11 Reasons Your Gardenia Has Yellow Leaves
There are many reasons your gardenia plant may have yellow leaves. Many issues that cause this problem can be resolved if promptly addressed. In this article, gardening expert Melissa Strauss shares the most common reasons this happens, and how to fix it when it does!
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Who doesn’t love the creamy, redolent, and embracing fragrance of an alabaster gardenia blossom on a sultry summer evening? Gardenias stand up very well to the steamy heat of a Florida summer, and some varieties can survive winters as far as zone 6.
They are not especially vulnerable to pests and disease. But if you notice yellow leaves on your gardenia, it can signify that something is off.
Despite their seeming hardiness when planted in an ideal environment, these shrubs can be very intolerant of several factors. Gardenias have specific preferences regarding water, nutrients, light, and soil. If any of these factors are out of balance, the foliage will tell us by turning yellow. Let’s explore some possible reasons why your gardenia has yellow leaves.
Natural Causes
Sometimes a gardenia loses its leaves because they are old and ready to die. This is particularly prevalent in the fall and winter, although it can happen at any time of the year.
If you notice the odd leaf here and there, particularly the older ones toward the bottom, turning yellow, don’t worry too much. If the issue doesn’t progress into the newer leaves or spread to a large area, it’s probably just nature running its course.
Overwatering
Gardenias are a bit picky about the amount of water they need and how they prefer their soil. While a few extra days of rain is not likely to do any real damage, if you are consistently overwatering or your rainy season has been extra rainy, you may run into this issue.
In general, gardenias need about one inch of water per week. If they get this much rainwater, they don’t need additional watering. A general yellowing of the bottom foliage, more than just a leaf here and there, might be a sign of overwatering.
The Fix
Suspend watering for a few weeks and see if the yellow leaves continue to spread. If this doesn’t work and the problem spreads, you could have a more severe issue. Overwatering can also cause root rot and can be the result of a drainage issue. These are trickier and more complicated issues.
Poor Drainage
Gardenias don’t like to have wet roots. They like moist soil but do not survive in marshy or swampy areas. Clay-heavy soil can also be an issue because it compacts and doesn’t allow water to drain correctly.
If you see symptoms of overwatering and amending your watering schedule doesn’t seem to be working, you may need to address the soil issue that could be causing yellow leaves on your gardenia.
The Fix
This is a bit more complicated as it requires some digging. If your plant is in a low-lying area, the best way to deal with this issue is to relocate it. Consistently trying to mitigate the damage by amending the soil and implementing soil drainage can run you ragged.
If the plant is young and hasn’t established a large root system, the best course of action is to dig it up and move it to higher ground. However, sometimes we do things to the landscape that changes the drainage in a space, and we end up with a mature plant with a drainage issue. In this case, it might be better to amend the soil.
The best way to amend the soil is to add lots of organic matter. Compacted soil is commonly at fault for poor drainage. It’s best to amend the soil before planting, naturally, but again, this isn’t always possible.
What you can do is watch where the water is coming from and amend the soil next to the plant in that direction. Mixing in materials like compost, manure, shredded bark, peat moss, and sand will make your soil fluffier, for lack of a better word. Fluffy soil allows water to pass through, which keeps it from pooling around the roots of your plant.
Root Problems
If the issue of too much water progresses, you may end up with the more severe issue of root rot. Root rot first manifests in gardenia as yellowing in the lower section of the shrub. As the roots rot, they can’t absorb the proper nutrients, and the leaves begin to die from the roots up.
If the yellowing of the bottom leaves progresses and the older leaves begin to turn brown and fall off, you could have an issue with root rot. Fungal pathogens, such as Phytophthora or Pythium, often cause root rot. These fungi thrive in areas of excess moisture, particularly during cooler weather.
The Fix
If the roots are not too far gone, it is usually possible to rescue a plant with root rot. You are likely to lose a lot of foliage in this process, and the plant may even go into shock and lose its leaves altogether. If this happens, don’t fret yet, just give it some time. They will probably grow back.
The best course of action is to dig up the plant and trim away any diseased roots, leaving as much healthy root tissue as possible.
Re-plant the gardenia in a new spot, with fresh soil that has good drainage, and water sparingly for a few weeks. Don’t water too deeply, as keeping these roots wet could lead to the spread of any fungus that is left in the remaining roots.
Underwatering
Just as too much water can be an issue for gardenias, so too can a lack of water. Underwatering will appear in the leaves farthest from the roots first, as the plant will not have enough water to transport to the outermost growth. These leaves will turn yellow, dry, and ultimately fall off.
The Fix
This one is pretty simple, an underwatered gardenia is far more resilient than an overwatered one. Gardenias need about an inch of water per week. In times of drought, it is important to give them a little extra water. Watering once per week is usually just fine for a mature gardenia. A newly planted gardenia should be watered more frequently.
If you live in a warmer climate, you may need to increase your watering during the hottest months. This can help protect the leaves a bit from burning. Sandy soil heats up faster than other soil types, so when it’s very hot, watering can help to cool, things down.
Soil pH is Too High
Research shows that gardenias prefer to be planted in slightly acidic soil (pH of 6.5 or lower). Without the proper acidity, the plant will suffer from nutrient deficiency, causing the leaves to turn yellow while maintaining green veining.
Certain minerals cannot break down in an alkaline environment, and the nutrients become unavailable to the plant. Fertilizing can be a temporary remedy if you use an acidic fertilizer, but it will not provide a long-term solution.
The Fix
Elemental sulfur is a good way to acidify your soil in a way that won’t damage the plant. The only issue is that changing the soil pH can take literally years. You must apply sulfur on a regular basis, or you will run into the same issue repeatedly.
While compost, pine mulch, and coffee grounds are claimed to naturally acidify your soil, these methods are generally ineffective as a long-term solution. However, they break down and add valuable organic material to your soil, plus mulches reduce moisture evaporation from the soil’s surface, so you should still use these as well!
Other Nutrient Deficiency
The underlying issue with all of the above problems is nutrient deficiency. Too much water can dilute or rinse out the nutrients in the soil, inhibiting the plant’s uptake of proper nutrients. Lack of water or soil that is too alkaline or acidic will also inhibit the breakdown of nutrients in the soil, making them less available to the plant.
The Fix
If all of the other measures don’t seem to be working, look to your fertilizing routine for answers to your yellowing leaves. Gardenias need a lot of iron and copper in addition to nitrogen, phosphorus, and potassium. If you’re not presently fertilizing your gardenia, get in the habit of giving it these nutrients on a regular basis.
Gardenias need to be fertilized during their growing seasons, which are spring and summer. Fertilizing encourages new growth and nourishes the existing foliage. Remember to give your plants a break from fertilizing in the fall and winter as off-season fertilizing will encourage new growth which is more vulnerable to freezing weather.
Overfertilizing
Gardenias have fairly significant nutrient needs, but overfertilizing is always a possibility. Too much fertilizer can burn your plant out. An overfertilized gardenia will have yellow leaves that turn brown around the edges. Brown patches may appear elsewhere on the foliage, and the leaves will drop.
The Fix
If you are concerned that you may have overwhelmed your gardenia with fertilizer, you can flush the soil with water. This will help to dissolve any large amounts of minerals in the soil. After this, avoid fertilizing for a few months and then resume fertilizing once per month during the growing season. Give them a break during the winter to avoid new growth that can be damaged by the cold.
It’s hard to overfertilize with organic granular fertilizers as these are meant to decompose into the soil and gradually release their nutrients over time. If you find yourself having difficulties gauging the fertilizer needs of your plant, consider switching to an organic dry fertilizer!
Not Enough Sun
If your gardenia has yellow leaves, is not producing flowers, or is growing very much, or the growth is sparse and leggy, it might need more sun. These plants need full sun in the morning to produce enough chlorophyll. If the shrub gets fewer than 6 hours of direct sun per day, it may suffer from a lack of light exposure.
The Fix
If you are able to relocate your plant to a location that receives plenty of sunlight early in the day, try your best to remove obstructions that are limiting the amount of sun it gets. Gardenias make great container plants, so if you don’t have a good location to put one in the ground, consider potting it so that you can move it around easily.
Excessive Sun
As much as these flowers need lots of morning sun, too much sun in the afternoon can cause the foliage to scorch and blooms to fade quickly. If your shrub is getting a lot of direct sun in the afternoon, you may notice its leaves fading and the blooms turning yellow and dying quickly.
The Fix
If relocating is a possibility, you can always fix this issue by moving it to a spot that has some protection from the sun later in the day. If it is impossible to move the gardenia, another potential solution is to plant something larger to block some of the afternoon sun. Putting up temporary shade cloth in the peak of summer may also help retard some of the direct UV exposure the plant receives.
Cold Weather
Gardenias are surprisingly cold tolerant, but prolonged periods of weather below freezing temperatures can cause damage to the foliage, as can freezing winds. You might not even know this is happening until after the fact.
I live in North Florida, and I will say this: during the great freeze of December 2022, I lost a lot of plants. However, all three of my gardenias looked green and healthy, even after four nights of temperatures below 30°F uncovered.
My ‘Frostproof Gardenias’ had no cold damage at all, and it’s only now, months later, my G. jasminodes has a few spots where the leaves appear to have suffered from the cold. All these leaves are on the side that gets the most wind.
The Fix
Once it’s done, it’s done. You can’t really reverse cold damage, although it can be prevented. Covering your plants with frost-proof fabric or plastic in very cold weather will keep away or reduce frost damage. If you live in a colder climate, try to plant your gardenias in a spot where they will have some protection from cold winds.
Final Thoughts
Yellow gardenia leaves are trying to tell you something. When this shrub’s glossy green leaves start to take on a jaundiced appearance, it is a sign something is awry. We can determine by looking at the leaves whether the plant is getting enough or too much of something, as well as how healthy the roots may be. The good news is that most of these issues can be solved with a little investigation and mitigation.
