Drying out.
In a pot or the ground?
Has it been hot? Perhaps santana conditions?

Santa Ana winds, heat, and lack of water.
Mike

My Japanese (red) maple does this every year (all leaves turn brown in about June/ july), has done it for 10 years, even in 2 different spots in the garden. Yet the tree comes back in the spring appearing healthy. I presume it's just too hot & dry here (Palo Alto area) It's 90 degrees today.

I've been trying to determine if this edge-browning of the leaves is natural for our maple. My BF says it is and "it's always done that," but I say there's something wrong with the tree. We live in the east Bay Area. Summers from 85-105 degrees daytime temps. The tree gets a good deal of afternoon sun moderated by the house right next door. I have the irrigation system set to water for 8 mins every morning before sun gets too high. The tree is surrounded by Heaven's Breath ground-cover. Is it too little water? Is the Heaven's Breath "stealing" the tree's water? (probably a silly question!) Or is it just too hot here?

8 minutes of water, even on a daily basis, is nowhere near a sufficient quantity for a tree of any significant size. All that does is tickle the surface of the soil. What you want to accomplish is to have the water penetrate the soil down to a depth of at least 8-10" and depending on soil conditions, that could take as long as 30-45 minutes.

It is always far better for the plants to water deeply when necessary but not all that often. You may only need to water once or twice a week as long as the water is able to penetrate to a proper depth. Rather than your pop-up irrigation system, it would be preferable to use just the hose on a slow trickle at the root zone of the tree.

You may have detected my displeasure with an automated irrigation system :-)) I detest these things!! They are fine for lawns (again, that few minutes daily routine is far from ideal) but they wreak havoc on trees and shrubs and not even great for many perennials. They are seldom ever programmed correctly and they tend to deliver water on the foliage, never a good thing. I would strongly urge you to have your automated system modified to accommodate drip emitters for any planting beds and then reprogram for an appropriate amount of time.