Our house once had a meticulously manicured series of garden beds full of thirsty and fussy plants. It has been watered and periodically cleared but otherwise left alone by us and the prior owners. We want to start replacing the beds with native plants and wildflowers. We are reworking one bed now to experiment with wildflowers before we go to working on larger areas (like the whole front lawn). I’ve done a ton of research, but some areas are giving some contradictory advice on a few pieces so I have some questions. For reference we are in USDA Zone 4 and we get a hard frost in early October.
1. Once the soil is clear and we’ve laid down seed, should we do any kind of weed cover?
2. If we do lay down a weed cover, what should it be?
3. Is there a good rule of thumb for know what is a weed and a wildflower?
There is a number of things to keep in mind.
1. After you clear the soil but before you put down seed, it is actually good to cover with either multiple paper bags or black plastic, to effectively "kill" everything, including dormant weed seeds. If you can do it for a couple months that is ideal.
2. Not sure if you mean a physical weed cover (like above mentioned or mulch, or you mean a plant. In general annuals grow faster than perennials so could try first season with annuals and supplement with perennials so there is something to cover the ground while the perennials become established.
3. A weed is just a name for an undesirable plant. Depending on the person, many wildflowers are considered "weeds". It depends on what your intent is for your garden. If you want to promote wildlife, you would want to re-naturalize the piece of land with local, native species (or at least Western hemisphere plants). These are plants that insects as well as other wildlife can eat, reproduce on, and sustain an ecosystem (including songbirds).
Most states have list of what are non-native and/or aggressive plants, so review those to see which are a problem and get rid of them if you see them. Especially when they are little, it may be difficult to distinguish one plant from the next. There are websites like in Dave's garden and plantfinder that can help you identify plants.
Lastly if you live in a HOA they may have regulations about what you do with your front lawn, or possibly local ordinances (height of plants etc) so check that before starting. Alternatively some western states and cities have rebates for creating a drought friendly garden.