It does work as a rooting aid. Is this what you wanted, or did you want to use it on seeds? This is the seed forum.

A book I read ("the new seed starters handbook")says to soak stubborn seeds in it.

Flash,

So, if you don't have any willow trees handy (I don't) could you just use salicylic acid instead?

MM

If you do a web search, there seems to be as many articles stating aspirin is a germination inhibitor as articles saying it improves germination.

Were you thinking of sowing seeds that sometimes prove to be difficult? There may a more standard method someone here could help you with....

morz8,

I am interested in willow tea both to promote root formation on soft cuttings and to help stimulate germination of some old seed.

MM

Maineman, willow tea does promote root formation, but not necessarily better than commercial preparations. There are many articles available like the link (credible author), and the 'recipe' there for making willow water is the same as I've seen demonstrated by Dan at Heronswood - overnight hot water simmer.

Though many seeds can keep for years (some for even hundreds of years), most will remain viable for approx three, some species much less. Seeds that are no longer viable will not germinate no matter what you do to them.
I don't find any credible evidence of willow tea promoting germination...are these seeds that you can't replace with fresher(?) because if not, of course it never hurts to try. More conventional methods though are hot water soak or extended water soaks, moist chills, acid treatment (or hydrogen peroxide soaks)....I've even seen written by one propagator I greatly respect that the only way he could get a particular seed to germinate was to soak in gasoline. It must not have been a plant I was tempted to grow because now I couldn't tell you what the seed was; I only remember mention of the method :)

Here is a link that might be useful: Willow

Salicylic acid is known to block synthesis of abscisic acid (the reverse is also true, its pretty complicated). Abscisic acid is involved in producing seed dormancy and also in promoting seed germination. It may be that supression of abscisic acid in some seeds removes a dormancy while suppression in others prevents germination. There is certainly every reason to believe that there will be some effect.

Two weeks ago, my father (who lives in AR) showed me the difference in two sets of okra plants resulting from some seeds being soaked in gasoline and the others in just water.

The ones soaked in gasoline looked like they had been planted a week earlier!