Over Watered Azaleas? - Knowledgebase Question

Lincoln, CA
Avatar for lbrigleb0
Question by lbrigleb0
August 2, 2005
I live in Lincoln, CA ? Sunset Zone 9. Early this spring I planted several of your Red Ruffles Azaleas. Five of them are in a 4? wide planter bed on the North side of the house. The bed is filled with a 15-18? layer of planters mix composed of 20% clay topsoil, 60% black humus and 20% sand. All five azaleas currently get 2-2 ? hours of direct sun in the morning. Two of them get another 1-1 ? hours in the late afternoon. A third gets about an hour, and the remaining two get filtered or no sun in the afternoon.

The two plants getting the most sun appear to be healthy. The other three (especially those with no afternoon sun) appear to be failing. The most noticeable sign is that the leaves on new growth are discolored. Unlike the dark green older leaves, the newer leaves have dark green borders and veins, but are a bright yellowish green everywhere else. I have taken clippings from these plants to the nursery where I bought them. Their diagnosis is too much water, and they recommended restricting irrigation to an every other day schedule.

My planting bed is being irrigated by a grid of Netafim dripper line with 0.6 gph in-line emitters on 18? centers, and has about a 2? layer of cedar bark mulch. In recent weeks (with record high temperatures), I have been running this circuit 15 minutes/day 5 days/week. Although the portion that gets afternoon sun is somewhat dryer than the rest, this seems to keep the entire bed in a state that I think would be described as ?moist, but not soggy?. The surface is damp, fairly cool and readily crumbles into fine particles when crushed. Deeper down is pretty much the same. Today, I dug a 3? diameter 9? deep hole next to the root ball of the worst looking plant. The soil seemed to be uniformly damp (but not soggy) throughout that depth. I then filled the hole with water and let it drain. It was completely drained after 15 minutes.

With that as background, here are my questions relating to the azaleas:

1) Does the situation described above sound like too much water?
2) If so, what can be done to get them back on track?
3) If not, what other suggestions do you have for improving the health of these plants?

On a more general note, can you also please clarify what is meant by ?constantly moist, but not soggy?. This phrase is used in several responses to your FAQs on azaleas (and other plants), saying that azaleas prefer (or require) that condition. However, in your on-line plant catalog, the growth conditions page for Red Ruffles Azaleas says ?Water regularly, when top 3 in. of soil is dry?. To me, these don?t sound like the same thing. What am I missing?

Many thanks for your help.

Answer from NGA
August 2, 2005
Azaleas prefer a slightly acidic soil (yours may be too alkaline so you might want to have it tested). The pale leaves indicate a nutrient deficiency, probably because the soil is not acidic enough and the roots cannot take up the nutrients. Try feeding with a specialized azalea food (in amounts as listed on the label).

While overwatering can leach nutrients out of the soil and cause root rot, off-colored foliage almost always indicates an imbalance in soil pH. (If soil is too acidic (or in this case, too alkaline), nutrients can be bound up and not available to plant roots.)

To help clarify soil moisture recommendations, consistently moist means there is little fluctuation between moist and dry soil. It's a little like feast or famine - plant roots appreciate a steady moisture content in the soil rather than a flood and then a drought. The catalog description is saying much the same thing - soil remains moist 3" beneath the soil surface for quite a long time after watering. You can test this by watering your azaleas as usual and waiting 3-4 days, then digging a hole near the roots of your plants to check the soil moisture content. If the soil is moist 3" below the soil surface, you won't need to water again for a few days; if it is dry 3" beneath the surface, it's time to water; if it's soggy wet, the drainage is not very good and your plants could develop root rot.

Hope this answers all your questions!

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