leaves turning black

Asked November 1, 2014, 11:22 AM EDT

hi , i have an avocado plant which is about 6 month old and it was fine and growing perfect but the older leaves which grown while it was still in the water started to get weak (like loosing color and brown, dry tips).
after few weeks later other leaves started from their tips and sides turning black until all dropped of but trunk is still fine and green. roots are not dark or smelly (root rot) and i only water once its kind of dry. it's happening to my second avocado plant too. i have tried spraying soap water on the leaves too in case its an animal causing this, cutting the infected leaves, separating them from the rest but it doesn't seem to help. i was wondering what could be the cause of this? i live in England if that helps

Outside United States plants houseplants avocado tree avocados horticulture

3 Responses

Dear Gardener,

It is very difficult to diagnose plant issues with one photo. There are a couple of possibilities for the symptoms you describe, but the primary cause is usually too much moisture. While you limit the frequency, check the drainage too. The drainage should be below the pot, not in it. That is, the pot should contain only your plant and potting soil. The pot should have drainage holes on the bottom to release excess water. And very importantly, the pot should be raised above the drain dish so it is not sitting in the excess water. Set the pot on some small stones, beads, etc. to create the space. Then poke your finger into the top half-inch of soil before watering each time, to see if it feels dry at that depth. If so, it's time to water.

Another possibility is a pest, however, this is unlikely if you planted your avocado from seed. You can check this according to this article:
http://plantingpinellas.blogspot.ca/2010/08/avocado-lace-bug.html

As a last suggestion, make sure your plants have sufficient bright light. Fruiting tropical plants in particular need more than your average house plant. If the sun exposure is low, you may need to supplement with a broad-spectrum florescent bulb, or one warm and one cool bulb.

Dear Lynne Marie S

Thank you for your reply, i have made a mix using compost, top garden soil and very small stones to make sure it is well drained mix and each time before i water i use wooden skewer to check all the depth if it is still wet or even damp. the roots are looking healthy and there is no signs off root rot( weak, fragile, discolored or smelly) so i am really confused.
once I've noticed this problem starting i have changed the soil but it seems like its an unstoppable process regardless of what i do.
how can i cure/stop it?
here are some more pics


Hi. Your question got passed along for more help.

First, Lynne was spot on with her assessment of the most frequent causes for the leaf damage in your photos -- soil or disease. Most indoor avocado trees die from too frequent watering. But avocadoes also have specific needs, so lets address some of those.

You say you have changed out the soil - but have you change other conditions too? Avocadoes are very salt intolerant. Do you have a water softener? Do you live in an area of hard water? What type of water are you using when you water the plant? Signs of salt in the water would have been light colored crusts forming on top of the soil or pot rim. Since you changed out the soil, did you see that before or on your other plants?

Also, there is no indication where you live - just outside the U.S. The tree may be naturally going dormant for the winter because of lack of bright light. If so, stop watering and fertilizing until the new growth emerges. Dormancy makes it drop all leaves and overwinter as a bare stem. New growth starts when there is sufficient bright light again. Avocadoes need very bright light and window glass and short days may not allow enough light. Also, indoors in winter can be very dry. What you are seeing could be the result of low humidity. It may need to be regularly misted or moisture added to the air.

Some other things you mentioned sometimes have negative effects on avocadoes. Use of soil from the garden could introduce pathogens. Soil fungus can infect the root system. Did you sterilize the garden soil and compost before mixing? Also, plastic pots seem to impact avocadoes, and the recommended type is clay.

Some further notes: I see you appear to be growing it as one tall lanky stem with a support stick. Houseplant avocadoes benefit greatly from repeat pruning to keep them short and bushy -- unless you specifically want it to be tall and lanky. It may now be too tall to prune back, since that should have started when it was only 6-12 inches tall.

Here is some info from the folks who know avocadoes best -- the California Avocado Growers. This is their info for growing them indoors:

http://www.californiaavocado.com/grow-your-own-avocado-tree/

Hope that helps some. The symptoms you describe indicate some type of plant stress, but finding the cause is not always easy. Good luck.