I live in Western PA, zone 5/6. I was told to pruned Hydrangeas in the
spring back to 6-8" from the ground. That they only bloom on old wood.
It seems to me that if you do this, any growth that year would be new
wood and no blooms. This seems to have happened to my bush. It's about
2 1/2' tall, 3' in diameter, great foliage, but no blooms.
When should it be pruned?
Different species of hydrangeas have different criteria for pruning. Some
need very little pruning at all, other than to shape, as with H.
quercifolia & H. anomala petiolaris. H. arborescens does well with the
dramatic pruning you describe. Pruning of H. paniculata would depend on if
you were training it to be upright like a tree or as a broad shrub, & need
not be dramatic pruning, just barely enough to induce new growth on which
flowers occur, though in your zone a more dramatic pruning might be needed
because of winter damage. Most hydrangeas prefer late winter pruning, but
H. macrophylla is better done in late summer when flowers are getting
scruffy & new shoots are developing; it needs a heart of old wood to
always to be preserved since it will bloom on shoots from the old wood;
late winter or spring pruning would remove buds, & in your zone as the
buds would probably freeze off.
If your instructions for yours was correct you must have H. arborescens, &
in your zone it suffers a lot of winter injury so it is recommended to
prune it to under a foot height in late winter or very early spring (such
a complete cut-back wouldn't be necessary where I live). It flowers on
NEW growth, & if yours failed to flower, probably not from degree of
pruning, unless you did it after new spring growth had started, in which
case you cut off the buds. It's not unusual that hydrangeas do not to
bloom when very young & newly planted as they expend most energy on
developing roots & settling in. Or with too much sun wit&h too little
summer watering, buds might bake so never develop. Though they like very
bright shade or dappled sunlight, too deep a shade will keep them from
blooming. Or if you fertilized the hell out of it, it'll be annoyed; it
will get bushy without flowers if over fertilized.
Someone else with more hydrangeas than I grow may have better advice, but
it'd help to know if it really is H. aborescens you're asking about,
because it makes a big difference.
-paghat the ratgirl
"Of what are you afraid, my child?" inquired the kindly teacher.
"Oh, sir! The flowers, they are wild," replied the timid creature.
Paghat's information is very good. Pruning hydrangeas of any type is never a
"requirement" and many are best just left alone to grow and flower at will,
however your climate and the specific type of hydrangea will be a big factor
in how well they do this. Both paniculata and arborescens bloom on new wood
and in colder climates, often act more like a herbaceous perennial rather
than a shrub - they can die back to the roots in winter but will regrow and
bloom the following summer. Removing the dead wood should be done in spring
as you see new growth developing.
Bigleaf hydrangeas (H. macrophylla) are marginally hardy in zone 6 and
typically not hardy in zone 5 without winter protection. These do bloom on
new wood and the new growth that developed this season must be protected
from freezing in order to enjoy any flowering. A google search will turn up
any number of sites that can give you specifics on how best to accomplish
this. I don't generally recommend that you prune these at all except to
remove old flowerheads or dead wood, unless they become excessively leggy.
Then you can cut back selected branches/stems with the understanding that
the cut stems will not produce flowers for that season.
There a couple of new macrophyllas on the market that have been developed
for exceptional cold hardiness and the ability to bloom on both new AND old
wood. Look for 'Endless Summer' or 'All Summer Beauty" - they are reputed to
be hardy to zone 4.
pam - gardengal
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