What mower/trimmer/other would you guys use to maintain the grass and weeds in a large field of Balsam firs planted six feet apart? I have used lawn a lawn mower, but some years we get behind and the grass and weeds get over three feet tall before we can get to them. We have tried Round-Up, but that leaves nothing in place to prevent erosion, nevermind not being able to drive anything near them after it has rained. All ideas are welcome. Thanks.