What to plant in bottom of swale

I'm a total newbie here and would like some advice on what to plant in the bottom of my swale.
I dug a swale with a berm on flattish ground to capture rainwater off of my roof. I put berms on either side of the swale and have planted some fruit trees so far. What would you plant next both on the berms and most importantly, in the the swale. I have some comfrey ordered, and plan to put some elderberries close to the bottom of the swale, but other than that I have no idea where to start. I am in zone 4a in Saskatchewan, Canada. I don't want mud in the bottom of the swale but want something that can withstand our winters, some traffic, and water.

Jessi, I have the same question!

Though, about 16 years ago I dug a swale at the back-end of my property for a non-permaculture purpose and haven't planted anything either in the bottom or on the top.
Interestingly, along the bottom have grown up a bunch of volunteer trees.  Guessing birds dropped the seeds and they've spread from there.
Figure they're my firewood storage "on the hoof" so to speak.

Could we see a picture? I hope that the berms were setup in a way to direct the cold air downhill instead of trapping it.

Do you get a good amount of rain? If so, maybe watercress would work. It is tasty and a dynamic accumulator species. I have not planted any yet, but just got some seeds. It can go 'weedy' in areas, this means more mulch and also more work.

Maybe a clover mix would work. Perhaps you could slash it down a couple times each year and throw if on your berms.

Let us know what you go with and any other questions, what you would do differently next time, ect...

Depending on how wet it is at the bottom, blueberries could be a good choice, as most varieties will enjoy the moist area there high in organic matter.

Fruit trees are great for the top or mid slope up the berm depending on how wet or dry your climate is. Herbs can be great for the very top too, with veggies along the sides of the berm down to near the bottom.

There are varieties of rice that can handle flooding, but are ok growing without it. Depending on how the waterflow varies, that might be something to look at.

If there's constant moisture, cattails, watercress, or marshmallow might work.