Looks like its getting burnt to a crisp. When did you plant it? If it doesn't have any roots set up, it's getting blazed with hot sun, and you fertilized it, I think that would cause the burning. There could be something wacky with your soil too.

Here's the

We need to know all of the following in order to make any kind of meaningful comments :-) your geographic location - state and largest big city what kind of tree when was it planted (if you know) usual summer weather and watering practices and as many clear photos as you can manage...the tree as a whole, shots of the branches with dead leaves and close ups of the leaves (front and back) as well. Fwiw, some trees will have assorted leaves dry and brown a bit in summer and also many that will tend to hold their leaves very late into the season and even through winter. Does not necessarily mean the tree is sick or ailing.

how are you applying the fert.. and are you doing it in sun ... looks like fert may have washed down the leaf.. and puddled at leaf ends.. and maybe got burned ... i dont see any doom.. and i surely see no reason to destroy it all ... petunia need to be cut back a couple times during the season... when they start getting leggy ... i see no reason to do it too soon.. just because of a few brown leaf tips ... i also wonder about a cold event.. since you admit you planted too early ... and a minor cold snap.. may have caused what you see .. and its just showing now .... it never hurts to tell us where you are .. big city name ... zone alone is not good enough ... water when the pot needs water ... which in cool spring should not be very often ... you might be overwatering ... insert finger.. and FIND OUT ... and water when it needs it ... come the heat of summer.. more water will probably be needed ... but not right now ... also.. i see some seed pods forming.. you need to deadhead the pet's frequently ... to keep bloom going... ken