One of my most frequent calls among homeowners is to evaluate a sick birch. What I usually find is a stressed tree that has been over-pruned, over-fertilized, and growing in heavy turf. The tree is about 10-years-old with one of the stems completely browned out and a second showing signs of decline in the form of a couple of dying branches and fading color in the top of the crown.
White birch (Betula papyrifera) is perhaps one of the top five planted trees in Minnesota. People love them and they are in high demand. White birches are tremendously ornamental. They are splendid in winter when the milky white bark is framed against evergreens. Their yellow-gold fall color makes a vivid display.
What's killing these birches is drought, heat, and poor placement which predisposes birches to attack by the bronze birch borer (BBB). I often find them planted in retail parking lots, boulevards, and post construction soil which is the last place birches want to be.
The European birches (B. pendula, pubescens, platyphylla) are most susceptible to the insect, while the native birches (B. papyrifera, popuifolia, nigra) less so. River birch (B. nigra) is among the least susceptible. Paper birches like a cool, moist root run over their root system in prepared and amended soils with drip irrigation and organic mulch over the root zone, at least beneath the canopy. The chance of BBB infestation increases significantly because too few gardeners and landscape architects pay attention to those sustainability details.
Sadly, I find River Birch to be a poor substitute for White Birch and does not even come close to the latter's cultural attributes. I have found this tree to have substantial surface roots, which interfere with mowing, and are constantly dropping branches and twigs. They develop iron chlorosis on high pH soils and for this reason I would test the soil and make sure it reads pH 6.5 or below before planting River Birch.
And it's a big tree, capable of growing 70 feet high with a 60 foot spread. Often excessively pruned because they outgrow their planting space, drooping branches are lopped off to the point where no branches remain on the bottom half. They can look ridiculous. Pruning certainly leads to an earlier than usual death and the tree would do better if not pruned at all.
If you do want a birch, choose a native birch. Make sure of the scientific name, for any birch with white bark is a "white" birch. Plant them on the east and north side of a home where they get afternoon shade. If you can't give them the environment they need, there are plenty of artificial birches available.
The swooping, pendulous branches of river birch make it a poor choice for the residential yard. This tree is over-pruned creating vigorous water sprouts which require constant maintenance.
A paper birch (Betula papyrifera), that is dying as a result
of bronze birch borer attack.
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