University of Maryland: Garden Q&A
Q: I was told I must use something called mycorrhizae when I plant my trees. What is it and is it necessary?
A: The ability of mycorrhizal fungi to extend the root system of plants to an astounding degree is undisputed. These microscopic fungi are essential to most plants. Mycorrhizal fungi form a symbiotic relationship both inside and outside roots which helps to increase the root network for better access to water and nutrients.
In healthy soil, mycorrhizal fungi are already present. There are many species of these fungi and different plants require different micorrhizae. The question is whether commercial products deliver the same results as mycorrhizae in its natural environment.
Homeowners may derive the most benefit from commercial products when planting in soils which have been rendered lifeless during earth-moving and construction or whose microorganisms have been killed by heavy fertilizer and pesticide use.
However, organic amendments, such as compost, teem with microorganisms including mycorrhizae and can be incorporated into your soil to renew lifeless soils.
Q: Our house sits close to the road and I would love to put in an evergreen hedge and fence around it. Yaupon Holly hedges look beautiful in Williamsburg. I want to sheer it to a formal look, as our home is an old style. Will that work?
A: Yaupon holly (Ilex vomitoria) is not reliably hardy in Maryland. Being near the road would stress it further with road salt and pollution. Japanese holly and yews are both listed as being more salt tolerant, and they can be sheared and maintained as a formal hedge.