There are certain plants that are problematic even though they are used extensively in landscapes. Here is a short synopsis of the bad and some alternatives.
Boxwoods: Due to the boxwood blight, we can not recommend installing any type of boxwood including the Korean types. Any Japanese holly will substitute, especially, Soft Touch holly which can replace Dwarf English boxwood.
Leyland Cypress: The Leyland is very susceptible to several diseases. The worst of which is Seiridium Canker for which there is no effective treatment. Seiridium Canker takes advantage of minute cracks that have developed in the bark (often a result of dry conditions) killing branches and eventually the tree. Leylands also are susceptible to other stem canker diseases and some foliar blights. A good substitute for Leyland is Cryptomeria. Plant any of these trees on a 10′ plant spacing at a minimum.
Dwarf Indian Hawthorne: There are numerous varieties of dwarf hawthorne and all of them are susceptible to leaf spot to some extent. The University of Georgia has a great handout on the problems and the resistant varieties. In our experience, the Bay Breeze is one of the worst! Some of these varieties can also have trouble with temperatures in the teens. Stay away from the disease susceptible varieties and keep the others on a spray program and you may reduce the leaf spot issues. Using the cold hardy varieties is also recommended.
Otto Luyken Laurels (the laurel group): These plants have issues with poorly drained soils which leaves them susceptible to root and crown issues such as root rot and stem canker. They also are very susceptible to leaf spot, shot hole disease, scale and spider mites. The best replacement would be Japanese Compacta holly, a dwarf loropetalum such as “Daruma”, Dwarf Burford holly or Distylium. The Distylium is a member of the witch hazel family. They are evergreen, compact, disease and insect resistant, and are heat and drought tolerant. Distylium hybrids will also grow in damp soils. The plants require very little pruning. This plant easily replaces Otto Luken Laurels, boxwoods and hawthorns.
Knock Out Roses: These roses are highly susceptible to Rose Rosette Disease which is caused by a virus. Once infected, the roses begin to show severe growth aberrations such as witch brooming on stems and dwarfing. There is no cure or treatment. Do not plant anymore Knock Outs until a cure or remedy is developed.
Flowering Cherries: Yoshino and Kwansan have severe problems with Botryosphaeria canker for which there is no cure. Autumnallis and Okame are good alternative varieties.« Back to Glossary Index