Gardenias have a bit of a reputation for being tricky to grow, but they’re not. You simply have to know what the plants need to stay happy, and give it to them.
Here’s how to grow these beautiful, classic plants.
Where to Grow Gardenias
Probably the most important part of success with gardenias is where you plant them. They like:
- Morning sun or sun from an east-facing or north-facing exposure.
- Acidic soil (soil pH of 6.0 or lower).
- Well-drained soils that are high in organic matter (not super heavy sticky clay or sandy soils).
- Room to grow. While you can prune gardenias, they’re happiest when allowed to assume their natural shape.
Read the plant tags to see how large the variety you’re growing is projected to get and choose a spot that can accommodate their size.
How to Plant Gardenias
- Test the soil: Let’s say you have everything gardenias need right in your garden, but you’re not sure about the soil pH. Before you plant, definitely get a soil test (your local cooperative extension agency can do that for you) or buy a soil test kit from the garden center and follow instructions to test the pH yourself. This is critical to success with gardenias. If the pH is good (6.0 or lower), you can move to step 2. If it’s too high, lower the pH by applying Aluminum Sulfate or soil acidifier for gardenias, camellias, azaleas, and hollies, according to pack instructions. Once that’s done, you can dig.
- Dig the hole: Always dig just as deep and twice as wide as the plant’s rootball.
- Plant the Gardenia: Place the gardenia in the hole and fill in around the plant with the same soil you removed. The top of the gardenia rootball should be level with or slightly higher than the surrounding soil. If it is lower, remove the plant from the hole, fill in a bit with soil, and replace the plant.
- Water: Give the newly-planted gardenia a good soak. Turn the hose on all the way and count to 30 or water with three gallons of water.
- Mulch: Keep the soil moisture consistent and the garden tidy by mulching. Spread mulch in a layer of 2-3 inches (no deeper) around the plant. Keep the mulch away from the plant stems.
*Tip: If you live where the soil is highly alkaline, it is worth growing gardenias in containers so you can control the soil pH.
How to Water Gardenias
Water gardenias every day just after planting, gradually increasing the time between watering. You never want the soil right around the plant roots to totally dry all the way out right after planting. During the first growing season keep tabs on the plant. Until it has grown roots into the surrounding soil, you’ll still have
to water once or twice a week. The second growing season and beyond water gardenias only if your area hasn’t had a good soaking rain for 3-4 weeks.
How to Fertilize Gardenias
Fertilize gardenias in spring right after the last frost with a balanced fertilizer labeled for acid-loving plants. (Look for azalea, holly, or camellia fertilizer.) Fertilize again 6 weeks later, which should be close to bloom time. Avoid fertilizing in the fall, as this can cause new, tender growth to sprout, which will then be damaged by fall frosts.
How & When to Prune Gardenias
Start by buying the right gardenia for the space where you’re planting it and you’ll be ahead of the pruning game. However, if you need to prune, here’s when and how to do it.
To reduce size or to shape
Prune immediately after flowering. Always cut back to a leaf and don’t leave an empty twig hanging out. gardenias form flower buds for the next summer after blooming, so if you prune in spring before they bloom, you’ll cut off all of the flowers.
To remove winter-damaged growth
Think your gardenia got zapped by a frost? Wait until new leaves start sprouting to remove dead growth. You might be surprised at what’s still alive!
Give gardenias what they want, in terms of sunlight, soil, and water, and they won’t cause you a lot of problems. There are a few common issues, though. Here’s how to identify them and what to do.
- Yellow leaves: Leaves may be yellow because they aren’t getting the right nutrients, usually because the soil pH is too high. This usually shows up as yellow leaves with bright green veins. Test the soil and fix the pH before fertilizing. Leaves also turn yellow when plants are overwatered, but the whole leaf will turn yellow and fall off. If the soil pH is correct, cut back on watering.
- Leaves are falling off, starting with oldest leaves: The plant might have root rot. There’s not much you can do about this. Start over in a new place and make sure the soil drains well.
- Leaves have a greyish “powder” on them: This is powdery mildew. Increase air circulation around the plants and take care not to water their leaves. Use preventative fungicides the next year.
- Leaves have a black coating on them: This is sooty mold and it is related to an insect problem. Identify and treat the insect problem, and the sooty mold will go away.
- Shrub won’t bloom: It is likely that you pruned early in the season and cut off the flowers. Delay pruning until after flowering.