Gardenias are definitely beautiful and you likely love having them in your garden. They’re a joy to look at and they can also be fun to care for overall.
However, gardenias are also known for being a bit finicky in certain ways. If you don’t get certain things correct such as the pH balance of the soil, then you can encounter various issues.
You might have been caring for them for quite some time while having everything go fine. When you notice that your gardenia has leaves that are starting to turn yellow, it’s obvious that something is amiss.
Figuring out what exactly is wrong can be tricky when you don’t know where to start looking. There are a few potential causes that you’re going to want to know about.
Read on to learn why your gardenia’s leaves are turning yellow. One of the reasons listed below should be the cause of the issues with your plant.
1 – It Could Simply Be Normal
The first thing to consider is whether this yellowing of the leaves is actually normal or not. It’s possible that this is just a normal occurrence that you haven’t seen yet since you’re new to caring for gardenias.
Sometimes the older leaves on gardenias will start to turn yellow and drop off during the early days of spring. This is actually a natural thing because it’s making room for the new leaves that are going to appear soon.
As long as this doesn’t seem to be widespread, it’s not going to be something that you need to be concerned with. It’s something that you’ll see happen a bit in the early days of spring each year.
That doesn’t mean that you shouldn’t keep an eye on the plant, though. If you’re seeing many leaves start to turn yellow, then it’s more likely that something else is going on.
2 – Root Rot
When many leaves are starting to turn yellow at once, it’s possible that you might be dealing with root rot. Root rot is very dangerous and it has the potential to kill the gardenia shrub completely.
You can take the time to check to see if the plant is having issues with root rot. If your gardenia is in a pot, then you can tip it over and dig away a little bit of the soil to try to get a look at the roots.
Roots that are experiencing root rot will look significantly different from healthy roots. When the roots appear to be squishy and they’re looking brown or black it means that root rot has set in.
If this is the case, then there isn’t going to be a way to save your plant. When root rot has advanced this far it’s going to finish the job and kill your gardenias.
When the roots still appear to be white and they’re somewhat firm, it’s possible that you might have a chance to turn things around. You see, yellowing can also be caused by watering the plant too much or poor drainage.
Root rot is something that happens when a plant is getting way too much water. If your gardenia plant is showing signs of root rot, then that means that something is wrong and you need to try to correct it.
You might be watering the plant way more often than you’re supposed to. Gardenias are supposed to receive one inch of water each week, but watering a lot more than that will lead to substantial complications.
Sometimes you’ll be watering the plants correctly and will still have issues. This could be a sign that the soil isn’t draining properly.
You could have soil that is too dense and isn’t draining fast enough. This is causing you to water the plant when it’s still wet from the last time you watered it.
Try changing the soil and using a soil type that has excellent drainage. Remember to start checking the soil before you water the gardenias, too.
You’re supposed to avoid letting them dry out completely, but you never want the soil to be soggy. So long as you’re being careful you should be able to avoid issues such as root rot.
3 – It Could Be an Issue with Low Iron
Low iron is actually one of the most common reasons why gardenias will have leaves start to turn yellow. There’s a good chance that it might have low iron and that’s why you’re noticing yellow leaves.
Taking care of this problem isn’t as difficult as you might think it would be. It actually has to do with fixing the pH balance of the soil.
Earlier, it was mentioned that gardenias are kind of finicky, and they need to have the pH balance just right or they will start having issues. Yellow leaves can be considered one of the issues that pop up when the pH balance of the soil is not in the proper range.
Gardenias require the pH balance of the soil to be somewhere between 5.0 and 6.5. You should take the time to test the soil to see what the pH balance is currently.
If the balance is not in the right range, then that could very well be the reason why the leaves turned yellow. Adjusting the pH balance will involve using an acidic fertilizer that can help you to get things in the right range.
When you notice that the gardenia’s leaves are turning green again, you’ll know that what you’re doing is working. From this point forward, it’s going to be wise to use the fertilizer twice each month starting in the spring and ending in the late summer.
4 – Sunlight Issues
Sunlight issues could also cause gardenias to start having their leaves change colors. A gardenia plant is going to thrive when placed in full sun.
Some shade is going to be helpful to the plant when it’s really warm outside. If you live in a very hot area, then partial shade might wind up being the ideal option to choose.
Very hot weather and harsh sunlight could wind up scorching the leaves of the gardenia plant. This won’t turn the leaves yellow, but it will leave them looking burned and it might even cause buds to fall off.
If you’re in a warm area, then you want to plant them somewhere that will give them access to morning sun and afternoon shade. When growing gardenias in a cooler climate, they’ll be just fine tolerating full sun.
Those who are growing gardenias in containers should be giving the plants access to filtered sunlight. Direct sunlight will be too harsh when being grown in containers.
When you aren’t giving them enough sunlight, you’ll start to notice the plants will go through changes. Eventually, the leaves might start to turn yellow and they will begin dropping as well.
You can try to turn this around by fixing the situation as best you can. Give the plant more sunlight while being mindful of the potential problems that can pop up.
5 – Very Cool Weather
Even something as simple as very cool weather could cause a gardenia plant to have its leaves turn yellow. Generally, gardenias are going to do best when the daytime temperatures range between 65 and 75 degrees Fahrenheit.
Gardenias enjoy nighttime temperatures between 60 and 65 degrees Fahrenheit. When the weather starts to get way colder than that, it’s going to cause problems for them.
It’ll wind up bothering the plant enough that it will start to experience leaf yellowing. The leaves may also start to drop when the temperatures get too cold.
You might need to take steps to protect them if the weather is supposed to be too cold. Always try to keep an eye on the weather so that you won’t be caught off-guard by a situation like this.
Knowing the potential causes of yellowing leaves in gardenias should make you feel more at ease. Now that you have an understanding of what could be going wrong, it’ll be easier to troubleshoot the problem.
It might be that you’ll simply need to change the pH balance of the soil to fix things. That’s easy enough to do when you use the right fertilizer.
Sometimes a gardenia plant will have its leaves turn yellow naturally during the spring. This is just a sign that the plant is shedding old leaves to get ready for new ones.
It’s possible that more serious situations such as root rot could be the cause of leaf yellowing, too. If root rot is an issue, then it might wind up causing your plant to die.
You have to be careful about how you’re watering gardenias to avoid problems such as this. It’s also prudent to give them enough sunlight so that they can get what they need.
If cold weather is on the horizon, then you’ll need to protect the gardenias. Just keep all of this information in mind so that you can act accordingly to keep your plant in good shape.
Growing up with a mom who filled her home (inside and out) with all sorts of plants, Lisa got her start in gardening at a young age. Living now on her own with a home and yard full of plants (including an indoor greenhouse), she shares all the gardening tips she’s gained over the years.