In article , im-the-boss
wrote:

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.
-from Peter Newell's "Wild Flowers"
Visit the Garden of Paghat the Ratgirl: http://www.paghat.com