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I planted a butterfly bush late last summer and it did very well. Early this summer new foliage appeared at the base but no new growth occurred on the branches. Am I supposed to cut the dead branches back to the ground or leave them alone?

One of the greatest treasures for providing life in the garden is the butterfly bush. Hummingbirds and beneficial insects, as well as butterflies, are seduced by the nectar-rich flowers of these bushes. Most plants offered are of the species Buddleia davidii. These large, hardy shrubs (even the dwarf shrubs can reach 8 to 15 feet) are highly ornamental, extremely carefree and very vigorous growers. Buddleias remain evergreen in winters where the temperature does not drop below 20 degrees. Where winters are more severe they can be deciduous, merely dropping leaves, or herbaceous, freezing completely back to ground level. Phenomenal growth is achieved in one season even if they do freeze all the way to the ground. The normal life cycle of this bush is to go dormant in zones 5 and 6. At this point the canes above ground are dead. In early spring, after any danger of hard frosts, they can then be pruned to the ground or you can shorten the main stems to a low framework of 6 to 18 inches. If you are in a marginal zone 5 area, it is a good idea to apply a 3- to 6-inch layer of mulch covering the crown. Since it self-seeds prolifically, it’s best to remove spent flower heads promptly. This results in a second flush of flowers in late summer. No landscape should be without at least one butterfly bush!

I am trying to hide my air conditioner unit. What plants can I place around the unit that will not harm it, nor the unit harm the plants?

That all depends on the air conditioner’s location. If there were a large planting area, you would be better served to distract the eye from the unit with a mixed planting of woody ornamentals and tall grasses, as opposed to drawing attention to it with the ubiquitous soldier course of evergreen shrubs. Always allow a constant 3- to 4-foot minimum clearance around the unit for the inevitable maintenance and for proper airflow. Now, if extra space is at a minimum, such as your condenser being adjacent to the patio, it would be better to have a screen, such as vented fence sections surrounding the visible sides. Dry-set the posts so the sections can be removed for servicing. If done well, it would add an attractive privacy screen effect as opposed to a cover-up.

Is it okay to add old, stale bread to the compost pile? What about tree stumps – can they be buried in the pile to speed their decay?

No, bread should not be added to a compost pile. As far as tree stumps, I wouldn’t add them to the compost pile. They will eventually decay in a long, long time, but in the meantime you will upset the balance in your pile and you won’t be able to turn it to speed the decomposing process. A balanced pile needs both green and brown materials. I would chop it up and use it for a nice bonfire, or maybe rent or borrow a chipper and use the chips around your garden, with maybe a small portion of the chips added to the pile.

This spring I had grass sprout up all over my garden beds. Last fall I put down a 1-inch top dressing of my own compost, which was about a year old at the time. I have been doing this for several years and never had any grass grow in the beds. Is it from my compost or something else? Are there any reasonable methods to prevent it from happening again?

It is most likely not from your compost. Grasses propagate through the growth of tillers and rhizomes. The tillers look like blades of grass that grow along the surface and send down roots where they contact bare soil. In working your garden, you are taking the tillers out in your normal cultivation. Rhizomes grow laterally from the grass, underground. They then send up shoots at points along their length. Often, if you were to pull up a three- to five-inch tall shoot, you may find two feet or more of root. This root is the rhizome. Over time, rhizomes will work their way under or through most bed edging. Pulling up the shoot and as much of the root as possible is the best way to fight back. Using the types of chemicals that would be needed to kill back the grass could harm other plants in the bed, so a chemical solution would not be a good choice.

I’m wondering when is the best time to prune my Oregon grapeholly? It is a standard-size Mahonia, not a compact variety. It’s so pretty in bloom, but it needs trimming – if I do it now I’ll lose all the berries. If I trim it in the fall, will I lose the spring blooms? I hesitate to prune in fall because of the browning that occurs over the winter, which already takes a fair amount of leaves. Please help!

Sometimes in gardening, as in life, we find ourselves between a rock and a hard place. So it is in deciding when to prune your Oregon grapeholly (Mahonia aquifolium). As you’ve discovered, cut back this evergreen ornamental shrub in early spring and the slightly-fragrant, pyramidal-shaped cluster of bright yellow flowers won’t emerge during their typical April to May blooming time. Prune this shrub in early summer and there won’t be any of the bird-attracting, grape-bunched, chick pea-sized, blue-black berries in late July.

You must, however, prune to keep this vigorous-growing ornamental (it can reach nine feet) looking tidy. If you’re willing to sacrifice the flowers or the berries for a season, you can hard prune any time of the year, except early autumn. If you prune in September or later, the new growth that will be stimulated may not harden off before the killing winter cold. On the other hand, light pruning (cutting back one stem in three) in early summer will preserve most of the flowers and/or berries.

In terms of cultivation, if many of the lustrous green, leathery leaves die during the winter, perhaps your Oregon grapeholly needs to be moved to a different site. Hardy to zone 4, this native of the Pacific Northwest likes moist, well-drained, acid soil in a protected location; it doesn’t like exposure to excessive heat, dry soil, and desiccating winds.

How you can tell a male kiwi plant from a female kiwi plant?

Kiwi plants are dioecious, meaning that male flowers occur on one plant, and female flowers on another plant. One sure fire way to know which you have is to observe which plant bears fruit; that most certainly will be the female plant.

However, not having fruit does not guarantee that you have a male plant, as many factors can prevent fruit from forming on a female kiwi in our Michigan climate. The truly scientific method of determining male or female is to use a hand lens to inspect the flowers. A male plant will have flowers that have no stigmas, or have undeveloped stigmas. A female plant will have flowers with ovaries that are prominent and with stigmas, but without stamens. If you do not have a diagram of flower parts and actual flowers to inspect, the best approach with a kiwi is to purchase your plants from a nursery that has identified the particular plant as male or female. Be sure to grow at least 1 male plant for each 8 female plants in close proximity to ensure fruiting.

If you have the opportunity to visit the 4H Children’s Garden in East Lansing on the campus of Michigan State University, be sure to see the large and vigorous hardy kiwi on a large, sturdy trellis in the amphitheater garden area. Sorry, I don’t know whether it is male or female, so take a hand lens with you if you visit while it is blooming this spring. For a virtual tour of the 4H Children’s Garden on the Internet go to http://4hgarden.msu.edu.

I heard someone say they made a 50/50 blend of soilless potting mix and regular garden soil for a container planting. Why would this be done and for what types of plants?

A 50/50 blend of soilless potting mix and regular garden soil is fine as long as you can control the amount of water the container will get. Garden soil will retain moisture for longer period of time which can be helpful with smaller containers or hard-to-water areas.

The negative is that we cannot control the weather, so during the summer when we might get a few rainy days in a row, you could easily end up with root rot.

A straight soilless mix does dry out faster, therefore more frequent watering is needed, but you have a far less chance of overwatering and your plants will root out much faster.

I’m thinking about growing dahlias this season. What are their cultural requirements (soil, sun, etc.) and how do I overwinter them?

Dahlias are not only beautiful, but they are also extremely easy to grow. They require at least 6 hours of direct sun a day and enjoy a well-drained, light soil mix. Dahlias can also be grown successfully in large containers for your porch or deck. Like any large-flowered annual, deadheading is important throughout the season, as well as fertilizing every third watering with a water soluble 20-20-20 fertilizer to keep your dahlias blooming all summer.

When the first light frost kills off the top growth, simply dig up the tubers, remove all foliage and stems, wash off any excess soil, and allow to dry on newspaper for a few days. It’s a good idea to dust with Bonide bulb dust to help keep them free from disease. Cover the tubers with dry sphagnum peat in a paper bag or box and store in the basement for the winter. For best results, the bulbs should maintain a 50 degree temperature at all times.

Are tomato plants supposed to be pruned?

A light pruning can be done on tomatoes to help yield more fruit and extend the growing season. Understand though that pruning is not just cutting away at the plant anywhere! Only prune the suckers away from where the main stem and the branches meet.

The disadvantage of pruning is the lack of foliage to help shade the fruit which protects them from sun scald.

To achieve the early fruit and keep enough foliage for shading, prune suckers from the lower 14 to 18 inches of the plant and let the rest of the tomato bush out and produce a bountiful harvest.