You don't say what zone you're in, or if you want annuals or perennials, but I have good luck with woodland poppies. They're blooming now, and will bloom again in late summer.

Currently i am living in Las Vegas.

Maybe you need cut down some branches of the trees...

Here is a link that might be useful: bulk sacks,woven PP fabric

I'd also like to know some ideas as far as good plants for a shaded yard-- I have one bed for veggies and one for flowers, and am having difficulty through trial and error, finding plants that are suitable for my backyard in the spring/summer.
Florally, I tried a generic wildflower mix last year, but only the tall weedy looking flowers came up. I'd like something bold and colorful.
I live in Providence, RI

Here are some shade tollerating plants. Vinca Major and Vinca Minor, Bleeding Heart - Dicentra Spectabilis, Hosta, Bergenia, Forget-me-not, Ferns, Solomon's Seal, Hellebore, Mahonia, Pulmonaria, Azalea.

How is your soil? Sandy?