Growing Concerns 582: Renovate & redesign perennial beds

In this issue:

Perennial fall cuts
Perennial design
Caterpillar webs

Start cutting and rearranging perennial garden now for best spring show


What's the rule for cutting down perennials? Should it be done in the fall? In the spring? - C.G. -

Dear C.G.,

No one cuts perennials in their natural, non-garden habitats, unless you count browsing animals. So guidelines for cutting are gardener-oriented and subjective.

I start cutting perennials in June and continue through fall. I cut plants whenever they begin to look ragged. Right now my hit list features tall phlox, bee balm, globe thistle and daylilies. Those that fall after mid-July may produce new foliage later in that growing season or may go dormant for the year but either way, every one that was healthy and established before the cut will return in 2005. I'm as certain of their comeback as I am resigned to that of a big dandelion I decapitated in lieu of pulling.

Almost every perennial I grow receives this treatment. During the season I spare those with post-bloom foliage or seed pods I admire or use. So when my last toad lily and purple bush clover bloom in October, they do so in beautiful company, free of fading, disorderly neighbors.

At season end I pass over woody evergreens -- candytuft, sage, lavender, etc. -- and herbaceous species that can look good during winter. However, that rule is also made to be broken. In one garden I leave blackeyed Susan and feather reed grass to be enjoyed until the next April, but in another where no one will be around to see that duo in winter, I cut them in fall. In naturalized gardens, I never cut these two at all. Sometimes I cut them even though we'd appreciate their winter presence because one has leaf spot and the other has rust, infections that will be worse next year if that contagious debris is left in place.

When I cut, it's all the way to the ground. In some cases this means the plant is reduced to a clump of basal, semi-evergreen leaves. In other cases, the plant essentially disappears until spring..

Perennial question: How to design

When we purchased our house five years ago there were no perennials in the yard. Our yard backs up to 22 acres of woods, so I cleared six feet into the woods and planted some perennials. Now it looks very messy. I can't remember what everything is but there were Virginia bluebells, bleeding hearts, fern, Ligularias, leopard's bane and some wild woodland plants that have purple flowers in May.

To make it look better, do you plant all one type of plant together? What can I add? Are there any rules of thumb about tall plants in back or middle? I think my problem is there is no design to my work, everything is thrown in. - P.C. -


Dear P.C.,

When we design we start with about ten plants that will thrive on the site, fit the maintenance schedule, meet the goals for such things as cut flowers or attracting butterflies, and look good together even out of bloom. You're in a good place to try this approach, because now you know which plants can thrive there, which were enjoyable rather than taxing to maintain, and which pleased you most in other ways.

Start by making a list of "keeper" plants. List only those that pass all three tests -- will grow well there, are no trouble to maintain and are pleasing to you. Then note the shape, texture and foliage color of each plant. For instance, old fashioned bleeding heart is mounded, blue-green and medium texture. "Medium texture" means it's composed of segments that fail to blend into a solid "fine" mass when seen from a distance of about 20 feet, yet don't quite hold their own as distinct bits. In contrast, some Ligularias are coarse in texture by virtue of big, bold leaves with maroon undersides.

Look at your list for patterns, and add to strengthen a theme or build contrast. I think you will add plants that are mat-forming, vertical or vase-shaped, have foliage that is gold, white or variegated, and are either very fine or very coarse in texture. Goatsbeard (Aruncus dioicus), hostas such as 'Sum & Substance' or 'Sugar & Cream', white-edged Jacob's ladder (Polemonium 'Brise D'Anjou) and meadow rue (Thalictrum species) are all possibilities.

How many of each plant you need depends on the viewer. If the garden is seen most often from windows 60 feet away, you may need 12 white-edged Jacob's ladders to have an impact, but if the main viewer is just six feet away, two or three may be enough.

More on perennial design with illustrations, in Design a Perennial Bed.

Green thumbs up

to continuing the Master Gardener Program.

Green thumbs down 

to burning or cutting caterpillar webs from trees. The insects ate leaves but not wood or next year's buds. Your saw or flame will do more damage than they did!


First published 9/4/04