wildflowers if your soil is bad depleted it would be a good idea to enrich your soil first with compost and manures instead of depending solely on plants to enrich it for you. that said many so called weeds even things like burdock, dandelions, and yes even poke salad which is high in iron can be chopped and dropped to add many minerals & nutes to the soil while providing mulch at the same time for your plants. just be sure to chop before they go to seed if you don't want tons of "weeds" at the base of your plants.
dynamic nutrient accumulator are called such because they often accumulate a lot of 1 or 2 key nutes or minerals. Diversity is more important than a monoculture of 2 or 3 nutrient accumulators here are some great plants to add to your landscape if you don't have them yet. Many members have already spoken about cover crops and other things that are good to add but perennial shrubs, and trees wasn't mentioned too often. You live in the same zone as me so off the top of my head you can grow Bee Balm, goumis, mulberries, Meadowsweet, sea buckthorn, Siberian Pea Shrub, and honey locust all of which are great for the soil in many different aspects. There are also many grasses like switchgrass, & Indian grass that increase glomalin levels and arbuscular mycorrhizal fungi thus helping surrounding plants better take up the nutrients that are available in the soil. Hope this helps.
