Problems with Indoor Avocado: Yellowing Leaves and Browning Tips

iluvbotany4life(Zone 5)December 28, 2010

I grew 2 avocado plants from the pit, and they've been growing well for quite some time. They are now about 2 ft tall. A few weeks ago, I noticed some slight yellowing on the leaves and browning at the leaf tips. I checked the roots and noticed that they were pretty root bound and needed repotting, so I repotted them. But the yellowing and browning has gotten worse. Here is a picture of how it looks now. http://www.flickr.com/photos/17398687@N02/5301425262/

As you can see in the bottom right picture, I have the plants under fluorescent light in the daytime. Also I've noticed that new leaf growth is turning white, drying, and falls off to the touch (Upper left picture). I thought maybe the yellowing could be N deficiency, so I fertilized with a houseplant fertilizer and this hasn't seemed to help, so I'm thinking maybe chlorosis? How can I treat chlorosis in a potted houseplant? I don't really want to fertilize again with it being wintertime. And I still don't know why the leaf tips are browning? I have also noticed that the lower leaves (which are very large) are very stiff and drooping. Is this from inadequate light? Because the fluorescent lights don't really reach the lower leaves well. Do you think the fluorescent lights are too intense on the upper leaves? Desperately need advice on this ??

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greenman28 NorCal 7b/8a

Hey, Botany!

Avocados often do poorly during the Winter, but that's no reason to abandon them.
I've had pretty good success with mine, and I'll link to the Thread I started on this subject.

I provide my plant with a well-draining soil that can be watered thoroughly, and a sunny window.
Can you re-locate your plant near a window?

Yellow leaves often result from over-watering - or a soil that holds excess moisture.
In *most* plants, browned leaf-tips indicate dead roots/root-tips (As Above, So Below).
However, with Avocados, I think browned leaf-tips are par for the course (indoors),
in light of the low humidity and lack of adequate air circulation in most homes.

Before I can advise you further, I need to know what kind of soil you're using,
what kind of container and drainage is provided, and what sort of fertilizer you used.

Josh

Here is a link that might be useful: Avocado converted to Houseplant (pics)

    Bookmark   December 28, 2010 at 5:26PM
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iluvbotany4life(Zone 5)

Hey Josh, thanks for the response and the link, very helpful! The containers I'm using are terra cotta pots, 8 inch diameter at the top, 5 inch diameter at bottom, and about 7.5 inches tall. Large drainage hole at the bottom. I just repotted about a month and a half ago, so I know they can't need repotting yet. The soil I'm using is a fast draining soil by miracle grow, labelled as palm and citrus soil, and I also mixed in some regular potting soil, also by miracle grow. The fertilizer I used is a concentrated liquid that comes in a bottle with a dropper, it's by "Shultz". It is 10-15-10. 7 drops per quart of water for indoor plants. I'm almost certain that the yellowing is chlorosis, because the veins are staying green. I think you're right about the browning leaf tips. It gets really dry here in winter, and I know the humidity has to be pretty low in that room. I've heard that the plants like to be misted, but I don't want to end up with fungus problems. I can't imagine that the plants aren't getting enough light. Apart from the fluorescent lights, the plants are in a room with a south facing window, and the room gets very very bright on sunny days.

    Bookmark   December 28, 2010 at 10:20PM
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greenman28 NorCal 7b/8a

Hey!
Thanks for the info!
You're right...Don't Mist! It only increases humidity for a couple seconds, really....
and, as you note, increases the chances of fungus/pests/unsightly leaves.

Also, I'm glad that the plants have plenty of light.
That's good to hear, as it allows us to eliminate one more variable.

How long does it take for the potting soil to dry out (deep in the container)?

I assume that the problem lies with the potting soil, which sounds water retentive.
If the primary ingredient is peat moss, it's almost assuredly staying too moist.
As you know, this can interfere with nutrient delivery and uptake. This is why I hesitate
to recommend fertilization...it could be that there are nutrients in the soil, but
nutrients that are simply unavailable to the plant.

I will tell you that I fertilize my plant with Foliage Pro 9-3-6, which has higher Nitrogen
in relation to the other major nutrients. It also includes all the minor nutrients.
When I fertilize, I also add white vinegar (a capful) to the watering solution -
but I can only recommend this for the potting mix that I'm using. I don't know how it will
affect a soil with different drainage characteristics.

My sister grew a couple Avocados in peat-based soils and the plants declined eventually.
I actually decided to grow an Avocado to see if I could find a way to keep these plants
happy both indoor and out, so that my sister would be able to grow them successfully, too.
I've found that the potting mix makes all the difference - if light and fertilizer are equal.

The taller the plant grows, the more likely it is to discard its lower leaves....
and that's why I prune the main stem and pluck any unsightly leaves.
A bare Avocado stem will resprout leaves as long as the roots are healthy.

Josh

    Bookmark   December 29, 2010 at 12:45AM
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iluvbotany4life(Zone 5)

I'd say it takes a little over a week for the soil to dry out after I've watered it thoroughly. Unfortunately I don't have access to much of a variety of soils for my plants besides what is at the department store. What type of soil do you use for your avocados?

    Bookmark   December 29, 2010 at 12:01PM
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greenman28 NorCal 7b/8a

I use Orchid Bark (fine grade), and then I add Perlite and other types of grit - Pumice, Turface, Quartz gravel.
Pet stores often carry gravel, and some nurseries have Pumice. I have a picture somewhere....

My mix doesn't have any "soil," which is what allows it to drain freely....
plus, you can water it without worry, and you can flush it thoroughly when the
salts (from tap-water, fertilizer, et cetera) begin to accumulate.
With a porous mix, you can eliminate most of the browned leaf-tips.

Josh

    Bookmark   December 29, 2010 at 1:10PM
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jodik_gw

It's very interesting that most container plant issues stem from poorly aerated soils that hold too much moisture at the root ball for too long. They may be convenient, but not really so in the long run.

Josh, that's a beautiful medium you're holding in that photo... extremely similar to what I mix for my plants.

    Bookmark   December 31, 2010 at 4:00AM
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