Got a fifty foot tree with some grass around it that I'm trying to get rid of, will round up kill the tree if I use it to get rid of the grass?

nope.

In some cases it won't even kill the plant it's intended for. Just kidding, but I'm not a big fan of Roundup because it's too expensive and I seem to have as good or better results with some of the cheaper products.

What's a good non selective weed/grass killer then?

I like the Spectracide product which runs about half the cost of RoundUp (even less if you factor in coverage area), and is rain resistant like RoundUp. Plus I see results in about 3 hrs instead of a couple of days and it keeps my gravel area clean longer, so less repeat spraying required.

I also stock up at the end of the season when Lowe's has it on clearance so I save even more.

Harvey Updyke recommends Spike 80DF...

[This message has been edited by GetThoseKeysMilo (edited 3/25/2011 8:28p).]

Round up will not kill a large tree. Round up by far is one of the best weed killers there are. You just have to know how to use it. Moderation is key!!! Do not drench the intended target with the formula, simply hit the target with a single spray and in a few days the plant will be dead and should not come back. When you completely saturate the plant in round up, it will turn brown simply because the chemical burned the leaf. With a light dose, the plant actually takes the chemical in and the root and all all killed. Believe me, a teaspoon of round up in a gallon of water is hot enough to kill just about any weed.

Roundup is absorbed through the leaves of the plant...or the blades of grass. The leaves uptake the chemical that then inhibits protein production and kills the weed/plant. It is not taken-up by the root system, though it will eventually get to the root system as it travels through the xylem and phloem.

So, around the base of a tree, you could douse the grass/weeds and it will have ZERO adverse impact on the tree. You could pour 5 gallons of roundup on a tree trunk or exposed roots and nothing would happen. The only way it might affect a tree is if you doused the entire canopy of the tree continuously with lots or roundup. Even if you get a little drift while spraying the ground, you will be just fine.

So, spray away.