather than mow it down because it continues to produce chlorophyll well after the plant has finished blooming, supporting root health and storing the energy needed for next year’s flowers.
5. Nutrient Deficiency
The inability to absorb appropriate nutrients from the soil can cause foliar irregularities.
When cultivated in organically-rich loam, rest assured that your lily of the valley plants will have what they need to thrive.
Lily of the valley will tolerate poor soil, but its performance may suffer unless the earth is amended with organic matter, like compost, humus, leaf mold, or peat to provide essential nutrients, and horticultural sand for excellent drainage.
If you are growing your plants in an area where you suspect the soil isn’t suitable, it’s best to do a soil test and amend accordingly.
6. Overcrowding
Plants that are too close together may discolor and decline as a result of competition for moisture and nutrients.
The mature dimensions of lily of the valley are six to 12 inches tall and nine to 12 inches wide. When planting, space adequately to accommodate the spread.
Evaluate the gardening space annually to monitor for overcrowding.
If your spring display lacks vibrancy and plants are dense, divide them in early spring or early fall to reduce the volume.
You can learn more about how to divide lily of the valley here.
7. Overexposure
Lily of the valley prefers to grow in full to part shade. When exposed to too much sun, the foliage will be pale verging on yellow instead of lush green.
Hot temperatures and dryness can compound the stress, turning leaves from yellow to brown.
While many, if not most, flowering plants favor sunshine, lily of the valley does not. It’s a woodland species accustomed to thriving in the dappled and dim light beneath trees.
For many, myself included, the deciduous leaves are not yet out during bloom time.
Keep this in mind when planting and select placements shaded by evergreens and structures to avoid overexposure.
8. Pathogens
Fungal pathogens can cause different types of chlorosis.
Gloeosporium fungi cause a disease called Anthracnose. Symptoms are water-soaked lesions and yellowing foliage.
Aureobasidium microstictum fungi are responsible for leaf streak with water-soaked lesions, brown streaking, and yellow halos.
And Puccinia sessilis rust fungus leaves yellow spotting on the upper sides of the foliage.
Unfortunately, inhibiting a proliferation of moisture-loving pathogens on damp-loving shade plants is challenging.
Grow in well-draining soil, avoid overwatering, and when you do water, make sure you do so at soil level rather than soaking the foliage.
These practices will go a long way toward disease prevention.
You can apply organic fungicidal neem oil preventatively and during an outbreak to inhibit fungal development.
9. Pests
In addition to disease, some pests may cause leaf discoloration.
Foliar nematodes, Aphelenchoides spp., feed on the leaves, causing the tissue between the veins to become chlorotic.
There are few effective treatments, so you’d need to dig up and destroy affected plants in the event of an outbreak.
Preventative measures include sanitary garden practices and not watering over the leaves.
Slugs and snails are notorious night feeders that thrive in dark, moist surroundings. Hand picking or deterrent traps may reduce populations.
When in doubt about the presence of pathogens and pests, you can contact your local agricultural extension for advice.
10. Planting Too Deeply
Sow rhizomes shallowly, with the rootstock barely covered with soil. Setting them high helps to inhibit rotting in the perpetually moist soil they thrive in.
Planted too deeply, the rhizomes and roots can end up rotting underground.
Soft yellow leaves and wilting may be signs of rotting roots below the soil.
If they are dark, malodorous, and mushy when unearthed, discard them in the trash.
Cut healthy, firm, light-colored rootstock away from rotten portions, rinse them, and replant as desired.
11. Poor Drainage
As mentioned, oversaturation will cause the rhizomes to rot underneath the soil.
In addition to more obvious causes like overwatering, improper drainage is one cause of ponding water.
If the soil has become compacted, even normal amounts of moisture can have trouble percolating.
If you have compacted soil you can dig and lift the rootstock in spring or early fall and amend with horticultural sand to facilitate drainage. Replant immediately.
12. Soil pH
Lily of the valley grows best in organically-rich soil with a pH of 6.0 to 6.5.
If the soil is overly acidic or alkaline, the availability of macro and micronutrients changes.
Some may become present at toxic levels, while others may become less available. Both extremes have the potential to impair chlorophyll production and result in chlorosis.
Conduct a soil test before planting to determine your garden’s pH.
Follow the recommendations you receive, such as amending with peat moss to increase acidity or lime to increase alkalinity, to achieve the appropriate range.
13. Weather Extremes
Finally, flora may respond adversely to drastic temperature fluctuations, such as a late spring blizzard or heatwave. Stress may manifest as leaf discoloration or wilting.
If an unusual cold snap is in the forecast, loosely cover emerging foliage with two to three inches of fresh, dry straw mulch.
Carefully remove it as soon as possible when the weather warms up.
Provide supplemental water if the top few inches of garden soil are dry in advance of a predicted hot spell. Water early in the day to minimize evaporation.
Monitor the moisture daily using a moisture meter and supplement as needed until the weather returns to normal. Take care to avoid oversaturation, especially in poorly drained settings.
Banish the Yellow
Lily of the valley foliage should be a robust shade of green unless you have a cultivated variety bred for a buttery hue or it’s the end of the growing season and the leaves are fading.
It’s time to evaluate your plants and take action where necessary to banish the yellow for a festive and fragrant spring display.
Have you dealt with yellow foliage on your lily of the valley? Please share your tips in the comments section below.
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