stems fairly evenly spaced. Be sure to remove any weak or particularly thin stems
as well. If in doubt as to how many stems to remove, remove more shoots, or else
the thinning won’t be effective and the time spent will be wasted.
Thinning is a useful tool to help the perennial gardener create desired shapes
or appearances in the garden. I use thinning throughout the season if a plant has
become too full or dense for the effect I hope to accomplish, and again this may
mean thinning of flowers, leaves, or select branches and stems. When thinning in
the summer, flowers, leaves, and select branches usually should not be cut to the
ground—as entire stems should—but should stop at a lateral bud. An imbalance
of weight in a garden may not be obvious on casual observation, but too much
weight in the wrong spot will mar the overall appearance of the design. Scented
oxeye (Telekia speciosa), for example, has very large, coarse leaves, and if it isn’t
balanced properly with sufficient quantities of plants with finer-textured leaves, I
will thin some leaves and maybe some stems to lighten it up a bit. If I have used a
taller or slightly denser plant near the front of the perennial border to create a
more diverse cross section to the garden, I sometimes will need to thin its flowers
or foliage to allow a view through it to the other plants. A plant’s flowers may
seem to outweigh the poor stems that are trying to support them, and in such a
case, the plant itself is out of balance. Thin some of these flowers. Use them in the
home in floral arrangements and you will be happier all around. Purple-foliaged
plants add depth to garden designs, but too much depth can create a somber
feeling. Remedy this with thinning. Remember to step back and look at the plant
as you are thinning so that you see what you are creating.
Thinning can serve a variety of functions for a variety of plants. Delphinium,
Monarda, Phlox, and Symphyotrichum are a few genera that may be less prone to
mildew if their stems are thinned, although my experience has not shown much
of a difference in the mildew on thinned phlox as compared to unthinned.
Delphinium and phlox may also produce larger flowers if thinned by a third.
Other perennials such as bugleweed (Ajuga reptans), lady’s mantle (Alchemilla
mollis), Bethlehem sage (Pulmonaria saccharata), lamb’s ear (Stachys byzantina),
and some hardy geraniums often benefit from a summer thinning to improve air
circulation around the plant and prevent rot or mildew. I cut out some of the
dense foliage on Stachys byzantina ‘Helene von Stein’ to open it up a bit when the
humid weather comes, and this applies to other silver-foliaged plants as well.
With Alchemilla mollis, Geranium ×magnificum, and Pulmonaria plants, you can
pull out some stems while you are deadheading to thin the plants and reduce the
incidence of disease when water accumulates in the dense foliage. This can keep
plants from getting too large as well.DISBUDDING
Disbudding, the removal of flower buds, is a pruning technique that is usually
associated with growing plants such as mums, carnations and pinks, dahlias,
and peonies for floral shows or arranging. When disbudding for shows, side buds
are removed so that the plant’s terminal bud will produce a larger flower on a
longer stem. Disbudding at least 2 pairs of the side buds is best; for even larger
blooms, remove 3 pairs. Removing the terminal bud will cause the side buds to
produce smaller but more numerous flowers. Disbudding the terminal bud can
also eliminate the need for staking in the garden. Removing side buds along the
spikes of perennials such as lobelia or delphinium is not effective, but you can
remove smaller side spikes from these plants and other spike-blooming plants
such as aconitum for a larger terminal spike. Whatever the method or intention
of disbudding, buds should be removed before they get too large, otherwise
unsightly scars will appear.126 PruninG Perennials