Gardenia Problems in Desert Soils

Q. I have two gardenias in the backyard in 15 gallon ceramic pots with good drainage. One of them is doing pretty well and the other not so well. Our backyard is on the north side so both are shaded most of the day. The picture I sent to you has leaves turning yellow and then brown on the interior of the plant although the ends of the branches still have green leaves. Both plants are on drip and watered the same. I added iron on top of the soil and also Vigoro 10-8-8 plant food but it doesn't seem to be helping. The one I planted about 6 weeks ago has not done well. The other one was planted 3 months ago and is doing well with lots of flowers in May. Any suggestions for the one with the yellow leaves?



Gardenia leaves yellowing in potted gardenia. This could be salt accumulation.

A. It is tough to acidify soils here in our desert due to the alkalinity of our native soils and our water. So if you can acidify the soil as best as you can, it will help. Ways to acidify the soil include using composts, raw composts, manure products, sulfur, acids and aluminum sulfate.

My best shot at the gardenia is iron even though you added some. If you don’t use the right iron, it may not work. Use an iron chelate such as EDDHA with iron. You can pick up a one pound canister of this iron chelate locally at Plant World. I don’t know any other place it is being sold. Combine it with a soil application of your Vigoro fertilizer.

You might also consider some of the Miracid products.

Try to use fertilizers specially made for gardenias in the future if you can find one. If you can’t, use one for azaleas and rhododendrons. If you can’t find that, a third choice would be to use one for tomatoes, fruit trees or roses. Fertilize about once a month during the active growing season. These should be very light fertilizer applications.

Whenever you are watering a plant in a container, you want to add enough water so that about 20% of the water runs out the bottom. This helps keep salts leached from the soil. Our tap water coming from the Colorado River is quite salty and you need to make sure the soil stays flushed of salts coming from the water.

If you don’t, these salts will build up in the container soil and also cause exactly the problem you describe. You can’t let the soil go dry so it might be a good idea to buy one of those inexpensive soil moisture meters used for house plants which can give you a rough idea when the soil is dry and you should irrigate.

You want the soil to dry down between waterings but not too much. If it doesn’t dry down, you may develop root disease problems on camellias. If you let them get too dry, they will drop leaves and the remaining leaves will become scorched.

It is hard to judge when container soils are going dry. One way is to get an idea of its weight. You don’t have to lift it but just budging or moving it a little can give you an idea.