That panorama pic is really small, so here are the separated photos, followed by a pic of where it continues around the house.

continuing around

and around

And where it continues around the house

"We weren't sure how to deal with swale that the builder created around the house, so we just had him put gravel in it, thinking that maybe it could function as a path."

It's too bad that you didn't come here when the issue of dealing with the swale first presented itself. I've got to say that putting gravel in it will rank as one of the worst "solutions" that has shown up on this forum. It doesn't solve problems. It creates them. I say "worst" because it is without genuine purpose. Not only was it expensive to create, it will be costly to fix. If a swale is necessary (as surely it would be here) then there is no reason to start filling it up with material so that its water carrying capacity is reduced. As an analogy, think about how wherever there is curb and gutter along side a road, a swale-like structure is created. The road is crowned so this directs water to flow toward its sides. The curb at the sides contains the water and holds it on the roadway. Therefore, a channel (like a swale) is created along each side of the road. We've all seen what happens in heavy rains. Water can accumulate so quickly and in such volume that in some places, the water will overflow the curb and extend toward the center of the road. In a significant storm, water can span the entire road, blocking it. Now, Imagine filling up the volume of this space (which is created between the crowning of the road and the curb) with gravel. What will happen to the water flow now? It will be immeasurably slowed! The purpose of a swale (like curb and gutter) is to move excess water away QUICKLY ... before it has a chance to build up. The gravel in the swale will negate that possibility.

If the swale was ugly (like a ditch) then the problem was that is was poorly sized and shaped. A low, wide swale can carry as much water as a steep, narrow one. Make it low enough and wide enough and the fact that it is a swale may be nearly impossible to perceive. It could have looked like a normal part of the lawn and be perfectly easy to walk on. (For some reason builders like to build ditches, though.) Grass alone would have been fine for a "path" that was rarely used and not really needed.

Aside from the fact that the water holding capacity of the swale has been reduced (we don't know if or when repercussions will be felt) this gravel creation would likely create problems whenever anything is planted in its vicinity. The most likely plant to have wanted here is grass, but it cannot be installed because doing so would further raise the grade and nullify what is left of the swale. Should a tree be wanted ... well, dig one hole in gravel and it will cure you of wanting to dig any others.

The solution for this is to remove the gravel and reshape the swale to something that is more desirable. (For what to do with all the gravel, maybe you need to build a driveway somewhere on the property...?? )

As far as what to plant on the slope ... if you want a woodsy appearance, replicating that "look" requires planting trees close together (just like what is nearby.) A large cluster of flowering tree (such as redbud) could add a lot of drama at bloom time. Consider that what is planted along the ground as groundcover will be important in terms of maintenance. It would be easier to keep weeds out if you keep it as mulch-only for a couple of years and then add groundcover once the trees are up, running and producing some shade.

Thanks for the response. I take full responsibility for the gravel decision. The builder wanted grass there, but I thought it would look odd and be hard to mow. We needed an immediate decision, so I did a quick search for "swale" on Houzz, and found this picture. I liked the look, so we went with it. But ours isn't really looking anything like that, except in the last picture where it goes around the house. I like it there. I just can't visualize what do do with the lawn and the gravel edge. So far, the water seems to be moving just fine. We have had a few torrential downpours and I haven't noticed a problem with water accumulation. If there is a way to landscape it and make it look nice, we would definitely prefer that option. My husband will kill me if I tell him we have to dig it out.

Regarding the hill planting, I like the idea of planting trees now and then waiting a few years before planting a groundcover. When you say close together, how close? Like on the low end of the spacing recommendation for the tree, or closer?

"My husband will kill me if I tell him we have to dig it out." At least he can have your grave dug while the equipment is there and save a few bucks on that. :-)

It's more common after doing something like this that one just live with it unless it is causing a direct, known, even more expensive problem. You say water seems to be moving fine after some serious rains. If that's the case, then you may be absolved of that consequence. I say "may" because the real test has probably not rained yet. As far as landscaping to make it look better, when you install sod it's going to look better. When you install groundcover it's going to look better. Maintaining the edges of each so they coincide with the strip is going to be better than allowing them to grow all ragged. Whatever the groundcover turns out to be, you could let it grow and spread to cover up the gravel so it wouldn't be noticeable, but that will reduce the swale's water carrying capacity somewhat more.

As far as how far apart to plant the trees ... measure some distances in the wooded areas that agree with what you are trying to accomplish. 6' to 12' maybe. A more conventional landscape approach would be to install trees in a double row where they are about 20' on center in the row and where the rows are about 10' apart from one another, and staggered so that the tree location is offset in the next row. It would not emulate nature, but be suggestive of it, and look more orderly and tidy. (I'm guessing at the numbers since there is no scale plan to see. It could be three rows and spacing could be adjusted according to real life conditions. For a wooded-ish look, figure on allotting 100 to 150 s.f. per tree. The intent is to create a solid, contiguous foliage canopy.