Two weeks ago I noticed a that the skinny sweet birch sapling in the meadow looked wilted all over. We've had plenty of rain, but I watered it and waited.
A week later it looked even wiltier and most leaves had browned.
I tried again with three new saplings in 2013. One died the first year, and of the two surviving, this one out in the open meadow is now looking bad.
I thought it might have verticillium wilt, a fungus that infects the sapwood and prevents water transport in the trunk. Leaves show marked droopiness, then brown, and then the tree dies.
It's common in many hardwood trees. Diagnosis is confirmed when you cut open the trunk and see telltale brown rings.
The trunk of my little sweet birch is only the width of a pencil, and the branches are even smaller. I didn't want to sacrifice the whole sapling by cutting open the stem, so I just snipped off a couple thin twigs to see if any brown rings were evident.
It was hard to tell on such small branches, but they looked clear. There was no evidence inside the slender twigs of any discoloration.
The problem may not show up in the side branches, though -- it may be limited to the trunk, but if the trunk can't carry water the upper branches die. You can cut a scar on the side of the trunk to see any damage without having to saw it in half, but there just isn't enough size to this thing to slice open the side of the trunk to see anything.
So should I cut down the sapling? Verticillium wilt is fatal. The fungus persists for a long time in the soil, so you can't replant the area with any other tree that is susceptible; the new planting will soon be infected.
My tree isn't completely dead yet, so I'll wait. But if I have to take it down, it will be an easy bit of work. One snip with the pruners will do it, and I can then see if verticillium wilt is showing in the trunk.
I guess I'm done trying to grow Betula lenta. One lone twiggy sapling survives, but my track record getting sweet birch saplings to grow is poor.
I really liked it as an addition in the woods-becoming-forest behind our house. It's native, it has a nice form and rich yellow fall color. The bark is shiny and interesting, and when scratched it smells and tastes of wintergreen. How I wish I could grow a sweet birch here.