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Rhododendrons and Relatives: Why are these leaves browning?

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Forum: Rhododendrons and RelativesReplies: 9, Views: 126
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killdawabbit
Christiana, TN
(Zone 6b)

August 13, 2010
11:26 AM

Post #8037736

This is an Autumn Sunset that I bought this spring. It grew beautifully all spring and most of the summer and now some of its leaves are browning. Anyone have any ideas why?
I used Osmocote in the potting mix and haven't given it any extra fertilizer. It gets about a half-day of sun, afternoon. My azaleas in the ground get lots of sun and do well.
My other ericaceous plants do very well in the same potting mix.
Thanks, Kyle

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ecrane3
Dublin, CA
(Zone 9a)

August 13, 2010
3:00 PM

Post #8038106

Could it be too much sun? It may not be as sun tolerant as your others (assuming they're different cultivars?). Or because it's in a pot its roots may get hotter and/or its moisture level doesn't stay as consistent as the ones that are in the ground which would cause it to be less happy. Afternoon sun tends to be hotter and more stressful than morning sun, so if there's a spot you could move it where it would get a half day of sun in the AM instead of the PM you could see if it seems happier.
killdawabbit
Christiana, TN
(Zone 6b)

August 13, 2010
3:47 PM

Post #8038172

Thanks. It's in a clay-colored pot and gets watered every day. But I have moved it to a little less sun for now.
I wonder if I over or underwater. I lost a R. fortunei. It was beautiful and it just started wilting--VERY slowly. It was in a pot in the shade. I know the mix it's growing in has to be OK because when I received it it was yellow and after I potted it it greened up perfectly. Now it's dead. :-(
luis_pr
Hurst, TX
(Zone 7b)

August 13, 2010
4:40 PM

Post #8038251

Drought causes all leaves to wilt and new leaves to burn, and eventually all leaves begin to turn brown in a random pattern thru the shrub. Since the root system is not fully developed, drought stress m-a-y be causing the leaves to brown out.

Fertilizer burn, which normally occurs at the ends and edges of leaves, could be another possibility. In this case, you can water the soil to try and wash out excess fertilizer.

Azaleas roots are usually in the top 4" of the soil so insert a finger into the soil to determine if you need to water. If it feels almost dry or dry then water. Repeat this daily for 1-2 weeks so you notice a watering pattern (that is, you notice that you water every 2/3/4/etc days). Water with the finger method if the temperatures go up or down by 10-15 degrees and stay there. This and mulch should help control over and underwatering.
killdawabbit
Christiana, TN
(Zone 6b)

August 13, 2010
6:19 PM

Post #8038419

Thanks, Luis. I wouldn't be surprised if I have overwatered them both.
arfitz
Caldwell, NJ
(Zone 6a)

November 18, 2010
1:17 PM

Post #8218965

Usually when the tips of the leaves brown it is because they are sunburned or havent gotten enough water.for a longtime
I'm not sure about your area, but here in NJ we have had record heat for most of the mid and late Summer. By the way sometimes the burned foliage takes several months to show up, not necessarily the days immediatly after the burning exposure.







i'm not sure about your area but nera
killdawabbit
Christiana, TN
(Zone 6b)

November 18, 2010
9:53 PM

Post #8219727

I believe I overwatered it. It died.Since then I have stopped watering rhodies as frequently.
luis_pr
Hurst, TX
(Zone 7b)

November 19, 2010
12:20 AM

Post #8219754

Sorry to hear that. Overwatering can make the roots develop root rot when the roots are exposed to very high moisture levels for too long. The symptoms of root rot are identical to those of not enough water because in both cases, the roots are unable to send enough water to the part of the pant that grows above ground. The only way to confirm it is by pulling the plant out of the pot and insecting the roots. If they look bad or smell rotten then you can assume the plant has root rot.

Two suggestions: (1) The finger method that I mentioned above should help you determine when to water and when not to. (2) Confirm that the drainage hole was not stopped up and consider planting another azalea but this time, add about 1/2 an inch to one inch of pebbles or snall rocks to the bottom of pebbles to improve drainage even further. Maybe these two ideas together will improve your chances. Choose a planting location where it gets shade in the afternoon during the summer time and which is not too windy.

Good luck!

Centaurea

Centaurea
Amsterdam
Netherlands
(Zone 8b)

November 20, 2010
7:55 AM

Post #8221711

I highly encourage looking on google for "Container Soils - Water Movement & Retention VIII" Tapla's info on container mixes is absolutely the best thing you could ever learn about container gardening, even if you only do it a little, no exaggeration. It saved my plants and I haven't lost a single one (including cuttings) to root rot since I had that "aha" moment reading that info, and made a gritty container mix for my plants. I'm not affiliated with him at all, I'm just that happy. You can combo the gritty mix and semi-hydro (pot with drainage inside pot without, keeping water level near a mark at or below the interior pot, many plant send "water roots" down into water (but also need the mix so the majority of roots can breathe) so you don't have to water every day, and no root rot). As a stop-gap if you don't want to invest in buying supplies just yet, you can put a wick in the pot. It should be a cotton rope or shoelace or some other type of long floppy object that will wick water. It should drape out of a drainage hole and go up at least 1/2 way into the soil in the pot. It will help wick away the water that is causing the root rot. It will rot itself though after a few months in warm weather.
killdawabbit
Christiana, TN
(Zone 6b)

November 20, 2010
4:53 PM

Post #8222403

Thanks, everyone.

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