Osmanthus fragrans - why is some new growth turning brown?

JuttahAugust 20, 2011

I'm stumped! A few (but not all!) of the newly-emerging leaves on my sweet olive (Osmanthus fragrans) are turning brown and shriveling. Click here to see what it looks like (opens in new window).

This only started a few days ago. Otherwise, the plant looks healthy, other than a few scorched old leaves from back in June when we hit 112. I looked real close but didn't see any bugs. What could it be?

(Tried googling -- but all I can find are similar problems in marijuana plants! LOL! And the few O.fragrans "brown leaf" posts I've found on this site all involve older leaves, not new growth.)

Current growing conditions:

- Direct sun 10am to 3pm - otherwise shaded by house and wall

- Daytime highs currently averaging mid-90's to low 100's, with 40-60% humidity (monsoon season; normally it would be hotter and drier)

- Watering 2x week for about 20 minutes if no rain. Rained like crazy 2 days ago!

- Mulched with 3 inches of mesquite leaves and detritus

- NO fertilizer - but I did put down 1/2 cup of cottonseed meal earlier this year

- Planted last October

- Applied Dominion systemic (Imadacloprid) last March to control thrips

Anybody experienced something similar? The link below has more pictures.

Here is a link that might be useful: More Osmanthus pics

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What is the ph of the soil?
It looks orange, test the soil to make sure it isn't too alkaline.
Tea olive like it on the slightly acidic side.
Buy pine mulch for it also, at least 2-3 inches to hold moisture in for it. It likes pine mulch.

    Bookmark   August 20, 2011 at 11:31PM
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yellowthumb(5a Ontario)

I could be just wind and sun damage. In general you tree looks fine to me.

    Bookmark   August 21, 2011 at 12:23AM
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rhizo_1 (North AL) zone 7

That location will provide a great deal of reflected heat and light, something that the osmanthus may find difficult to tolerate in your climate. Osmanthus prefers a fair amount of protection from the full sun, especially during the hottest part of the day...which just happens to be when your plant is getting irradiated and baked! ;-)

I agree that you should know, with some accuracy, the pH of your soil. As a matter of fact, a soil test might not be a bad idea. You may find out that fertilization is required for all your plants....or not. Home pH meters can be incredibly bad, as can moisture meters. As can home soil testing kits! I always recommend springing for a soil test.

I disagree that you plant looks fine. The leaves should be uniformly dark green, and the shrub should be full.

Does your twenty minute watering session do the job? Have you dug around in the soil (not right at the root system, please) about 30 minutes afterwards to see how moist the soil is?

In the southeast, where this plant flourishes in some locations, you'll find the healthiest plants under the high shade of tall pines (for example), or in locations that receive full sun in the morning but some shade all afternoon. My Osmanthus, planted in hard, red Alabama clay with no irrigation, is in the sunlight until about 11 ish, when the shadow from the house begins to protect it.

NOW! About your use of the imidicloprid. You might not know that this systemic pesticide translocates throughout the vascular system and can be found, subsequently, in the POLLEN and NECTAR of the flowers. Every single insect that visits your osmanthus will be exposed. I even have hummingbirds all over mine! Imidicloprid is banned in some countries because of this. Bees carry the tainted goods back to the hive where it is distributed to all inhabitants. This is not a good thing.

There are also some worrisome studies out that appear to point the finger at this chemical for INCREASING thrip populations, rather than decreasing it. It is well documented that spider mite numbers soar with the use of Imidicloprid. Maybe something to think about?

Here is a link that might be useful: Soil testing labs

    Bookmark   August 21, 2011 at 8:55AM
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Imidicloprid is like cotton candy to spider mites. Not only that, but you are killing off your beneficial insects along with bad. Guess what bugs will come back with a VENGEANCE once the good ones are gone? You guessed it, the bad ones......That is just 'nature' working side by side with pollution and man's destructive behaviors. It his own demise.

Ever see what happens once the grass in your lawn is killed off with the weeds? You guessed it, the weeds come back.

To me that looks like either thrip damage that is rotting off, or sun burn. I can tell you that mine hates full sun and in fact it was Rhizo who suggested to keep mine in more shade. Worked like a charm:-)

Good luck


    Bookmark   August 21, 2011 at 9:06AM
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Thank you for the helpful replies!

Something I failed to mention - we used to have a gorgeous 12' tall Willow Acacia just to the left (south) of the Osmanthus, which would've provided much-needed midday shade. Unfortunately two freak cold snaps (14 and 16 degrees) back in February killed just about every Willow Acacia in Tucson. I replaced it with an 8' Netleaf Hackberry, which is thriving, but it'll be a few more years before it gets big enough to shade my poor Osmanthus. I'm going to look for some shade cloth today.

The soil pH is just a hair over 7 according to my el-cheapo soil probe :) You're right though, my plant looks like it's heading towards chlorosis. Very common issue here in the desert.

About the imidicloprid - I hate applying stuff I can't even pronounce, but I was desperate. Last winter, every new leaf on this plant was stunted, puckered, and wrinkled by thrips. So a neighbor gave me a nearly-empty bottle of Dominion to try, and it seems to have done the trick.

Before that I tried tin foil and daily jets of water to no avail. Fortunately I've never seen any insects visiting the Osmanthus flowers, at least not during the daytime. In contrast, our late Willow Acacia was covered in bees and other pollinators whenever it bloomed. (Also - just about every wild honeybee in Tucson is Africanized, so we don't worry too much if we kill a few here and there, hehe.)

What can I try for the thrips - insecticidal soap? I got rid of spider mites on a nearby juniper with rubbing alcohol, would that work? Would better cultural practices help? I'm open to any non-toxic suggestions... thanks again all you helpful people!

    Bookmark   August 21, 2011 at 10:38AM
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yellowthumb(5a Ontario)

The tree looks a bit sparse, but sometimes Osmanthus does that, send out long shoots with few leaves. The stem looks thick to me. You can tell the tree just had a flush of new growth, the new leaves normally start from red-purple, then pale green, then deep dark green.

I put all my container grown Osmanthus in full sun (I am in Zone 5 though), I have two. What I discovered is that more sun, more compact, more flowers. But you do have to watch the watering. You never let them wilt, otherwise, brown tips will follow. They do love slight acid soil, this is a must.

Is Imidicloprid a major ingredient of Bayer Advanced Protect and Feed? I have mixed feelings of this systemic. I know I should go organic, there are so many organic ways. Neem oil is my favorite. But sometimes, you just can't get rid of some pests like Mealy bugs. They could be hiding in the roots, and what I am treating is a precious plant. So I will treat it once with guilt. You know what, mealy is gone. Then I treat them regularly with Neem. Works perfect. Summer sun and wind will rid most of them all by nature.

    Bookmark   August 21, 2011 at 3:20PM
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mehitabel(z6 MO)

My experience is like yellowthumb-- I grow mine in full sun, but the leaves brown off seriously if it gets too dry.

The climate here is a lot more humid than Tucson, but I actually water my osmanthus more than twice a week. In my experience they like to be moist. Not wet, of course, but drying off between waterings leads to the brown leaf syndrome.

My guess is new leaves being creamed by too much dryness.

    Bookmark   August 21, 2011 at 6:45PM
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