The yellow herbs of summer: Goldenrod.
Good for respiratory problems, and good as a herbal oil, too.
Pick the flowering tops (of Solidago virgaurea) in late summer (through fall) on meadows, off the clearcuts of yester-yester-yesteryear (or thereabouts), or at the edges of forests. (The larger Solidago canadensis and gigantea will take over open areas if given a chance, and they flower later than the smaller virgaurea - shrug). In addition to the yellow-flowering goldenrods you can also pick the more or less purple-flowering fall-flowering asters: go for all species which are spicy in their top leaves.
Drying solidago flowers will fall apart into yellowish-grey fluff - don't throw those out, use them, they're normal.
Oil: Make an oil from the dried flowers, see instructions under SJW. Excellent for muscle aches (sorry -- I forget whom I should thank for that tidbit), one lady ran to my stand half a year after she'd bought one salve to try it out - and bought half a dozen. She was very pleased that I still had that goldenrod salve. (I sell my salves at the local useful plant society's market days, three times a year).
This is a dry herb oil: you have to see to it that you don't get water into your oil at any stage of your oilmaking. That means that you wipe the underside of your waterbath bowl before you pour your oil into the cheesecloth-draped straining bowl, and it also means that you only use dry utensils, that you wipe down things instead of washing them in between (don't use cloth to wipe oily things, use paper towels: it's next to impossible to get oil out of cloth), and so on.
Tea: While solidago of course is very good for urinary tract infections (and diuretic, too), you can also use it for variously mild lung grunges (thanks jim!). Make a tea (for instructions, see SJW), and drink 2-3 cups a day for hayfever, coughs, sore throats and asthma (and similar).
Goldenrod is diuretic. Don't drink the tea in the evenings, unless you want to get up to pee in the middle of the night -- or get a nice warm feeling for a short while. After which it's time to change the sheets.