And just because the silks have emerged, it doesn't mean that they are ready for pollination. The silks can usually be trusted to come into maturity at the same time as the pollen bearing flower, the tassels. Those stigmatic tubes (the silks) must reach a certain stage before a ripened pollen grain can germinate on the surface and set the sperm loose to travel down that tube to the awaiting ovary. Corn and other wind pollinated plants rely on this timing, as well as plenty of climactic cooperation. Regardless, if the female organs haven't ripened, no amount of pollination can make them set fruit.

herman2 I have 5 goji trees, one pair are the same, the other pair, I grew from seed and the other is from somewhere different. All are 5-6' tall and only two flowered and zero fruits in 3 yrs. I am going to give them one more year and then something else will go in.

Hiya Trolip and all, You can pollinate it with anything in the same genus (Cucurbita), but if you save the seeds from the fruit, they will be hybrids between the two types of plants (sometimes fun, sometimes not). Azreno is right: you can collect the pollen from the male blooms and store it in the fridge (dry is best, so ideally in a sealed jar half-filled with flour and the pollen in a small, open envelope or container inside the jar (resting on top of the flour) so the flour can absorb the moisture). It will keep for quite a few weeks that way. I do the same thing all the time with various plants that do the same no-opposite-sex-blooms-open-at-the-same-time thing. Moisture-removing silica gel works better than flour, but flour is a fine substitute for short, quick, storage. Let us know what you do, and how it works out. Take care, Grant

The dabbing you did to the female flower was almost certainly successful. Just a gentle dab or two, here and there, is plenty. I sometimes worry that I'm damaging the female structures with too much agitation, but it all seems to work out OK. I would just suggest a few light dabs are plenty, as long as the male flower is visibly dusty with pollen grains before you start. I don't know if pruning the tip will help. It will certainly encourage the growth of side runners. I would just make sure to cut off any more female flowers. I like to let them open and have their day in the sun just so the bees can have their fun. Hey, if you want the bees to work for you, you've got to provide them with the goods.