I know this is an elementary question but I'm just wondering. We have a patch of yard that we've been trying to fill up. Still a lot of open space. I was thinking maybe mix various wildflower seeds and randomly strewing them. I'm envisioning a pretty mix of colors and shapes. Do the pre-mixed seed packets and/or my own mix work? Do they bloom well? Also, if I plant them now (Memorial Day in NJ) would they bloom this summer, or not 'til next year?
Yes you can make your own WF mix. I do it all the time to fill in spots. I have several wildflower/native plots/beds and I have color in them from April to almost November. I would stay away from many of those pre-mix packets you see in the Big Box stores, my experience is they have very little wildflower seed and are mostly annuals that are not wildflowers and don't reseed very well. Now is not the time to plant a "wildflower" garden. Many wildflowers need cold stratification to germ and the best time to seed them is in the late fall just before the ground freezes. Also, there are many wildflowers that will take two years growth before they bloom.
What you can do now is plant a mix of annual seeds that will germinate and bloom this year and then seed wildflower mix in the fall. Often, wildflower mixes from reputable dealers will have a mix of annuals and perennials so you have something other than just green until all the wildflowers mature and bloom.
If you really want a wildflower/native area you need to spend a little time reading some info from companies that specialize in wildflowers. Here are two of the best in my opinion:
Both of these companies have individual seed species available as well as many different seed mixes for almost any condition. They both also have great information on the hows and whys of establishing wildflowers/natives.
Stay away from those companies that are selling wildflower seeds and a million other types of plants as well. I have bought seed from some of them and most contained seed of very pretty plants in their mixes but many of those were invasive and non-natives. I am still pulling their "weeds" out of my wildflower plots six years after I unfortunately bought a mix from one of those companies.
A couple of other notes on wildflowers. You can spike the mixes if you have a favorite flower or two, just buy some seed of your favorite and mix it in.
If you really want to learn more about wildflowers (particularly identifying them at various stages) take a small sample of seed from the mix and use various resources to ID each of the seed types. Keep the individual species separate and sow them separately and treat appropriately for each species (temp and stratification). Then as they germinate and grow you will have a good reference for what you see growing in your plot. You will also have some plants that will be ahead of what you sowed and some of them will bloom the first season. If you want to do this I would recommend you try to time things to germinate in January so you have time to get good growth before transplanting. For example, if one of the species needs 60 days cold stratification, be sure and start the cold treatment in November to bring up to germination temp in January. If you decide to do this, don't do it with individual seeds, use 10-20 seeds for each species and sow them in small pots (2.5 - 4"). Germination will not be 100%, and for some it will be closer to 10% with some seeds having an elongated dormancy. But don't worry, many of these will germinate, just not as quickly as you may be expecting.