Link is to info on tulips; from the National Park Service, which is responsible for many local historic gardens. I did notice they say they buy new bulbs every year, so as to have the best possible display. The DC area has mostly clay soil and is not well-suited for maintaining tulips.

The white could have been wisteria although it's just a bit early for most wisterias, or it could have been paulonia [which does come in white as well as the more common purple/lavenders].

The tree with white fringe-like bloom has me stumped. Could it possibly have been a pear or plum that had had the larger petals blown off?? I did notice some local [Fairfax] pear trees which gave that impression due to recent high winds - if I hadn't already been quite familiar with those particular trees, I would have thought they were something else entirely! OTOH, local mimosas have been in bloom; mostly they are a true pink, but they do pale considerably as the blooms fade out; the blossoms could certainly be described as feathery.

Here is a link that might be useful: NPS tulips

You hit the nail on the head with your discription of the tree with "fringe-like blooms." It's common name is Fringe Tree. Beautiful and fragrant, it makes a nice addition to a landscape. Here's a link to NCSU's fact sheet on it.

Here is a link that might be useful: Fringe Tree facts