We planted crape myrtles
last spring and they flowered their first year in the ground. How
should crape myrtle be pruned, and when is the best time to prune so
we donít remove their flower buds? Should we cover them in the
winter to ensure their survival?
A. Crape myrtles (Lagerstroemia spp.) are not considered reliably
hardy for us in USDA Zones 5 and 6. There are two primary species of crape myrtles, Lagerstroemia indica and fauriei. L. indica is
reliably hardy from Zones 7 to 9, while L. fauriei is supposed to be
hardy to Zone 6. 'Hopi' and 'Zuni' are hybrids between the two
species and are reported to be hardier in northern climates.
Where you can grow Crape Myrtles
If you live in an
urban area like Pittsburgh, your chances of success are better than
if you live in the suburbs or a more rural area. Due to the
concentration of pavement and buildings, urban areas tend to absorb
and hold more heat than less built-up areas. I can think of several
crape myrtles growing well in the city of Pittsburgh.
The City of Pittsburgh Pennsylvania
Where to plant Crape Myrtle
The way you
plant and care for marginally hardy plants has a big influence on
how well they survive. Be sure they are planted in well-drained
soil; standing water around their roots through the winter is a
recipe for failure. Avoid planting them against south-facing walls.
On sunny days and during warm spells in winter, south-facing walls
absorb and then radiate heat that can cause nearby plants to break
winter dormancy. Buds that start to break, and any new growth will
be killed outright when temperatures fall back to a normal range.
Pruning & Fertilization
or fertilizing marginally hardy plants after early July because
these activities push new growth that may not harden off before
winter cold hits. Older and more established crape myrtles will fare
better than young ones when we get into severe cold snaps.
Winter protection of Crape Myrtles
As for covering them through the winter, wait until the ground
freezes, then mulch with 3 or 4 inches of shredded bark, straw,
shredded leaves or well-composted sawdust. The point is to keep the
ground frozen, which protects young plants from heaving out of the
ground during winter's freeze-and-thaw cycles. Keep the mulch
several inches away from physical contact with tree trunks. Be sure
to pull the mulch back once we are past danger of hard frost in the
spring. If your crape myrtles are exposed to strong winter winds,
you can erect a windbreak by stapling burlap or erosion control
fabric onto wooden stakes and driving them into the ground on their
Because crape myrtles produce flower buds on the
current year's growth ("bloom on new wood"), they are usually pruned
in late winter or very early spring.
Shaping Crape Myrtle plants
can be trained as single-stemmed small trees or as multistemmed
shrubs, depending on your preference. Once you have the basic
framework established, crape myrtles require only light pruning to
maintain that form. Growing them as small trees allows you to limb
them up to reveal their lovely exfoliating bark.
gardeners do not always get to enjoy the bark because crape myrtles
can be killed back to the ground during severe cold snaps. If you
want to train yours into small trees, select three to five
well-spaced shoots that grow from the ground as the main trunks and
remove the rest. Remove the side branches from your selected shoots
about halfway up their length. In subsequent years you may need to
remove additional shoots that sucker up from the base to retain the
tree shape. You can also prune any excessively long shoots growing
from the main trunks back into shape with the rest of the tree or
remove them entirely at their point of origin.
If you prefer to
grow your crape myrtles as multi-stemmed shrubs, you can cut them
back hard -- within 6 inches of the ground -- every spring. You will
never get to enjoy that exfoliating bark, but you can keep them
small. You can also prune them more moderately to allow them to grow
into larger shrubs. Prune out weak, spindly twigs to open the
interior of the plants to more sun and better air circulation. You
can also shorten long branches back into shape with the rest of the
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