Is it normal for some of my 2x6 framing studs to have knots and green staining?

Those knots and green streaks are par for the course when you're working with standard **#2 grade** framing lumber. In the world of dimensional lumber, a #2 stamp means the board is structurally sound for framing even if it looks a bit rough. The grading agencies acutally account for those knots and holes when they set the strength ratings, so as long as a knot isn't spanning the entire width of the board or located right on the edge in a high-stress area, you're good to go. The green streaks you're seeing are ussually just a result of the pressure-treatment process or sometimes just a bit of kiln-drying residue and mineral streaks in the wood itself. If you bought pressure-treated lumber for an outdoor structure, that's definitly just the chemical preservative—usually copper-based—soaking into the grain. It’s not mold, and it won't rub off becasue it's literally cooked into the fibers. If it's just regular SPF (Spruce-Pine-Fir), it coud be mill marks or natural mineral deposits from the soil the tree grew in. When you're sorting trough your pile, the main thing to watch for isn't actually the knots, but the **crown** and the straightness. I usually set aside the "ugly" boards with the big knots and use them for blocking, fire stops, or shorter cripple studs where they aren't doing the heavy lifting. Save your cleanest, straightest 2x6s for your corners, headers, and any spot where you need to nail two boards togather perfectly flush.

Unless the board is literally snapping in half or has a knot so big it's created a massive structural void across the entire width, it’s going to hold up your structure just fine. Wood is a natural product, and the stuff you get at a lumber yard is never going to look like furniture-grade material. Just keep an eye out for "wane"—that's when the edge of the board is rounded off because it was cut from the outer part of the log—and excessive twisting. Other than that, you're likely fine. Get those studs up and keep moving.

If you're worried about those knots making the joints weak, just beef up your connections. I always use FastenMaster TimberLOK screws instead of standard nails for those 'ugly' boards. They pull the wood together tighter than any nail ever coud and you don't have to worry about pre-drilling. Even if a knot is in a weird spot, those screws bite deep and hold.

Plus, if you ever need to swap a board out later becasue you can't stand looking at it, it's way easier to back out a screw than pry out a bunch of 16d nails. Gives you a lot more confidence in the build.

I was totally freaking out about my 2x6s looking like this too! I'm a complete newbie and just started my first DIY shed. I was convinced my lumber was rotting becuase of those green marks, so this is a total relief. Since you mentioned using 'ugly' boards for blocking, I’m curious—do you guys think I shold buy a moisture meter? I saw a video of a guy using one to check his studs before drywalling and now I’m wondering if my wood is too wet to start building! Also, do I realy need a big miter saw for these cuts?

Quick update—knowing that these are just #2 grade makes me feel way better about those green streaks. I’ll definitely look into those TimberLOK screws to beef up the joints on the uglier boards. I’m still struggling with the pieces where the knots have fallen out completely, leaving big holes. If a hole is right at the end of a board, is it still safe to use for framing?