What i grow in my steep, deep unmowable ditch is lysamchia nummalaria aka creeping jenny. Stays flat, spreads nicely, but is easy to pull if it gets out of bounds. Little yellow flowers. Can handle full sun, and periodic flooding. It will look rough during a drought, but should bounce back. Comes in plain green or hot chartreuse. It stay flush with the ground- so now mowing, trimming or other maintenance. If you have a barrier of some sort, you could consider mint, but be aware it's very invasive if there isn't a driveway or something solid like that to stop its spread. There's also a fairly pretty creeping charlie that is variegated that works well. It also can stand flooding. I also encourage wild violets in my ditch. Anything that's green, stays low and doesn't need trimmed or mowed is welcome. Grass is not.

The plants you mention specifically tend to be susceptible to root rotting pathogens when irrigated during the growing season. They have adapted themselves to soils that are dry when warm and cool when damp, conditions that are not favorable to soil fungi. They avoid infection by living in soils that don't support high populations of pathogens. When planted in soils that do support high populations of pathogens, then these plants are in trouble as they don't seem to have other methods of resisting infection. I don't know about other dryland plants. I suspect it varies by species and by ecoregion of origin, but maybe not. I know that rare plant conservation efforts in Australia are complicated by the introduction of Phytophthora cinnamomi, and that native plants growing in well drained soils are less subject to infection than those growing in soils that are subject to waterlogging during periods of heavy rain. These plants can be wiped out by the pathogen, causing local extinctions and changes in distribution and abundance. So it could be that many dryland plants are susceptible to root rot when irrigated during their normal dry season. Those are my thoughts on the subject. It would be very interesting to see how your plants do over the years.

I read that those lilies were brought over by the colonists and spread by rizome rather than seed, so each plant we see is actually a part of those original lily plants from centuries ago. Anyone else ever heard of this?

Yes drainage pipe. I'm just wanting something to mask the fence I guess. I thought the roses would be just beautiful but I'm thinking anything really green will look beautiful as well. Something that won't damage the fence to where it would need a sooner replacement and something that will keep my husband from worrying. Someone on an ajoining street filled in their backyard ditch so that started to make others yards flood so they had to install the drainage pipes. I of course do not want to do anything to mess up the "flow" - We are in Dickinson, TX - Just had a ton of rain and the ditch did not even hold any water in it.