- Use of any ash trees, due to the arrival of Emerald Ash Borer (EAB) in Wisconsin. (Ash trees (Fraxinus) are different from mountain ash (Sorbus). Sorbus (mountain ash) are not affected by Emerald Ash Borer
Other poor choices of trees include:
- Canadian Cherry trees: black finger fungus
- Autumn Blaze maple: poor choice in wind swept areas
- Newport Purple Plum: highly suceptible to coral fungus
- Austrian pines (Pinus nigra) in Dane County—Michael Dirr, whose encyclopedic book is an industry standard, warns against this practice
- Firs (Abies spp.) in Dane County. Firs do badly in Dane County's heavy clay soil. The exception is concolor firs (Abies concolor). Even these are iffy. They suffered mightily in winter of 2013
- Evergreens brought down from Christmas tree farms in northern Wisconsin sand country—their truncated roots can often fail to adjust to the in heavy clay soil of Dane County
- Black walnuts (Juglans nigra): secrete juglone, toxic to grass and many vegetables. The hull contains a brown/black dye that stains everything it contacts. The walnut seed hit by a lawn mower is a lethal projectile. This tree is best left in the forest.
- Too many small trees too close together, which grow into a malformed mess youthful and inexperienced landscape designers: minimum 10 year internship. They haven’t seen their plans into 10 year maturity there is little chance for the development of feng schwei.
- Some restrictive covenants require planting 3 conifers. The choice of white pines on a ¼ acre lot is ludicrous, as these trees can quickly become 40 to 50 feet in diameter!
- Designers that are captive to a single company: they prescribe what is surplus inventory, not what you need or put too many trees too close together because they are only authorized to use small plants.
- Insufficient conifer/ deciduous margins. Leaf trees shade out the conifers, leaving gaping holes in the conifer’s foliage, which becomes especially noticeable in the fall, as deciduous trees shed leaves
- Placing conifers too close together. The result is a bunch of Christmas trees on “telephone poles.” This is often done to make a green screen, but years later the exact opposite results.
- Conifers placed in an established deciduous landscape
- Colorado or Black Hills spruces in wet or heavy clay soil
- White bark birch trees in clay soils, especially where the root balls have southern exposure
- When planting potted trees beware of circling roots
