What’s wrong with our Maple tree?

Question: We planted an autumn blaze maple tree May 2020. The first 3 years it’s been happy, except for this year. The leaves have stayed yellow instead of the usual green and a few branches have no leaves. It’s watered by irrigation system, except in winter when we water it once as month on warm days if we haven’t had significant snow. We give it iron once a month in summer. Do you have any insight into what it needs or if we need to change our care routine? Thank you so much.

responder: An Ask Extension Expert Replied August 08, 2024, 12:27 PM EDT
response: Hi Jenn,  I'm sorry your maple is having issues. In doing some research we had a similar question come up recently. I'm going to copy the response below related to one issue I see - iron chlorosis. That is typical with our high pH soils. I also think there may be some potential for root rot - why some of the branches are not leafing out and are most likely dead wood. How often and approximately how much is the tree watered via irrigation during the growing season (not winter)? With the tree being established now (3 years old), it does not need to be watered that frequently. In general, the autumn blaze maple is drought tolerant and if it gets too much water, the roots start to rot. It also prefers a well-draining soil for the same reasons. Best practice for trees is to water infrequently but deep. That would require you to adjust the irrigation accordingly for an established tree. You may want to consider reducing water frequency. That can also exacerbate the iron deficiency as well.  See below for some options related to iron chlorosis. Autumn Blaze Maple does suffer some from iron chlorosis. We are including 2 CSU documents: 1) CMG Garden Notes #1733: Iron Chlorosis of Woody Plants and 2) Fall & Winter Watering #7.211. Dr O'Connor's response: Sadly, many maples suffer from our soils that are high in pH (not necessarily because our soils are clay). A pH above 7.0 leads to a general unavailability in iron because the iron converts into a form unavailable to plants. Our soils tend to have a lot of iron, but the high pH restricts the uptake of iron by the plant.  You can do a couple different things to treat your Autumn Blaze maple suffering from chlorosis:  1. You can apply a foliar spray of iron to the leaves. This is a one-year treatment, but is inexpensive. If done well, I've heard from people that it may last for two seasons. You can use any chelated iron product (like EDTA) and you would mix the iron in a sprayer and spray the foliage. This would be done after the trees have leafed out (doing it now wouldn't be advised, since we're towards the end of the season).  2. You can do trunk injections of iron. While this is effective, I hesitate to recommend this, as someone will bore (small) holes into the base of the trunk, which does cause a wound. I don't like adding wounds/stress to our trees which tend to be already stressed from our environment. But this is an option and should be done by a certified arborist--there are a few in the area that do these treatments. They may apply the iron sulfate you've mentioned, but I've seen trees lose their leaves as a result of the injection. A better product would be to use an iron chelate with EDDHA or EDMA. This treatment can last two seasons.  3. The third option is to apply iron chelate (again EDDHA or EDMA) to the area at the base of the tree by mixing the iron in a bucket and pouring it at the base. You will need to pull back any mulch and/or remove any turf growing near the trunk. Timing for this would be as the leaves are emerging in spring, BUT there has to be good water uptake, so make sure the tree is well watered. This may last two growing seasons.  https://cmg.extension.colostate.edu/Gardennotes/223.pdf https://extension.colostate.edu/topic-areas/yard-garden/fall-and-winter-watering-7-211/ I hope this helps! Good luck.

responder: The Question Asker Replied August 09, 2024, 9:55 AM EDT
response: Thank you for the valuable information! In response, I have a few questions.  1. You suspect root rot. Is our tree salvageable or will it inevitably die?   2. If it’s salvageable, exactly how much less should we water it? Currently we water via auto irrigation every other day for 30 min with 3 adjustable spray heads. Could we just water it once a week with a hose for like 20 min? Is that too little? What do you suggest?  3. Can you clarify the iron chelate (third option) frequency you suggested? The Tree Farm have us applying it every month from May to Sept, but did you really say only once every 2 years in the spring when leaves emerge? That’s a huge difference! Please clarify.   Thanks again!  Jenn   On Thu, Aug 8, 2024 at 10:27 AM Ask Extension <<personal data hidden>> wrote:

responder: An Ask Extension Expert Replied August 16, 2024, 1:55 PM EDT
response: Good morning, Jenn.  I hope that you are finding this information helpful. Below are a few thoughts regarding your follow-on questions.  1. You suspect root rot. Is our tree salvageable or will it inevitably die?   As noted, there may be some potential for root rot, however, this is not a definitive diagnosis and there may be other causes. It's likely worth trying the actions from Dr. O'Connor mentioned above.  2. If it’s salvageable, exactly how much less should we water it? Currently we water via auto irrigation every other day for 30 min with 3 adjustable spray heads. Could we just water it once a week with a hose for like 20 min? Is that too little? What do you suggest?  The key information to consider is how much water (gallons) over what period of time specific plants need and compare that to what you're actually providing (i.e., since sprinkler heads can vary a lot from <1 Gallon per minute up to several gallons, it's safest to actually measure the gallons provided.)   Another key point: we recommend using drip irrigation under the mulch to ensure the most water to the roots of the tree (otherwise the mulch can absorb much of the water) and provide the right amount for the specific tree at the current life cycle, in this case the established maple.    Maple trees require a moderate amount of water once established, about 1.5 - 2.0 inches of water every other week which is equivalent to about 8 - 11 gallons every other week. Ideally, you would provide this slowly as recommended using drip irrigation.  This article, Maples in the Landscape, from Utah State University Extension may be helpful in better understanding your maple tree. Below is an excerpt from this article:  IRRIGATION Water newly planted trees regularly to support root  growth and to support the canopy of leaves. Water  should be applied so that the soil is wet to a 12-inch  depth while trees are establishing. Watering  frequency may need to be adjusted based on the soil  texture. Sandy and loamy soils may require water  every two to four days, where heavy clay soils need  to be watered less frequently. Maples require a  moderate amount of water once established (1.5 to  2.0 inches of water every other week once trees  have established an adequate root system, which  can take up to three years depending on tree size).  Planting maples in the turf can lead to problems  associated with excessive water such as root rot,  iron chlorosis, and other diseases.   3. Can you clarify the iron chelate (third option) frequency you suggested? The Tree Farm have us applying it every month from May to Sept, but did you really say only once every 2 years in the spring when leaves emerge? That’s a huge difference! Please clarify.  The form that Dr. O'Conner is recommending above "iron chelate" may be different than the Tree Farm had you use. I am not sure from your original comment what form the iron is from the Tree Farm, but it may not be in a form that the tree can utilize/uptake efficiently or at all in our high pH soil. Also, treating the tree once per month seems too frequent to us.  Mixing the iron chelate with water, as Dr. O'Connor is recommending, and applying it to the base of the tree after pulling away any mulch, will allow for better uptake and therefore not require this treatment as often. Timing of this treatment is also critical according to the above advice (in the spring when the leaves are emerging).  Dr. O'Connor mentioned that "This may last two growing seasons". Be sure to follow the instructions on the label of any treatment product.  I hope this is helpful. Please reach out if there is anything else we can do to assist you with your maple tree.  Sincerely,   Joanne & Tom