John S said
It is possible to grow kumquats in the Willamette Valley. I have known a guy here who grew them in a large half barrel on a very dwarfing rootstock.  He had to bring it inside the garage even here, zone 9a. Pips NYT
I have been doing that.  They are flowering but the fruits have been falling off. I don't know why.
John S
PDX OR  

Hi John,

Kumquats usually drop their little fruits if they get stressed, especially from uneven watering or sudden temperature changes. Keeping the soil moisture steady, giving them plenty of sun, and a light dose of citrus fertilizer should help them hold their fruit better.