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.

A couple years ago when I created a walking path through my garden, I put down black plastic and covered it with wood chips. The chips are now breaking down and forming a compost that is spouting weeds and plants in the path.  If I remove the growth and replenish the wood chips, I’m afraid the same thing will keep happening. Grass is not an option due to the confined area.  Do you have any other suggestions for a natural path?

In our opinion, a plastic weed barrier should not be used under an organic mulch. This is especially true if a shredded wood mulch is used, as these mulches tend to break down fairly quickly.

This generally does not pose a problem when used as a mulch around trees and shrubs. In fact, the decomposition of the shredded bark aids in improving the soil. The mulch itself is an effective weed barrier if it is replenished regularly and maintained at a depth of 3 to 4 inches.

The plastic weed barriers are useful in preventing weeds under inorganic mulches such as pea gravel or crushed stone. Perhaps these could be considered for your pathway. Another option to consider would be decorative stepping stones.

The Clematis montana ‘Grandiflora’, I planted this spring is healthy, but one stem grew to 6 to 7 feet while a couple others at the base are only a foot long. To encourage denser growth, should I have been pinching it back throughout the summer? To get thicker growth next year what should I do now (if anything) and next spring?

Probably the most frequently asked question about clematis concerns pruning. Clematis are generally divided into three groups for pruning purposes. Your Clematis montana falls into Group A, which includes spring-flowering varieties whose flower buds were produced during the previous season. Therefore, any growth that is removed between late autumn and early spring will cause that much flower loss for the coming season. So, any pruning that you want to do to control the plant should be done in early summer. I wouldn’t be too concerned about encouraging dense growth, however, since Clematis montana is an extremely vigorous grower.

For your information, Group B varieties also bloom on the previous year’s growth. The recommended time to prune is February or March to remove weak and dead stems. The remaining stems are cut back to just above a pair of good green buds.

Finally, Group C consists of these Clematis that bloom only on new growth. Pruning these varieties involves cutting back all of the previous season’s growth to a pair of good buds usually about 10 to 12 inches above the ground. This should be done in February or March.

I have a 3 foot x 10 foot grassy area in hot sun all day.  I want to replace the grass with a low groundcover that can handle occasional, light foot traffic.  Due to the sun exposure, it would be nice if it were drought tolerant also. Can you suggest a few?

Before we mention the types of plants to be used, let’s first discuss the ground preparation. Since this planting will be subjected to heat and drought stress, as well as some compaction due to light foot traffic, the soil should be dug at least to a depth of a full spade (a minimum of 8 inches) and turned to break up any large clumps. Spread a 2 to 3 inch layer of sphagnum peat over the area and continue turning the soil until the peat is thoroughly mixed and the soil is fine and crumbly.

If foot traffic occurs in a few designated places, you might try placing decorative stepping stones there to absorb most of the compaction. You may allow the groundcover to grow around and over most of the stones if desired.

Groundcovers to select from include: bearberry, sedum (low types), thyme (several varieties), and yarrow (tomentosa).