whether this type of pruning is needed. I have some old Salvia ×sylvestris ‘East
Friesland’ plants that in most years do not produce many new flowers from
lateral buds. Instead, after the initial bloom they open up in the center, begging
to be cut back to new basal foliage, which in turn gives me some rebloom.
Younger plants of the same cultivar produce nice lateral flowers, with deadhead-
ing, before needing to be cut down. Observing the plants and using a little
common sense are usually your best guides to what type of cut is in order.CUTTING BACK FOR HEIGHT CONTROL AND TO
STAGGER OR DELAY BLOOM—PRUNE BEFORE
FLOWERING
For many summer- and autumn-flowering perennials, cutting back before
flowering can help limit the plant’s height. Especially in areas of high winds,
controlling mature height may be needed to prevent plants from flopping or to
eliminate the need for staking. This approach to pruning can also be used to layer
a planting by creating interesting gradations in heights. Furthermore, overly
fertile soil and too much shade for a sun-loving plant will produce leggy growth,
and cutting back before flowering will often produce plants with a nicer, fuller
habit as a result of increased branching. Many times, depending on the species,
cutting back before flowering will produce smaller but more numerous flowers.
When perennials are first planted they often benefit from cutting back for fuller
first-year plants.
Bloom time in the garden can be staggered by selective pruning, and this can
be used to the gardener’s advantage in several ways. Simply pruning separate
plants of the same species a week or so apart, or pruning only part of a group and
leaving the rest unpruned, will stagger flowering by delaying bloom in the
pruned individuals. Individual plants can also be pruned so that their flowering
will coordinate better with a later blooming species. Staggering or delaying
bloom extends the season of interest in a garden, particularly in a mass planting,
and the technique is often used by public gardens for this purpose. Of particular
note is Stonecrop Gardens in Cold Spring, New York, where different “moments”
are created in the garden by pruning certain plants for special flower or color
effects at specific times. I too have employed this technique when I have putAmsonia plants benefit from
shearing back by a third and
shaping after flowering, here
showing Amsonia elliptica. The
plant on the left was sheared by
a third and shaped after
flowering; the plant on the right
was not pruned and has a
tendency to open up.
112 PruninG Perennials