Proper Care For Gardenias In Phoenix - Knowledgebase Question

Phoenix, AZ
Question by mroscoe
March 2, 2000
My gardenia plant has white residue on the top of the leaves and I found small brown aphids on the underside of the leaves. Is this considered to be called scale? Will an insecticidal soap help to resolve this problem? What steps need to be taken in the desert to grow and have gardenias bloom?


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Answer from NGA
March 2, 2000

0

of water from the hose should work. Spray underneath leaves, in between, etc. Do this daily.

If that doesn't work, try a soapy water spray. Use 1 teaspoon to 2 tablespoons of liquid detergent soap per gallon of water. Use regular, not concentrated soap. Don't use soaps with lemon, as the citric acid can burn plants. Start with the lower amount and work up as needed. Spray as often as needed. As with any spray you might wish to test it on a few leaves first before you treat all your plants. Next on my list would be an insecticidal soap spray.

Ladybugs and their larvae are voracious eaters of aphids. They often "arrive" a week or two after the aphids, so not spraying with chemicals is a good idea if you'd like to attract them to your garden to consume aphids for you.

As for growing gardenias, they are a marginal plant here in the low desert. They prefer a cooler, moister environment with acidic soil. Our soil is highly alkaline. You can try amending the planting soil with peat moss or pine needles, using a product such as Miracid, and planting where they will receive protection from hot afternoon sun. Because they are marginal, it is likely they will be stressed without continual care. Research shows that insects and disease seek out stressed plants for attack, which seems accurate in your case as the gardenias have both aphids and probably powdery mildew. You might be better off replacing them with more appropriate desert-adapted plants. Good luck! of water from the hose should work. Spray underneath leaves, in between, etc. Do this daily.

If that doesn't work, try a soapy water spray. Use 1 teaspoon to 2 tablespoons of liquid detergent soap per gallon of water. Use regular, not concentrated soap. Don't use soaps with lemon, as the citric acid can burn plants. Start with the lower amount and work up as needed. Spray as often as needed. As with any spray you might wish to test it on a few leaves first before you treat all your plants. Next on my list would be an insecticidal soap spray.

Ladybugs and their larvae are voracious eaters of aphids. They often "arrive" a week or two after the aphids, so not spraying with chemicals is a good idea if you'd like to attract them to your garden to consume aphids for you.

As for growing gardenias, they are a marginal plant here in the low desert. They prefer a cooler, moister environment with acidic soil. Our soil is highly alkaline. You can try amending the planting soil with peat moss or pine needles, using a product such as Miracid, and planting where they will receive protection from hot afternoon sun. Because they are marginal, it is likely they will be stressed without continual care. Research shows that insects and disease seek out stressed plants for attack, which seems accurate in your case as the gardenias have both aphids and probably powdery mildew. You might be better off replacing them with more appropriate desert-adapted plants. Good luck!

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