How to treat Gardenia with leaves turning black?

[3jidaddy]

Hi. My first time growing gardenias and I found issues.

1. I see that some flower buds were cut off before blooming. 

2. Some leaves are turning black.

3. Some with insects even though I have been applying eco oil weekly.

Appreciate me if you could give me some advices. Thank you. 

 

 

 

 

[JacobZ]

Hi @3jidaddy,

Growing gardenias for the first time can be challenging, but addressing these issues is manageable with some care.

The flower buds likely dropped prematurely due to environmental stress like inconsistent watering, temperature changes, or insufficient nutrients. Ensure the soil is moist but not waterlogged, maintain consistent watering, and use a fertilizer such as Scotts Osmocote Roses, Gardenias, Azaleas And Camellias Controlled Release Fertiliser to support bud development.

The black leaves may result from fungal diseases like sooty mould or overwatering. Check for pests like aphids that secrete honeydew, as this can lead to mould. Remove affected leaves, improve air circulation around the plant, and water only the soil to avoid wetting leaves.

If insects persist despite using eco-oil, ensure you're applying it correctly, covering both the tops and undersides of leaves and physically remove any eggs or insects like those I have circled below. 

Keep the plant healthy overall, as strong gardenias are more resistant to pests and diseases.

Allow me to tag @mich1972 and @Noelle for their thoughts.

Thank you for your questions and if you have any more, please don't hesitate to ask.

Jacob

[Noelle]

Hi @3jidaddy 

Jacob's given you some very practical and timely advice! Flower buds dropping is usually a good indicator that the plant/s are not happy, and it's usually due to weather or watering conditions. Don't over water gardenias.

[3jidaddy]

Hi, @JacobZ 

Thank you for the detailed info. Much appreciated!

I have been using the fertilisers you mentioned. Also I have been giving the flower food when I water them once a week. 

I live in south Brisbane and it has rained a lot these days. I think it may caused overwatering. Can you advise me what can be done as weather is something that is out of my control.

The plant pot is located at the front yard where there are lots of air circulations and morning sun so I am thinking this may be related to the weather?

For the eco oil, I have been applying from the top I guess. I will apply the undersides. 

Thank you again.

[3jidaddy]

Hi, @Noelle 

Thank you for your advice. As I mentioned to the JacobZ's reply, I think it may be due to the weather. Do you have any tips for the  rainy days? I live in South Brisbane. Thank you. 

[JacobZ]

Hi @3jidaddy,

Do the planters your gardenias are planted in have a drainage hole at the base?

If there is nowhere for excess water to go, it will sit in the soil, causing stress for your plants.

If there is no drainage plug in the planters, it would be worthwhile to drill a hole in the base of the planter to allow excess water to escape.

Let me know what you think.

Jacob

[3jidaddy]

Hi, @JacobZ 

Yes. The plants are from Bunnings and have a drainage. I also put some styloform at the bottom so that it is drained.

[Noelle]

Hi again @3jidaddy 

Really important to make sure that the soil drains well, and quickly when you have torrential tropical storms! Gardenias enjoy a moist but not wet soil so check the drainage to ensure excess water can get away from the roots reasonably quickly. If the plants are in a planter box, which it looks like they may be from your photos, then make sure there are sufficient holes in the base and use a suitable free draining potting mix specially formulated for acid-loving plants like these.

[JacobZ]

Hi @3jidaddy,

You could also move the planter undercover so it is not exposed to the rain. This way you can closely control the watering to ensure it is not being overwatered.

Let me know what you think.

Jacob