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Although many people are not aware of this, one of the best things
you can do to keep your perennial garden looking well groomed all summer
is to prune the plants regularly. This has been especially important
this year when many plants grew up to twice their normal size due to
all of the rain we had this spring.
Pruning can mean anything from deadheading, which is removing the spent
flower heads, to cutting plants all the way down to the ground. Pruning
can do many things including, extending the bloom period or promoting
rebloom, encouraging lush new growth, reducing plant height, keeping
plants in their own space and staggering plant heights and bloom times.
I think the single most important type of pruning we can do is to deadhead
spent flowers. This often extends the bloom period of the plant by encouraging
growth of additional flower buds. How far below the spent flower you
prune depends upon the growth habit of the plant. Look on the stem below
the spent flower and see if there are any new flower buds forming. If
there are, prune to just above the first flower bud below the dead flower.
This works well for Rudbeckia (Black-eyed Susan), Lucanthemum (Shasta
Daisy), Echinacea (Purple Coneflower) and Monarda (Bee Balm). When you
see no more flower buds on a stem on these plants, cut the stem to the
ground. This will promote lush new growth at the base of the plant.
Although you will probably have no additional flowers for the season,
you will have attractive foliage. One more word about Black-eyed Susans
and Purple Coneflowers -- their seed heads attract birds. If you are
interested in feeding the birds, leave some of the spent flowers on
the plant at the end of the bloom period. Be aware though that in addition
to providing food for the birds, the plants will reseed themselves in
your garden if the seed heads fully develop.
Many perennials, like geraniums (not the annual Pelargonium that we
call geraniums), and Thread-leaf Coreopsis have fine foliage and small
flowers. Rather than removing individual flowers, these plants can be
deadheaded by shearing off the tops after the first bloom. You can actually
remove the foliage of these plants to within 4 to 6 inches of the ground
if you want to. This shearing helps keep the plants in their place and
promotes rebloom.
Daylilies (Hemerocallis) are another perennial that can begin to look
straggly in mid summer. Daylilies produce only one cluster of flowers
on a stem. You should remove the entire stem once the flowers have finished.
On repeat-blooming daylilies like 'Stella d'Oro' this will encourage
rebloom. On daylilies that bloom only once, removing spent flower stems
simply improves the appearance of the plant. If the foliage of a daylily
begins to look really bad, you can cut it of to within 2 or three inches
of the ground after bloom. This will promote lush new growth.
Some perennials just get too tall for their space, or so tall that
they tend to fall over. You can reduce the size of these plants by cutting
them back once or twice before they bloom. Although this will delay
bloom slightly, you will generally have shorter plants and more flowers.
This technique works well for Bee balm, (Yarrow) Purple Coneflower,
and Lobelia cardinalis, among others. The technique is to cut the stems
back 3 to 6 inches when flower buds begin to form.
You are probably beginning to get the idea that I think pruning perennials
is very important. I want to mention one more type before I close. Some
perennials are planted in our gardens specifically for fall color, like
Chrysanthemums and Asters. However, these plants will bloom in mid summer
if they are not cut back once or twice in early summer. Generally the
plants should be cut back by about one-half to two-thirds when they
are 12 to 16 inches tall. Not only will this delay bloom, it will produce
more compact plants with more flowers
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