I want to plant a low hedge of boxwood, roughly 2 feet tall, to serve as a border around an English-style perennial garden. In the last couple years, I have seen boxwoods with some bad winter burn. Can you recommend a few varieties that are low-growing and hardy to Michigan winters?

Many boxwoods have suffered through our recent winters. Unfortunately, even the most hardy boxwood varieties may have difficulties surviving our Michigan winters unless they receive the proper soil conditions and protection from winter sun and wind.

For starters, boxwood should be planted in a very well-drained, slightly acidic soil (pH 5.5 – 6.5). Heavier soils should be thoroughly worked to incorporate amendments such as sphagnum peat and pine bark. Prepare an area at least twice the diameter of the eventual plant size and for the length of the hedge. Mulching the soil surface is also important to keep roots cool and evenly moist, while providing protection from winter cold.

Choosing the proper location for planting boxwood is also important. Ideally, they should receive no direct winter winds and little direct sun from the south and west. This means eastern exposures provide the best protection from damaging elements. Other microclimates such as courtyards, evergreen screens and wooded areas may also work as long as they provide this same type of protection.

For varieties that stand up better to Michigan winters, try Korean Littleleaf, Winter Gem or hybrids such as Green Gem and Green Velvet.

I have a large, globe-shaped yew (about 7 feet tall) that looks great – the foliage is dense on the outside and its needles are a healthy, dark green. However, when I peer inside, the branches are all bare and the only green growth is on the last 5 or 6 inches of the branches. Is this normal?

Many evergreens, including yews (taxus species), junipers, and arborvitae have a “dead zone” or hollow spot in their interior. There are several causes for this lack of foliage on the interior of the plant. First, as evergreens grow, their new growth is mainly on the exterior of the plant. As the exterior of the plant thrives, the center of the plant receives less and less sunlight. The interior branches are shaded out and die off.

A second cause for the “dead zone” is the natural needle shedding of evergreens in the fall. Evergreens lose their oldest needles, those in the center of the plant, in the fall as a protection from having to support too much foliage over the winter. This shedding of older needles is especially apparent on white pine (Pinus strobus) and arborvitae in the late fall.

I assume its OK to keep fertilizing annuals in September to help keep them blooming as long as possible, but what about perennials – are there any perennials that should be fertilized at this time of the year (to help overwintering, next year’s blooms, etc)? 

The timing of fertilizer applications on herbaceous perennials is indeed important. Problems arise when nitrogen fertilizers, applied late in the growing season, stimulate new growth when plants naturally want to go dormant. With all but a few exceptions, most perennials do quite well with a light annual application of a balanced granular fertilizer in the spring. Perennials that are either heavy feeders, such as delphiniums, or those that are in bloom for a long period of time, may require additional fertilizer in the middle of their growing season. A little experience will help you recognize when a particular plant has that “hungry” look. This simple fertilizer regime will assure you that your plants are going into winter dormancy in good condition.