Commentary: Nipping a birch problem in the bud
Q: Our 10-year-old birch tree has a smaller trunk coming out of the main clump. When would be the best time to remove it, and should it be sealed after the cut? — Paul Thulen, Breckenridge, Minn.
A: Removing the smaller fourth trunk from the clump birch is a good idea, as its position could severely squeeze the growth of the other three trunks and cause future trouble. It can be carefully pruned out now, removing it as flush as possible, without leaving a stump. It might take a bit of close surgery to saw it away without scraping the other trunks, but it looks possible.
First, cut off the trunk higher up to relieve the weight. Then make the finishing cut in the proper spot.
It's best not to treat the cut with anything. Trees have the ability to heal their cut surfaces, and pruning paints and sealers have been shown to have no benefit.
Midsummer is a good time to prune birches, as birches "bleed" less sap now. This from the University of Minnesota: "Birch pruning should not be done from May 1 to July 1. This is during the bronze birch borer flight period and it has been shown that female borers are attracted to fresh pruning wounds of birch. Wound dressings should not be used; they are ineffective at repelling borers and do not promote closing of wounds."
Q: My mom has built a new home in Hankinson, N.D. She had her lawn hydroseeded about a month ago. We had killed all the weeds with spray prior to it being seeded. The grass is coming in nicely, but so are lots of weeds. Is it safe to spray the new grass to kill the weeds? If so, what should we use? Or do we need to wait until next year to spray? — Sheryl Falk.
A: Weeds growing with newly seeded grass is normal. The weeds are usually annual-type weeds whose seeds are in the soil, ready to germinate right along with the grass seed, and are relatively easy to control. Your spraying prior to seeding should have removed the perennial weeds.
The best product to use in this situation is one that contains 2,4-D amine as an active ingredient. That will kill the "broadleaf" weeds, like dandelions, without harming the grass.
But it should not be sprayed on new lawns until the grass has been mowed three times. September is an excellent time to spray weeds. By spraying in the fall and again next spring, most of the weeds should disappear. The annual weeds won't live over winter anyway, so a percentage of them would die after killing frost. But it's best to spray because there are probably perennial weeds like dandelion whose seeds sprouted also.
Q: I have a hosta I need to move and another one I would like to divide. What would be the best time and method to do this? — Diane Rensvold.
A: The best time to dig, divide and/or move a hosta is in early spring, just as the new buds are barely breaking through the soil surface. Doing so at other times of the growing season increases risk, but it's sometimes successful if there's no other option.
In early spring, simply dig the hosta clump and divide with a sharp knife, allowing each division several of the swelling buds, and replant.