I didn't know they had a 'lifetime' -- the one I use for cuttings is more than 40 years old. Have you considered taking cuttings for new bushes? They grow very fast.

Does the one in distress have good drainage and receive plenty of water? Funny, if the drainage is good, you can't water too much. If the drainage is poor, well....

Look for 'critters' on the back sides of the leaves, all the leaves. Maybe a little benign neglect if you don't see a reason for the trouble; mine seem to do best when white flies are controlled and everything else is not overdone.

Nell

Often the yellowing for gardenias means a lack of iron.

Betty

Lifetime, my ***. My cousin has had one in a pot on her patio for over twenty five years.

If the new growth is yellow with the veins staying green it woiuld indicate lack of iron.

Has something changed? For the plant to suddenly start dying after 5.5 years without anything changing would be strange. Have they been moved? fertilized? sprayed? Has something else changed?

Evergreen leaves usually last from a year to a year and a half so it is cause for concern to see them turn yellow quickly and fall. This is normal in the Fall for gardenias but not now. Try to rule out moisture problems and mineral deficiencies. After that check for additional symptoms. But check watering issues first.

For example, it should be very easy to tell if the plant has too little or too much water. Just stick your finger into the soil for two inches and see if it feels moist, wet or dry. It should be moist, never wet. If it feels wet then you may be watering too much; that can cause root rot. If it feels dry then it needs more water so water the soil around the plant with a water wand early in the mornings.

This time of the year you need to start increasing the amount of water. And if your plant has grown, if you have never increased the amount of water and if the soil feels dry too often, then now is a good time to increase your sprinkler's watering time. Water deeply and infrequently around the main trunk and thru the drip line.

Next, a soil test would be in order if you have not done one within the last 3-5 years. While you wait for the results of a "real" soil test, get one of those cheap Ph kits and use it to get an idea of what your soil Ph is. The idea is to detect whether your soil Ph is getting too alkaline for the gardenia. Take some quick action if you find that the soil Ph is very alkaline. A "real" soil test will be more accurate plus it will indicate whether the soil has any mineral deficiencies that can be addressed with Epsom Salts, Sul-Po-Mag or a fertilizer like Holly-tone (has a lot of extra minerals).

As buyorsell888 suggested, try to remember if you have sprayed any insecticides or fungicides on the gardenias or nearby plants. Some times the spray gets on the gardenia leaves and the plant does not like the chemicals. Some of the chemicals can also cause harm if applied at temperatures over 85F or so.

Scan the leaves (top and bottom) just to make sure the plant is not stressed by aphid infestations or attack by other insects.

Hope that helps you rattles2,
Luis