There's a particular evening, usually a week or so before the tree even goes up, when the house still feels bare and a little flat, and bringing out a box of green pieces, the deep pine sprigs, the glass baubles with that bottle green shine, changes the whole mood of a room before a single light is plugged in. That's when green decorations earn their place, not on the big day itself but in the quiet lead up to it.
The difference between a green decoration that looks rich and one that looks like a cheap party favor usually comes down to materials and finish. Real glass baubles hold color in a way plastic never quite manages, there's a depth to a hand blown green glass ornament that a molded plastic one just can't fake, even a good one. Velvet ribbon and bows in forest or bottle green behave completely differently to the shiny acetate stuff, they absorb light instead of bouncing it back, which is why they look expensive even when they aren't. With faux greenery, check the construction before you buy, not after. Pull a branch gently and see if the wire core holds its shape or just flops back. Cheap garlands shed needles within a week and look thin and sad by the second week of December, while a well made one with a decent wire frame can be bent into shape year after year and still look full.
For scale, measure before you buy rather than guessing from a photo online. A wreath that looks generous on a screen can look like a small plate on a full sized front door, and a tabletop tree in deep green looks lost on a long dining table that needs something at both ends. Walk the space with a tape measure and think about sightlines from where people actually sit, not just where the thing will stand.
Where green decorations fall short is in rooms that already lean heavily green, sage walls, olive sofas, a lot of houseplants, where another layer of green on top just goes muddy and the eye has nowhere to rest. In those rooms it's worth pulling in gold, cream or a warm red instead and letting green stay as an accent rather than the whole story. Green also reads differently depending on the finish of your lighting, warm bulbs push it toward olive, cool white lighting can make it look almost blue, so test an ornament under your own lights before committing to a whole box of the same tone.
When anything arrives, check the back and the underside before it goes anywhere near a tree or a mantel, that's where cheap glue joints and rough wire ends show up first. A decoration that's been well finished looks just as good from behind as it does facing out.
Even a plain room with bare walls and nothing else dressed up starts to feel like the season has actually arrived once the green comes out.