Multiple books just about pruning and training of plants are in print or on library shelves. These talk about best timing for specific kinds.

Prune the roses when the forsythia blooms. Probably February in your area.

Prune the forsythia after blooming, so in spring, gives it time to set new flower buds for next year.

I've always pruned the mophead hydrangeas same time as the roses. Has always worked well for me, although every one else in the world insists that hydrangeas be pruned in summer after blooming. Mopheads bloom on new wood, as do roses. Oakleafs and peegees bloom on older wood so it makes sense to prune them later, but I've never grown those kinds.

Buddleia, ditto. I prune those same time as the roses.

Don't prune Japanese maples. No no no. It ruins them. They must grow free and unfettered or the shape is ruined. If you absolutely have to trim a branch do it in winter.

Hold on........I think that hydrangea pruning info is backwards :-) Hydrangea macrophylla, serrata and quercifolia - the mopheads, lacecapes and oakleafs - bloom on OLD wood, growth that was produced the previous season (except for a few newer intros that bloom on both old and new wood). Pruning should be limited to removing deadwood in spring and older canes to keep plant vigorous and limit size - I would never recommend routine pruning on these to maintain a smaller size. Site according to expected mature growth and leave them alone! Paniculatas ('PeeGee', etc.) and arborescens ('Annabelle') bloom on new wood and can be cut back hard each season in early spring if necessary or desired.

Lavender should be sheared lightly in early fall to remove spent flower stalks and tidy and then a closer shearing in spring to keep the plant compact and promote additional flowering.

Japanese maples are frequently pruned :-) I know of several professional pruners that specialize in just these plants. But there is a bit of an art to doing so correctly. One wants to enhance the natural growth habit and accentuate the sculptural form these trees have. Dead wood should be pruned out at any time. Conflicting branches and pruning to train or enhance growth are best accomplished before the sap starts rising in late winter - December/January. Thinning of the canopy is best accomplished while the tree is in leaf - early summer (June) is suggested.

There are various reasons lilacs fail to bloom. One factor can be the maturity of the plant but you may want to research to see what other reasons may contribute and be a factor in your situation.

And I agree with bboy that seeking out a good pruning guide would be a big help. There are just so many variables regarding what to prune when and the proper technique and checking online really does not always provide good info :-) I really like the AHS Guide to Pruning and Training by Christopher Brickell. Very thorough, easy to follow and with excellent illustrations. Most bookstores and garden centers carry it or try Amazon. And many larger retail nurseries offer pruning classes from time to time - take advantage of any you can find. Hands-on application and experience is far more informative than reading books

Gardengal are any of your Japanese maple pruning friends in Portland?

My friend asked me yesterday day why her mophead hydrangea hasn't bloomed in three years. Turns out her sister has been chopping it down every year because she didn't like looking at bare stems in winter.....She didn't prune it when it was smaller but since it has reached mature height she has been cutting off all the blooms.

Unfortunately not......and I'm not sure one would find it cost effective to import them for that purpose :-) Check at the Chinese garden or Hoyt Arboretum for possible referrals or at one of the better garden centers that carries a big selection of Japanese maples.