These are different grades of Hickory flooring. The only way to minimize the variation in the floor is to stain it the darker color.

You can't get the dark pieces lighter.

Less expensive flooring often comes with a huge variation in boards. My guess is this is what happened here.

You cannot lighten the dark boards, but you can add dark stain to the whole floor that will make the lighter boards the same dark color. Maybe someone here with better skills than mine can make a rendering of what a whole floor in your darker colored boards would look like.

I think you will have to do a lot of color testing to figure out what the end result will look like. Do you have overage to test on?

Thank you for your comments, Beverly and Kendrah. Do you have any suggested stains?

Hickory is very difficult to stain, so it probably should be done by a professional (otheriwse it will be blotchy). If you give your floors some time, the dark boards will fade and blend in better with the lighter boards, leaving some dark-character marks. That's what happened to my un-stained hickory floors.

Thank you, Theresa. Yes, we are using a professional, but have not found a stain that covers well. I do like the floors, but the variation is much more than we anticipated.

Carrie, like you, I have a rustic hickory flooring with lots of character knots. It was a choice to choose character-grade hickory rather than a higher-grade clear hickory with select boards that Beverly showed.

Unlike some other kinds of hardwoods--such as cherry, which darkens with time--hickory fades a lot! I do not know how much your dark boards will fade if the stain is blocking some of the UV-light. I would talk with a professional. A lot of people on this site just don't understand hickory.

I had darker oak stairs that I wanted to match with my pre-finished floors. I was told I needed to bleach the stairs first and then stain them. However, I had heard about a stain expert at a paint store nearby so I brought him various samples of the new floor and a piece of darker oak that was about the color of my stairs. He mixed a thick matching stain that looked like latex paint. It was wood color, not white.

The paint-like stain flipped out my floor guy when I brought it to him to try but with some coaching from the stain guru he put it on. It's like a white wash process with color. Paint it on and wipe it off. Let it dry and put another coat until the wood is lightened up without losing the grain. It absolutely lightened the dark wood to a range where it was not so jarring with the new floor, without adding a pickled finish. No bleaching necessary.

This type of stain could help you tone down the contrast at least.

This is a problem created by choosing the wrong material. It's impossible that you are discovering this grade of hickory at this stage. Select & Better, #1 Common, Character, #2 Common and #3 Common are the different grades. Select and better may have allowed you to get the look you want. With what you have now, removing the wood and starting over is the path to an acceptable outcome. Even bleaching or cerising won't overcome the stark tone differences.

herbflavor, thank you for your thoughtful comments with pictures. Very helpful!

Call Hurst. They are suppliers of all grades and widths of unfinished hickory flooring. Unfinished Solid 5" Hickory Hardwood Flooring at Cheap Prices by Hurst Hardwoods | Hurst Hardwoods They can discuss a range of options at different price points. You can live with this or accept an error and reset to move forward for a long future.