University of Vermont Extension
Department of Plant and Soil Science
Summer News
Article
PRUNING LILACS AND OTHER JUNE
GARDENING TIPS
Charlie Nardozzi,
Horticulturist and
Leonard Perry, UVM Extension
Horticulturist
Pruning lilacs, controlling iris
borers, and proper weed whacking are some of the gardening activities
for this
month.
After
lilacs finish flowering, you can “deadhead” or prune off
the old
blossoms. To
reduce the height of the shrub, prune the old stems to the ground and
allow new
suckers to grow and flower. If plants
are large, taking one-third of the old stems out over a three-year
period
doesn’t create the dramatic butchered effect of pruning all at
once.
Some prefer to prune in late winter when it
is easier to see the branch structure.
Pruning early, though, will remove this year’s flower buds which
begin
forming right after bloom of the previous year.
Check bearded iris leaves for
yellow streaks and mushy spots in the plump surface roots called
“rhizomes”. These
are sure signs of iris borer activity. Check the rhizomes for
borer
holes
and remove infested parts. In
the future, avoid covering rhizomes with mulch or soil (this
favors borer
activity), or grow resistant Siberian
iris instead.
If you're using a string trimmer
to trim around trees, be careful not to damage the tree bark.
Repeatedly striking tree bark with weed
whacker strings opens the tree to infection, and may over time kill the
tree by
cutting through the tender bark. Technically, this is known as
“girdling”. Mulch around trees so you don't have to
trim
close to the trunk, or place tree guards on the trunks. Just make
sure
you don’t pile mulch up around
the trunks.
Young cucumber, melon, and squash
plants are easy prey for cucumber beetles. As the seedlings
grow, these yellow-striped or yellow-spotted beetles emerge to feed on
the
foliage. The beetles also spread bacterial wilt disease. To
control
them
in a small planting, cover plants with a lightweight white fabric
referred to
as a “floating row cover”, spray pyrethrum botanical
spray, or trap
them
with yellow traps coated with petroleum jelly.
With the summer weather upon us,
slugs are having a field day. They eat holes in the leaves of many
vegetable, annual, and perennial plants. There are many chemical and
non-chemical controls
for slugs, including a new one that contains iron phosphate as the
active
ingredient. The slugs eat the pellets and die, yet the iron
phosphate
doesn't harm other wildlife or the environment. There are many
other
methods to trap them, such as under boards or in wet newspaper rolls in
the
garden. The more famous trap is saucers
of beer which attract them and in which they drown. Some
gardeners
swear by coffee grounds
sprinkled around plants.
As your peony blooms fade, snip
off the dead blossoms. Removing the dead blossoms will not only make
the bush
more attractive, it will allow the plant to send more energy to the
leaves and
roots and less to producing seed. Spent
blossoms also are prone to the gray mold disease which looks just as
its name
indicates.
Keep new plantings well watered
through the summer. Many new flower varieties you may have purchased in
pots
like lots of fertilizer. If you didn’t
incorporate a slow release chemical fertilizer into planters, you can
“topdress” or sprinkle some on top. Or
use a liquid fertilizer, applied often and according to label
directions and
amounts.
(Charlie Nardozzi is a nationally known horticulturist,
author, gardening consultant, and garden coach
(CharlieNardozzi.com).
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