It's always interesting to research the properties of various local "weeds" to see if they serve any function.  Scarlet Pimpernel and Crane's Bill Geranium are everywhere right now (probably in your garden too), and are both pretty plants when they're young -- one has tiny orange blossoms, and the other has tiny pink ones.  Here's what I've been able to find out about them (Plants for a Future is a great website, and of course wikipedia as well, which has pictures.)  It's amazing how much botanical power is contained in these tiny, overlooked plants.
 
I haven't been able to determine yet if the flowers and nectar are used by local insects or birds.
 
Happy Gardening,
Linda
 

SCARLET PIMPERNEL, Anagallis arvensis. See http://en.wikipedia.org/wiki/Anagallis_arvensis Uses include: the plant is a barometer of weather pressure and indicator of light soils. Plants For a Future says the leaves may be edible, but cautions that this may not be wise for a variety of reasons. They also discuss the medicinal properties of the plant, which explain in part why it's not wise to eat it: "The scarlet pimpernel was at one time highly regarded as a medicinal herb, especially in the treatment of epilepsy and mental problems…but there is little evidence to support its efficacy and it is no longer recommended for internal use because it contains toxic saponins and cytotoxic cucurbitacins… The whole herb is antitussive, cholagogue, diaphoretic, diuretic, expectorant, nervine, purgative, stimulant and vulnerary… It can be taken internally or applied externally as a poultice… An infusion is used in the treatment of dropsy, skin infections and disorders of the liver and gall bladder…The plant is best harvested in June and can be dried for later use… Use with caution…large doses can cause polyuria and tremor… A homeopathic remedy is made from the plant… It is used internally to treat itchy skins and externally to remove warts."

 

CRANE'S BILL GERANIUM. Geranium molle & G. rotundifolium. Tiny pink flower. Whorl of circular palmate leaves. Pretty when small but becomes large, seedy, weedy. http://en.wikipedia.org/wiki/Geranium_molle  Historically reputed to have medicinal benefits. Also, Plants For a Future website says this "plant is considered to be anodyne, astringent and vulnerary."