Since spring tree planting season is around the corner, I've copied below a response to a recent inquiry about planting larch. The question was why not plow up the field before planting to get rid of the weeds?
Plowing (besides the considerable cost) will disturb the soil and create an ideal seed bed for tall weeds, multiflora rose and all sorts of other undesirable plants to quickly occupy the site. Unless you have an opposition to herbicides, I would recommend using a systemic herbicide like glyphosate (active ingredient in round up) to kill the sod in strips prior to planting. Even though there will be a little bit of soil disturbance and weed growth during the planting, it’ll be much less than with plowing. The dead sod acts as a temporary mulch to keep moisture in and weeds out. You’ll also avoid having to pick lots of stones after plowing which would be a hazard if you plan to mow the young plantation for the first few years (recommendable) – otherwise, the bunnies and mice will raise havoc with the seedlings!
The ideal site prep. and maintenance scenario would be to strip spray in the fall, plant in the spring, mow once or twice a year for the first few years, and possibly (very carefully) spray around the young seedlings for the first 1 or 2 years after planting – preferably either just before the buds start to swell on the larch in late April, or towards early October when the grass is still green but the needles are for the most part falling from the young larch. If larch isn’t actively growing it can tolerate very minimal spray drift (careful spring or fall spot spraying around base of trees). Reduced root competition from herbaceous plants is the most important management consideration and will make a huge difference in survival and initial growth of the young trees.
Site preparation and follow-up are expensive . I planted about 8000 Norway spruce without site prep and no follow-up in an old pasture about 1985 under the supervision of forester A in about 1985. I was told at the time that the lplanting conditions were nearly perfect. By 1995 there were only about 20 still there.
In about 1995 I planted about 5000 spruce and 5000 larch in the same field without site prep or follow-up under the supervision of forester B. Most of the larch are there and growing well today. Many of the spruce have suffered from the white pine weevil.
What can we learn from this? Not sure.