What is causing the burnt tips on my avocado tree?

Asked August 19, 2015, 10:06 AM EDT

I have a Fantastic variety of an avocado tree that is currently potted and approx 3' tall. I bought it in March. It has seen decent amounts of growth in the last 6 months. I have it protected from the burning sun and water it once to twice a week depending on rainfall and the heat. I test it before watering by checking at 1 to 2" depth for moisture. I did add fertilizer about a month ago (organic plant food).

I have noticed that the older growth has browning on the tips. It was first noticeable in only one area of the tree. I thought originally, since that side was west facing and gets a bit more direct light in the afternoons, that it was burning the tips. So I rotated the tree to see if that helped. The brown tips are still consistent in that one area, but more and more leaves now have the browning. I believe this damage may fall in line with the "salt/chloride buildup" descriptions and photos I have seen. I've read a few of the online "expert" opinions on how to flush the salt from the roots, but I am not sure which seems more accurate to help or possibly damaging. Before I launch into recovery mode for this tree, I wanted to know if there was a better solution or even another underlying issue that I may have.


Lee County Texas trees and shrubs avocado tree horticulture

8 Responses

I'm impressed with your CSI detective approach.

When symptoms involve leaf tip burn, my first suspicion is a root stress issue (soil moisture levels,..too much or too little; damaged roots, etc.). I would say so with >95% probability.

Are the leaves browning back from the tips inward and/or browning from the sides inward? Could you send a photo or better yet several photos of the damage?

You could have a soil salinity issue but if you just potted the plant last March this would be a rather rapid onset. If you only watered enough to allow very little water to drain out the bottom, this could happen. It's good to "over water" most potted plants when there is a drainage holes(s) as this helps to avoid build up of salts. Have you noticed any salt build up along the upper rim and inside (but above the soil) of the pot. If so flushing the soil mix with several waterings will help to leach out excessive salts.

I definitely recommend against applying gypsum (a very good product but too often recommended as a panacea). Same goes for using vinegar. I like your step by step approach.

Lastly, leaf tip burn back typically does not present on one side of a plant but I cannot rule out circumstances that may cause such.

Please send photos of the whole plant including its surrounding area a well as some reasonable close up photos of the tip burn and I would be glad to review and give my opinion.

William,
Thank you for your reply. I have attached a few photos. It may be an issue of over watering. There are only about 4-5 holes on the bottom of the pot. I may need to add a few more to help with drainage. There are Styrofoam peanuts in the bottom of the pot to help with drainage and weight. I don't typically "over water" to the point of watching water drain out, but I will from now on and on a more scheduled basis (once per week, twice when its hot).
I have not noticed any salt building up on the sides, but will look for it from now on. My husband does not think we have high salt levels in our water. I will see about getting it tested and in the meantime, keep an eye out for any signs on the pot.
I will not take any action until I hear back from you on reviewing these three images. If you need more taken, I will be happy to include those as well.
Thank you!
Mary Pearl

Most of the leaf symptoms would be attributive to root stress issues (eg., soil moisture levels,..too much or too little; damaged roots, salt buildup in soil, etc.) and I suggest maintain a watering schedule as you described. Would be best to have at least some water draining from the bottom each time you water and especially on weekly basis. Just about any water source (well or municipal) will have some salts [typically salts of calcium (Ca2+), magnesium (Mg2+), and sodium (Na+)]. If they are not flushed out, they tend to build up in the potting soil over time. NOTE: your plant otherwise looks healthy; I am assuming that your water is not treated by a water softener...otherwise, I think your leaves would exhibit very severe dieback.

If you would like to get a soil test (costs $10), it would indicate if you have a salinity (high levels of salts) issue as well as your fertility level. Would have to send the soil sample to the Soils Lab at Texas A&M.

We harvested 133 avocados from our tree in the demonstration garden in Carbide Park!!

Thank you so much! I will set the watering schedule and try to keep in mind that I should "flush" it over water until its pouring out each time. I will do a soil sample in the coming weeks.
I cannot WAIT until I get 133 avocados - or maybe even just ONE!
Thank you again!
Mary Pearl

Mary,
We are doing a string of e-mails here!!
I forgot to make one more observation. Judging from the photos you provided, it appears that there is very little distance between the top of the soil mix to the top of the pot. May do more damage than good but see if you can remove some of the very top layer of soil to increase the distance (but do not do any major removal).

This would allow for a greater amount of water to accumulate on the top without overflowing and hence allow for more water to drain through the soil with a single watering. OR, you cold just water several times in a day for a major flushing of salts OR, if you decide to bump up to a larger pot size be sure to allow 3-4 inches space between the top of the soil mix to to top of the pot. It's hard to provide a flushing watering if there is not enough space to allow water to "pool" onto the top of the soil mix.
If this does not make sense, let me know and we add another string of exchanges. :)

Thanks so much William!
We had some high winds yesterday that knocked the pot over, so I had 'help' removing the top few inches of soil from the pot! Ha! By the time I got it stood back up and as much soil without debris replaced from the ground, i had a nice 2-3" lip around the pot with space to do just what you suggested. I did loose one small branch (4-6 leaves) from the topple. It will be secured mire now to keep it from doing that again!!
I have done one full water flushing after your suggestion. It was pouring out of the bottom of the pot for a bit. I will keep the schedule and let the water 'pool' from now on.
Thank you so much again for all of your help and guidance. I am thrilled about my avocado tree and it's growth. I have it lined up next to my seed spouted avocados, a Bastrop pine tree (i think a lob-lobby or longleaf pine), my Aggie Century Tree seedlind (live oak), a rescued nectarine sprout, and a few dying avocado seed spouts.

Mary,
Good to hear.
Be aware that avocados can attain considerable (45-60 feet) when round in the ground. However and as with many types of fruit trees, they can be container grown, aka as a quasi bonsai.
We posted some photos of our avacodo tree in our demo garden to our MG Facebook page (will have to scroll down a bit to the July 25 post:
https://www.facebook.com/pages/Galveston-County-Master-Gardeners/220088841395231

They will become top heavy so you might install a clothes-line like wire to brace the top growth from blowing over in a high wind (and we certainly got that yesterday).

I'll bring chips if I get an invitation to share a bowl of guacamole made from the first harvest (just kidding) as I believe you will get there !!!

That's amazing! I need to come and see that garden in action some day.
And I will definitely send you the first invite for some guacamole!
Thank you again for your help!
Mary Pearl