What To Do with Ash Trees That Have Scorched Leaves

 Q. I think you addressed this not too long ago but I give your Saturday articles to my neighbor so I’m not sure what you said. The attached photos show two trees the builder put in my front yard two years ago.  I think they are Texas Ash?

 Ash trees with leaf scorch. Most likely this microclimate in the landscape is too hot for this tree.

Aha. This is a hot location if it is south or west facing. The irrigated area under this ash canopy is too small. Expand the area and apply water to a wider area.

I have three yellow emitters and now water these trees twice per week for 15 minutes.  (I can’t remember how many gallons the yellow ones due in an hour)!

A. Ash trees don’t like the heat all that much. All of them including Arizona ash. So surrounded by rock (even though it is five feet away from the trunk) is not the best thing for it. The roots of this tree can't keep up with the demand by this tree for more water. The main reason you are seeing the leaves burning on the outside (leaf scorch) is either because the soil needs improvement or the soil is staying too wet or both.

If you can make that basin covered in wood chips about three feet wider from the trunk it will help. Rake the rock back, get more scalloped pavers and make it bigger.  Also, the wood chips should be about four inches deep. Keep the wood chips from the tree trunk about six inches.

It helps to put a thin layer of compost on the soil surface under the wood chips. If this is a burden then sprinkle it on the top of the wood chips and water it in with a hose. Mixing it into the hole at planting time should have been done at planting time but some of the less expensive plantings (I have heard rumors of this happening with some “special deals” from nurseries) don’t use much amendment at planting time or not much mixed in the soil or the holes are dug too small or all of the above.

I am not sure how you are watering that tree (one of the ash). There needs to be AT LEAST four drip emitters to that tree at planting time about 12 inches from the trunk and enough water applied to wet the soil 18 inches deep each time you water. After the first couple of days the watering should NEVER be daily. The first couple of days daily watering is okay to get the soil wet and get rid of air bubbles. The soil needs to dry out between irrigations. 

A long piece of rebar or any thin piece of steel can be used to judge how deep the water gets after an irrigation. Shrubs less than 3 feet tall irrigate to 12 inches deep, medium sized shrubs and trees to 10 feet tall irrigate to 18 inches deep, if 20 feet tall then water to 24 inches deep and big trees water 36 inches deep.

Use a four foot piece of rebar from Lowes or Home Depot to judge if watering is deep enough. If not, water more minutes or add drip emitters or get some that deliver more water until it gets that deep.

In mid summer three times a week is plenty if they are all alone and no other plants for the ash tree roots to get water from. Right now once or maybe twice a week is plenty. In about two or three years you better add more drip emitters in another ring out past these emitters about 18 inches away.