I grow my jasmine grand duke outside in socal where it is very hot and dry. I water it freely and keep it in bright shade. I believe that the yellowing is a watering issue, possibly too much. The blossoms only last a day or two as well, so that might be close to normal. Mine are white and fully open when they drop off, so too much water or even more importantly, not enough drainage, may be the issue there as well.

Hi gardenerme,
The flowers falling off sounds right, I did notice that after I water the plant, or when it rains, it does seem like the flower turns brown fast.
But I am stilll concerned about the yellowing, because I have all my plants in the fastest draining soiless mix you can imagine, Al's grity mix.
What's weird is that I have another one a smaller one and I planted that in plain old compost for kicks, and that one looks better and has alot of flowers. I am confused.

Have you checked for spider mites?

I noticed that my maid of orleans is turing a crappy yellow color too! Not sure if it's because I have her outside and it's been getting cold at night..that may be part of it. I just fertilized her with a dilute solution of liquid iron with copper. I better get her inside! I also stopped watering her too much but it doesn't seem to help...I think it's too cold out there, as the yellowing of the leaves stepped up extremely quickly from the last few nights. I'm hoping that is what it is...may repot her in some composted chicken manure next spring!

Yes..
I checked for spidermites my worse nightmare and found none. I have a couple of these plants and they are so prone to staying yellow. What's weird to is that their leaves hard hard. What kills me is that I have friends that live up in Canada that had a huge one, and that thing was so green. I asked what they feed it and she said only 20 20 20. Get this, that plant was planted in the crappiest of potting soil too. I don't get it.
What am I doing wrong? I even have it growing in Al's soiless mix and feeding it on a reg. basis with fertilizer.
I even had it in the full sun all summer.
The only green growth was the new growth, what I could get from it.I wonder if this plant has a high requirement for some sort of nutrient more than others?

Well, I killed my only GDoT years ago, but from what I've heard, it's just more finicky and harder to grow than other forms of jasminum sambac like Maid of Orleans. Here's my understanding:

1.It really likes it warm and humid -- above 60 degrees day and night, and high humidity. This is not one to leave outside until it's sweater weather.

2. It is more prone to chlorosis and leaf yellowing -- I suspect it doesn't grow as strong a root system as other jasmines, and so is more fussy about soil, drainage and watering. I think it might also benefit more from slightly acidic mix and/or occasional fertilizing with an acidic fertilizer. So it's not just the watering, or just the soil mix, but getting them all working together, which takes practice and attention to the details.

3. Even if you achieve perfect conditions, it will still grow tall and leggy, drop the lower leaves, and have old flowers turn brown and soggy before you'd like them to. That's just the price you pay for those double blooms, and that fragrance!

Jim

Not to mention they are probably more prone to mites than gardenias since if you can never get them in tip top shape, mites are are attracked to weak plants.... Man
But the fragrance is worth the challange!!

I have started adding a tablespoon of vinegar per gallon of water and it has greened up my whole garden. It seems that I have very base and alkaline soil, and my water is the same way. When I added vinegar, it changed everything.

Hum...Wonder if this would be good for potted plants that require acid soil such as citrus and gardenias to. I heard someone say that Miracid does nothing to change the PH of the soil....

Dig the soil around the plant by inch or two deep.Move the dug up soil as if you are mixing it around the plant,say, every two weeks.This will help draining the water from the soil below in other words water from the dug up soil will be lost by evaporation.It seems your plant needs some nitrogen fertiliser.Do not water unless the dug up soil gets dry.Grand dukes do well at temp. around 90+ deg. F. and plenty of light.It is awarm weather plant.Life of the flower is about 4 to 6 days.