Garden Detective

Garden Detective: Gardenia’s problem linked to water

Gardenias need to be planted in well-drained soil.
Gardenias need to be planted in well-drained soil. Big Stock Photo

Q: I’m hoping you can help me with my Monrovia gardenia topiary. It’s planted in a large pot located at my front door. It receives morning sunlight from sunrise until early lunchtime. It’s on drip for 4 minutes every day. I’ve talked to the experts at a local nursery and they told me to keep it moist, but don’t overwater, and to feed it monthly, which I do per box instructions. The issue is that the leaves turn yellow and brown and fall off and I haven’t had a successful bloom. The buds where the blooms should be turn brown, dry, and fall off with the yellow leaves. Can you help me so I receive gardenia blooms?

Caroline Johnson, Folsom

A: To successfully grow gardenias, they need to be planted in well-drained, moist but not wet, acidic soil, according to UC master gardener June Bleile. Yellowing, falling leaves are often due to underwatering or overwatering.

Your 4 minutes of drip irrigation might be adequate or not enough, depending on the size of the emitters. Test by pushing your finger down into the soil to about 2 inches. The soil should feel moist.

Testing moisture this way may be difficult with a gardenia because it has a fragile root system near the surface. Using a moisture meter might be more satisfactory.

If your topiary is in a clay pot, remember that the clay pot can get hot in the sun and dry out faster. Shading the container and mulching the planting with 2 inches of organic material will aid in keeping the soil moist.

If the pot is in a saucer, be certain that the pot does not stand in water. This could lead to root rot and would be a breeding place for mosquitoes.

Fertilize your gardenia during the growing season, between April and November, with a fertilizer for acid-loving plants, following the directions on the container.

By definition, topiary are clipped often to keep their shape. But pruning can interfere with gardenia bloom.

The best time to prune a gardenia plant is after it has finished blooming. Pruning too early will remove flower buds. Pruning too late destroys next year’s blossoms since it removes the newly formed buds. Prune to cut out any dead branches, to shape and to control size, cutting back to just above a leaf node, 4 to 6 inches from the tip.

Garden questions?

Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties. Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to h&g@sacbee.com. Please put “Garden Detective” in the subject field and include your postal address. To contact UC Extension directly, call:

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