If they did not have flowers, they would not be able to reproduce.
If trees didn’t have flowers there would be no seeds, and if there were no seeds, new trees wouldn’t come up each year. And if new trees didn’t come up each year, there wouldn’t be forests.
Every single tree in the world has flowers, though sometimes they are too small to be seen or are buried so deep in the leaves that nobody can find them. Certain trees have flowers that come before their leaves, so people don’t notice the tiny blooms, which usually are not very colorful.
Certain trees have flowers that have no petals, others are green and appear to be buds of coming leaves unless you look very closely. There are even trees whose flowers are too small to see without a microscope.
There is one thing you can always count on about a flower, and that is that there isn’t a tree alive that doesn’t have one.