Oh good! It didn't seem like it to me because your trees looked so drastically different, sorry about that.
Hah, I used that same reference picture to churn up an example, but reconsidered posting it since it wouldn't have really helped with the stuff I wrote. Good old google!
Alright, so right now I'll come out and tell you not to worry about style yet. Just try to reconstruct what you see for now. Lemme suggest something that you may or may not be used to doing; draw a tree's silhouette using only negative space. I'd say that you will want to try an oak tree or something that has a more dense leaf structure than a palm tree. Just try to pick out the shapes the sky makes around the tree and through its leaves. In fact, for all of the trees you draw,
don't try to draw a tree; draw only the shapes and lines you see that make up the tree.
I'm liking your new tree. Although I still feel like the leaves don't have quite enough contrast. By contrast I do not mean the value of the shades you've chosen; they're plenty contrasting enough in that respect. Look at that palm tree reference you posted, and notice how the shades are distributed.
This is what I see:
The leaves are actually much more isolated in terms of value because some of the leaves are in shadow with only the ambient light from the sky to keep them colorful, while others are getting hit full on by the sun. Leaves will never ever all have the same about of sunlight hitting them, not even close to that actually. Try to distribute your shades accordingly, and refrain from using all of your shades for each leaf or leaf cluster. This is always best to work out in the very early stages of your art since the more work you put into something the more attached you get to it, and it's really hard to get it all right your first try. I did a lot of reworking just for that little example.
Another thing to remember is that you don't wanna make a straight color ramp of green and a straight ramp of brown for the leaves and trunk respectively. In your reference picture there's a lot of blue and yellow in its leaves, and it will make your art pop out and tell everyone, "I'm a tree!" if you can find the actual colors that make it up. Generally, things slowly hint towards yellow as they get lighter and tint towards blue as they get darker because of the sun and sky. Or, if you're doing a piece with different lighting, then just remember that warmer = lighter colors and darker = cooler colors. Just remember that for a guideline though. Just play around with hue shifting as we call it and find something that you like to use.
Here are the colors I see in the trunk and leaves:
Also notice how I began working in the details. What I did was try to emulate the actual leaf structure by first making those light lines through the middles where I saw them on the reference picture. Then I drew a couple more lines out from the middle lines and within the silhouettes I created earlier, and finally drew some of the leaves sticking out of the big blob of color, and made little indentations where the leaves weren't. It was super easy to get the leaves worked in that way than just muscling through it all all at once.
That's the reason I said to observe meticulously, and really study how a tree or anything works. Just remember that details aren't very welcome in a piece until you've got the basic idea down really nicely because theres always major structure issues that need to be fixed after the first couple tries, and it's really easy to fix them without any details.
So yeah, don't draw a tree, don't draw tree colors, observe the shapes, and let the image itself tell us it's a tree.