I just noticed my in-ground tree developed black spots along the edge of its leaves. This is its first year in ground. Is this an indication of some mineral deficiency? Is there anything I can do? Thanks in advance for any help.

Hi,
For me it is a global weakness - missing of fertilizer or too shady or too rainy spot for some time.
So is the tree in a shady spot ? If not fertilize then :) - that tree needs to grow new leaves to keep going .

Add water.

Probably not related to your problem but my black jack started from a cutting this year had black on their leaves similar but much more (sorry no photo it happened so fast).  In just a few days the leaves crumpled and died.  Even the stem looked dried out. 

I transplanted to new container and soil and put it aside figuring it was dead anyway.  Pleasantly surprised to see 2 new shoots with 2 leaves each grow from below albeit with pale leaves.  The top of the stem looks dead.  Will cut that off once the plant gets stronger.

Thank you so much for the advice, jdsfrance, Jon, and Pino. I will keep it watered regularly. I will also fertilize it to see how it responds.

Your strawberries look happy so my guess is that the ph is a little low. After a quick search I confirmed that Vancouver does tend to have acidic soil. So in addition to fertilizer spread a cup of dolomitic lime around the tree monthly. A top dressing of compost will also work wonders...  Be cautious watering, not sure if Jon knew you are in the PNW.

p.s. I would do a quick soil test with a ph indicator first. 

Generally leaf symptoms are a "trailing indicator", meaning they tell you something about what happened in the past. For instance, is they turn brown, dry up and curl up, they were probably underwatered and too hot at some point in the recent past. If the stress was less, then perhaps a portion of a leaf will show signs; maybe half will turn brown. Small black/brown spots can be a symptom of of stress, usually underwatering. In the Fall they are more likely a sign of age and coming dormancy, along with turning yellow.

By comparison, wilted leaves are "current indicator": a sign of insufficient water. This could be due to underwatering, over heating, or perhaps low humidity on a young leaf that transpires more moisture than it can take in. It is telling you about current conditions.

Generally, you have to have some sort of additional information to correctly assess what the leaf is telling you. Did you recently miss a watering day, was the weather suddenly hotter or dryer than usual, etc.

Yellow leaves in the early part of the season might indicate lack of fertilizer, or leaves that are being shaded out. In the fall they indicate the onset of dormancy. They look the same, but additional information helps determine the correct reason.

Jon - thanks for the detailed explanation. I live in Vancouver, where it rains a lot. Usually I don't worry about watering an in-ground tree, assuming it will get enough water from rain. I have in fact never watered it since planting it in ground. Maybe it's susceptible to lack of water during a dry spell, especially because it usually gets plenty of water from rain. Brent - thank you for noticing my strawberry. Yes, our soil is usually pretty acidic. We always have a moss problem in lawn. I will follow your advice.