Quick Guide to Gardenia in Phoenix

Gardenia shrubs don’t grow as well in Phoenix AZ as they do in other parts of the country. They have a lot of elements working against them. Our soil is too alkaline, our summers are too intense, and even our water might be too salty for these fragrant shrubs.

When grown in the landscape, they are extremely vulnerable to chlorosis. In my experience, many of the gardenia shrubs in Phoenix suffer from this issue. This symptom shows up as pale leaves with dark vein outlines. The gardenia won’t grow as well or flower like normal. It may die suddenly from stress.

Is it possible, then, to keep Gardenia jasminoides healthy and happy in a desert garden? Yes, with some careful planning and yearly upkeep.

Proper Placement in the Landscape

First of all, remember that gardenia shrubs need shade in the low desert. An east facing exposure is fine. They can’t handle the afternoon sun in the summer, so even if you set everything up correctly you’ll still probably lose the plant if it’s getting too many hours of sun. Courtyards are a great place for a gardenia, especially near a fountain.

Soil and Care

Planting gardenias in containers works best for the low desert. Potting soil is much better for them than the clay soil we have in the ground. Gardenia plants prefer acidic soil with plenty of compost, so a nice rich bag of potting soil will give the best results.

When I plant a container for something like gardenia, I’ll usually fill the bottom half of the pot with a basic “Gro Well” or similar potting soil, and the top half can be filled with a specialty potting soil with extra fertilizer ingredients like “Foxfarm Ocean Forest”. I do this because the plants like having the extra nutrients but there’s no point in filling the entire container with an expensive soil because the roots aren’t able to reach it yet and it will just wash out.

Make sure the roots have a good amount of space to grow into. Pots should be at least 2ft in diameter to avoid the pot drying out too often or constricting the roots.

Add a thick layer of mulch to the surface of the pot for best results. I also like to add a bit of Osmocote slow release fertilizer for the micronutrients and added nitrogen.

Maintenance of Gardenia

Water gardenia every day or every other day during the summer (in most cases). The soil shouldn’t be allowed to dry out to the extent that desert plants can dry out. Periodically spray the leaves down as a treat. If there is a drip irrigation system delivering water, it’s still helpful to water by hand once or twice a month because sometimes the emitters don’t cover all of the soil around the plant.

Add mulch or composted mulch around the gardenia regularly. This should be done at least twice a year for best results. Other fertilizers like worm castings or liquid flower food are appreciated by gardenia shrubs but mulch is something that is absolutely necessary. Mulching keeps the moisture in the soil. Planted in the ground, mulch will help keep chlorosis away.

If chlorosis is already present, sulfur from a garden center can help adjust the pH around the roots of the gardenia. Sprinkle it around the plant and water it in, then wait a couple of weeks to see results.