They were big decorations so maybe for the office buildings or big stores, not for the private houses. These decorations are placed in pairs at the entrance of the building or in front of the house, usually after Christmas day until 7th January. So when we see them we know... the new year is approaching.
(In front of some office building)
This kind of traditional New Year decoration is usually made with pine and bamboo, sometimes with branches of ume(Japanese apricot) and its designs vary very much depending on the provinces. I think, it's considered as a place where the new year deity would visit and dwell in, they would bring the family health and prosperity for the new year so each house and shop needs Kadomatsu to welcome them. (So when we see the house with no decoration on New Years Day we think they might be in mourning for someone.)
variation of New Year decorations.