Question
Will, I just did a pH test for my jasmine plant. It came back at 7.5. This is a 3 ft jasmine in a 14 in container. I sprinkle it with Holly Tone and use miracle grow every other week. I have had it for 3 yrs. Last year, just before bringing it inside, the leaves began getting small individual brown spots. Eventually those leaves would drop off. Leaves are now sparse on the plant. I have treated it twice with liquid copper. The plant still doesn't look good and it is still producing leaves with spots, perhaps at a slower rate.
I just purchased a gardenia tree that I have in a  18"x30" container. The leaves on the underside of the plant are turning yellow and dropping at a fast rate. The veins of the leaves are remaining green so I was thinking it might be an iron deficiency. I cannot seem to find iron to add to the plant.

Any help or suggestions with these 2 plants would be most appreciated!

Answer
Hi Cheryl,

I think you are too focused on chemicals while overlooking some more basic issues.

The soil pH for your Jasmine should be no higher than 6.8. Yours is unusually high and suggests that the soil or water quality that you are using is not good. When pH is too high or low, nutrients do not dissolve properly for the roots to absorb. So improper pH will cause plants to exhibit nutrient deficiency even though those nutrients are available in abundance in the soil. Applying liquid copper is a  mistake because you don't know that it is lacking and because it is a micro-nutrient used in minute quantities and is too concentrated when applied alone.

Holly-Tone is not intended for indoor use and is used on acid-loving plants, such as Gardenias, but not Jasmine. Miracle-Gro should only be used on healthy, vigourously growing plants and never more than at half strength monthly. The excess nutrients in the soil may be causing leaf spotting.

More importantly, your Jasmine is over-potted and that is probably causing root rot and the decline of your plant regardless of pH and nutrient availability. I suggest you carefully unpot your Jasmine and remove all of the excess soil not in direct contact with the roots or original rootball. If you do not find a lot of healthy roots, then you may as well discard the plant. Otherwise, move it into the smallest pot that you can fit the roots into snugly. Then flush lots of clear water through the repotted plant to remove excess nutrients and re-set the pH. If your local tap water is on the hard side, then you will have to use distilled or filtered water. Thereafter, water only when the top couple of inches of soil is dry.

Stop fertilizing your Jasmine altogether until it has fully recovered. Keep it indoors in a sunny window. Protect it from temps much below 60 degrees F.

I don't have enough information about your Gardenia (size, light, watering routine, etc.) to provide much help. Gardenias do require acidic soil and I am sure that is what it was planted in unless you repotted it and used some other soil. The soil pH should be in the 4.5 - 5.5 range. If it is higher than that, then use iron sulphate to raise the pH. If you cannot find it, then use Mir-Acid plant food at half strength. That said, it is unlikely that a pH problem would cause the symptoms you described so soon after purchase. It is more likely to be a problem with light, water or pot size.

I have written articles on Jasmine, Gardenias, repotting and fertilizing that I will email for free to you (or anyone else) who emails a request to me at [email protected].

Please let me know if any of this is unclear or if you have any additional questions.

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

Visit my website at: A link to HorticulturalHelp.com