When do I prune my hydrangeas?

When to prune depends on the type of hydrangeas you have. Pink and blue hydrangeas (Hydrangea macrophylla) and oakleaf hydrangea (Hydrangea quercifolia) bloom on last year’s wood. They should only be pruned just after flowering. Pruning them in late summer, fall or in spring before they bloom will remove the flower buds for next year’s blooms. PeeGee, Annabelle, and tardiva hydrangeas (Hydrangea paniculata and H. arborescens) bloom on the current season’s growth and can be pruned in fall, winter or early spring.

Five years ago I planted a large trumpet vine (‘Madame Galen’). It has grown into a beautiful shrub, but has never flowered. It gets full sun, is protected by and planted on the south side of our shed. I have tried different fertilizers, raised the pH, lowered the pH, pruned it, and not pruned it. A few neighbors have trumpet vines; they put little effort into them, yet they flower.

Getting a trumpet vine to flower is simiar to getting a wisteria to flower; it sometimes takes patience. First, make sure the location you choose has lots of sun. Plants in shade rarely flower. Second, avoid high nitrogen fertilizers. If you have a lawn service, don’t let them fertilize near the trumpet vine. Nitrogen fertilizers promote vigorous stem and leaf growth which will take away the plant’s energy from producing flowers. Third, prune the plant back each spring to only a few buds per stem. This way the plant is expending less energy on vegetative growth (stems and leaves).

If these methods fail to produce flowers, you can try fertilizing with a high phosphate fertilizer such as superphosphate or try root pruning. Root pruning is cutting a circular slit in the ground that is centered around the stem of the plant. The circle should be 2 feet in diameter for every 1 inch of trunk stem diameter. Use a sharp, pointed shovel to make the slit by digging into the ground as deep as possible and rocking the handle back and forth to create a V-shaped cut. You can apply the superphosphate directly to this cut if you like. Root pruning often produces flowers the following year. Once the plant begins to flower, removing the seed pods will encourage more flowers.

Can you recommend some annuals for partial sun that have nice flowers and a spreading habit that covers a relatively large area? Rather than plant a traditional groundcover, I would like to try annuals, since they have season-long blooms and I can change them each year.

There’s a good reason that impatiens are the number one variety of annuals grown today. Not only do they bloom all summer long, but they spread together which reduces the need to weed. Impatiens are very low maintenance and will grow in sun, part sun or shade. Wax begonias will also bloom all summer and grow in part sun but won’t spread quite as much as impatiens. The colorful leaves and spreading habit of coleus would add an interesting look to a flower bed. Coleus will also grow well in part sun or shade.

I bought an iris that I understood was a repeat bloomer. Unfortunately, there wasn’t a second set of blooms. Are there indeed iris that do have another bloom in late summer or fall? Are either the bearded or beardless types better for repeat blooming?

The iris is a wonderful and beautiful plant that graces many perennial borders. The bold, exquisite colors of the flowers and the magnificent texture of the foliage make the iris a staple in many gardens. The early-blooming varieties are some of the first splashes of color seen in spring and are much appreciated after a long, Michigan winter! Adding a repeat-blooming variety to your garden gives you a fresh taste of spring as it blooms in May and, when it blooms in the fall, also serves as a reminder that it will be back to delight you next season. The most common repeat-bloomers are indeed the German bearded varieties. “Enchanted One” and “Immortality” are two varieties that will rebloom in the fall. “Autumn Sunset” and “Kansas Inglesides” are potential rebloomers, although not as reliable as the two aforementioned varieties. Some dwarf irises will rebloom in the fall as well. “Eleanor Roosevelt,” “Sangreal” and “White Autumn King” are three wonderful selections.

I haven’t tried planting containers because I am not able to water them regularly. This summer, however, I would like to try a couple. Can you suggest some groupings of annuals that look good together and like to be on the dry side?

There are several varieties that can thrive in drought conditions. Try a few simple things to help insure success. Try to use large containers over 14 inches wide. More soil in the pot means a longer time between waterings. You can also add water-retaining crystals to your soil, which will help retain moisture and release it as needed (Soil Moist is one brand). Here is a list of annuals that are not only drought tolerant, but are compatible also: wax begonia (upright), Portulaca (trailing), blue Victoria salvia (upright), vinca vine (trailing), spike (upright), Dianthus (upright), English ivy (trailing), Nierembergia (trailing), Gomphrena (upright), Gazania (upright).

I am looking to add fragrance to my garden this season. What easy-care plants do you recommend? Are annuals or perennials better suited for this task?

You can use both annuals and perennials to add fragrance to your garden. Perennials will return year after year and annuals will give you that “all-summer” color. Here is a list of some low maintenance, fragrant flowers:

Annuals: Nicotiana sylvestris, heliotrope, scented geranium, Alyssum

Perennials: Baby’s breath, butterfly bush, Dianthus, lavender, hybrid lily, peony, most herbs

I have several rhododendrons in dappled shade that bloom pretty well and are relatively healthy. Each year, however, leaves near the base of the plant turn yellow and drop off. Is this typical or is it a problem I should correct?

What you may be experiencing is normal leaf drop that occurs on all broadleaf evergreens in late fall or early spring. Even though these plants keep their leaves all winter they still go through a natural process each fall where older leaves are shed. Some of these leaves may remain until spring when they finally drop off. If you are experiencing leaf drop at other times, such as mid-summer, this may suggest a cultural problem. Insufficient moisture in dry summers may cause some leaves to drop.