You are at the front of a curve of people learning to establish urban meadows. There are challenges, and one is an idea that it can be hands-off for homeowners. It will take regular seasonal maintenance. I will share some publications for you to research further, making a plan for weeding, mowing, and reseeding.
When to mow isn’t an easy answer, but generally do it when the plants you want to seed have done so. Check their seed pods, as I think most desirable annuals have finished their lifecycle, so you can mow now. An added advantage can be reducing wildfire fuel from taller grasses. We have very dry summers, so part of the meadow cycle is late-summer dormancy. It is due more to natural cycles than the amounts of water you provide.
Read this Meadowscaping Handbook. There are many details included. The end section on maintenance references mowing, and also choosing which plants to allow to set seed.
I found this webinar video from WSU Clark County, and think it applies for your meadow, at least in some ways.
My last advice is to find meadows to visit in various times of the year, so you can compare with yours. I think contacting the West and East Multnomah Soil and Water Conservation Districts is a way to find where there are meadows you can see.
Oh, my real last advice is to water your landscape trees, even conifers. Here is a publication from the Oregon Department of Forestry about watering landscape trees.

Thank you for your response. I have found that your recommendations have answered some of my questions. I have the Meadowscaping Handbook, but haven’t found it specific enough for many of my questions. 

I was just in a training session today about eco-lawns, which isn't the same as what you are dealing with because they are kept mowed short, but it is clear that there isn't firm science-based literature answering your question about raking.
I'll take a stab with some more information to help you decide. If the plants are perennial, they will likely start to grow some this fall with rains and longer nights. Those plants won't be slimy. They will inhibit seeds sprouting. That's a good thing if the seeds are highly vigorous plants that will out-compete others in your mix. But not so great for your desired seeds.
Raking out dead foliage will create more places for seed/soil contact, so again there's that seed sprouting issue: to encourage or not?
How many insects are overwintering in your matted foliage? Do you have specific ones you are interested in tracking? Things like native bees tend to be in the soil or in shrub stems, so raking should be okay. You can look up the life cycle of those you are most interested in, to see where to look for evidence. I have a friend saving certain stems to be available to bees. Beetles and snails and slugs and earwigs are common in undisturbed garden litter. Greater yellow underwing larva are common in my garden, but that's not a native, and another common name is "climbing cutworm" so it eats too many of my flowers so I don't save those when I find them.
Another thing that happens is that a few strong plants will overtake the others, leaving a limited population within only a year or two. Regular re-seeding with desired plants after weeding out others is a strategy some folks end up doing. In my class, participants were more likely to have given up after a couple of years and grow a different type of landscape instead of maintaining the eco-lawn. Another gardener is going to stick with it, but will water more often to give plants a longer season of bloom. The challenge is real. I searched "meadow garden extension plant succession" to see if one publication really jumped out as appropriate for you. They all look interesting, but there's not an obvious one from the PNW. I hope you'll check out a few articles to see what I mean about how the plants compete and change.
If this was my experiment, I would rake half and keep notes about what happens.
I'm in Washington County, and two places with non-watered open areas to visit are the Tualatin River National Wildlife Refuge and Cooper Mountain Nature Park.
Are you willing to let me copy your photos to share with other Master Gardeners? You have a fantastic experiment underway.

Jackie, thanks for the expansion on my question and the very useful detail you provided. Now that I understand better just how much of an experiment this is, we’ve decided to try a few things.

We’ve divided the space up into three zones (there are probably more than that, but we’ll start here). Zone 3 was just cut back to eliminate the tallest growth and we will leave it and observe. Zone 2 we mow/mulched at a high setting with the mulching mower, thus chopping up some of the thatch, and will observe. Zone 1 we mulch/mowed and then raked. We tried to hand-pull the thatch and it came up so easily that it left bare soil patches. This makes me think that perhaps we didn’t have as big a problem with recurring lawn grass as I thought, so I feel more comfortable leaving that thatch. We’re not going to seed the few open soil patches immediately, because we’re not sure what is currently in that soil. I’m still trying to identify a lot of the plants that came up.

Likewise, I don’t have any particular pollinators that I’m following; just trying to see what shows up. One of my original sources recommended putting down slug inhibitor when we seeded last fall, and I didn’t really see any evidence of slug activity. I can happily live without them!

I like the idea of more frequent watering and will try that. It got so dry so fast this spring that I feel some later plants didn’t get their chance. We had several kinds of lupine for example that grew well but never bloomed. I also look forward to checking out the two park/preserves you suggested.

I will also try to send some photos. They represent the timeline from when the area was a grassy lawn to the present

Excellent plan. I manage an historic cemetery in Dundee, and have visited a few others in Clackamas and Yamhill counties. I just realized those, while often privately owned, are open spaces visitors can see. There’s a wide range of weeds, grasses, invasive plants and natives. Not sure you want a full-blown hobby, but I’m sharing the idea as additional spaces to study.

Thanks for the cemetery idea and for the encouragement. Did any of the photos I tried to send come through?
Sent from my iPhone



I don’t see any photos.