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While I do have a compost pile, I wondered if it is OK to use grass clippings and leaves as a mulch. I have heard that they actually remove nutrients from the soil as they decompose and, therefore, shouldn’t be used as a mulch. It seems to me that they would be actually returning nutrients to the soil as they decompose. Please advise.

Organic mulches such as grass clippings do eventually return nitrogen and other nutrients to the soil. However, during the early stages of decomposition, the microorganisms responsible for the breakdown of the mulch require nitrogen and will steal it from the soil. This may cause a temporary nitrogen shortage to surrounding plants unless it has been supplied with nitrogen supplements such as cottonseed meal, bloodmeal, or urea.

If grass clippings are spread too thickly, they will heat up and make a hot, slimy mess. If they are too close to the stems of young, tender plants, this reaction can cause damage. Further, as the layer compresses, it can become tight and allow only anaerobic decomposition, often producing a bad odor in the process.

While some gardeners may disagree, grass clippings are not a preferred mulch. It’s best to compost them completely in a compost pile and use the resulting rich humus to enrich new or existing planting beds.

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.

I have several globe-shaped yews that I trimmed around late June, after the first flush of growth. There was another flush of growth this fall that needs a little trimming to maintain the tight, globe shape. I have heard some say that nothing is supposed to be trimmed after August 15 and then others say a final, late fall/early winter pruning is OK.  Please advise.

As a general rule, heavy pruning should not be done after August 15. The reason for this is that trimming stimulates new growth which may not have sufficient time to harden off before the onset of frost and cold weather in the fall. Late fall or early winter pruning of evergreens is also not recommended since the open wounds created at the tip of each shoot will be likely to dry and cause further dieback which will require further trimming come spring.

In this case, one of two methods may apply. The first would be to selectively remove any feather growth (any which extends beyond the main body of the plant) with a pair of hand pruners. This will usually stimulate little, if any, growth. In the event that much more needs to be trimmed, the second approach would be best to use. Wait until early spring (around forsythia bloom time), then trim away as much as you would like. This means looking at a larger, more natural-looking plant through the winter, but since evergreens provide great winter color, the more the merrier! 

The deck in my back yard needs power washing, but it is surrounded by plants, mostly perennials and clematis. Can you suggest some cleaning solutions and/or methods to clean the treated lumber without harming the plants?

This is a difficult question to answer since new cleaning materials and methods come about every year. A good place to seek advice on which solutions are safe to use would be your County MSU Extension Agent (the phone number can be found in the phone book under the government section, county name, MSU Extension). Keep in mind that power washers can be damaging to plants just by the force of impact against the foliage so provide protection with canvas tarps or cardboard. If cleaning solutions are used, be sure to wash off foliage with your garden hose as early as possible and soak the surrounding soil as well to dilute any solutions that may enter the soil.

When planting clematis, I saw where someone cut the young plant back to just a couple inches in order to stimulate a thicker growth habit.  Is this recommended for our area?  Does it apply to all types of clematis?

When planting dormant clematis (either new or transplanted) it is beneficial to hard prune back to 6 to 12 inches to promote a fuller vine. If the plant is already growing, keep the plant intact for the first season so the leaves can nourish the root system and aid in establishment. You may then hard prune the following spring to promote the thicker growth.

Is it OK to put a nail or a screw into a tree to mount feeders, etc., or does this damage the tree? Is there a trunk diameter at which it becomes OK to do? Are there certain tree species that are particularly susceptible to damage?

An occasional nail or screw will not cause significant damage if carefully placed into wood that is greater than 6 inches in diameter. Remember that every wound creates the potential for decay, especially in weakened trees, so keep accessories to a minimum. These sites should also be checked annually to make sure that the outward growth of the tree is not restricted in any way. If needed, remove the nail or back out the screw to allow for this growth.

Certain tree varieties should be avoided if possible. These include birch, dogwood, cherry, plum and Japanese maple.

While planting perennials this fall, I scattered a few bulbs in each planting hole along with Bulb Booster fertilizer.  After backfilling the hole, I watered with a solution of Fertilome root stimulator, which I have used with great success for many years. Is this fertilizer combination a problem for either the bulbs or the perennial?

One should always be careful about overdoing a good thing. While I doubt you caused any harm in what you did using this combination, it would be easy to injure newly planted perennials by using too much fertilizer.

Bulb Booster is a slower-releasing fertilizer product that will provide root building nutrients over a period of weeks to the establishing plant. Fertilome Root Stimulator, on the other hand, provides immediate stimulation to the plant. It contains a root stimulating hormone to help initiate new roots, as well as a mild, water soluble fertilizer to aid in the plant’s establishment.

If the Bulb Booster is mixed with the planting soil, and both fertilizers are used according to package directions, I doubt that any harm would result from this combination. 

I want to move and replant many spring-flowering bulbs (daffodils, tulips, and alliums). It seems like a waste to throw them out because they are only 1 year old and looked great last spring. When is the best time to transplant? Any tips on digging the bulbs up without slicing through them?

Moving spring-flowering bulbs can be done anytime after the foliage has died down, following flowering in the spring. It is important to allow this to occur because the foliage is helping to rebuild the stored food reserves used during the flowering process.

Not all spring-flowering bulbs reflower dependably year after year. Many tulips, for example, do not have enough time to replenish themselves before the warmer weather moves in and dries the foliage. As a result, most tulips flower great the first year, not so great the second year, and often not at all the third.

Bulbs that flower earlier or are better able to withstand warmer temperatures are more likely to reflower year after year. Daffodils and alliums fall into this group.

If you move the bulbs when the foliage has dried, but before it detached from the bulb, you can more clearly see where the bulbs are located. Using a spading fork will make it less likely that you will slice the bulb, but there are no guarantees you will not stab an occasional bulb.