Many gardeners are tempted to prune in the garden in the fall as a complement to the general leaf drop cleanup and preparation of the garden for winter. Tidy, tidy, tidy. But with the limited exception of certain herbaceous perennials, this is generally not a good time to prune your trees, shrubs & vines. Here's why: pruning always encourages the plant to repair the cut, i.e., to grow, but deciduous plants are not supposed to grow now. Rather they are to harden off, store carbohydrates in their roots, drop leaves and go dormant. Quit. You prune and you make them wake up and go back to work to repair the injury just when they thought it was time for the long winter's nap. As always, there are some exceptions. The main one is to remove dead or badly diseased stems as you identify them. Dead is dead and cutting off dead (as long as you don't cut back into live growth) will cause no rally by the plant to repair the dead zone. It already has quarantined it, turned it brown and in time will shed that branch or limb even if you don't cut it off.

Pruning in winter is much more acceptable for certain woody plants. By winter I mean the time when the object of your pruners, lopper or saw is fully dormant. Again dead, diseased or damaged parts can be removed. Trees that "bleed" if pruned during spring or summer -- most maples and yellowwood -- should be cut in late summer or autumn.


Pruning Hydrangeas

Pruning Hydrangea macrophylla is always a matter of concern for gardeners. Most of this species bloom only on old wood (growth from last year) so too little is preferable to too much.  A few varieties have been identified as also being capable of blooming on new wood (growth from the current year). The best way to prune is to thin older plants (4+ years) by cutting out a portion (say, one-third) of the old woody canes to the base (see photo below right) as well as any dead wood in late winter before the new buds begin to swell. To check to see if a dormant stem is alive or dead, nick the bark away slightly and look at the color beneath.  If it's green (as in photo below left) the stem is alive.  If it nicks to reveal brown, it's dead at that point along the stem.  Nick it again lower on the stem.  If it is always brown you should remove it all the way to the base.



Do not prune by shortening stems, except to remove old flowerheads, as you are likely to cut off your flowerbuds.  We think it is best to leave the dried heads of old blooms on the plant until winter's end to help protect new flowerbuds.  When danger of late frost is past, carefully deadhead old blooms by cutting off above the first pair of vigorous new buds. 

A young plant may be cut back in June/July to enhance its structure or fullness and this should not harm next year's bloom. Likewise, if you need to rejuvenate an overgrown, tired, or non-blooming older macrophylla, you should do this corrective pruning, shaping and thinning smack in the middle of mid-summer for the same reason: your shrub will have the maximum time to produce new branches and harden off before the first fall freezes. 

Likewise, do not prune oakleaf (Hydrangea quercifolia) in fall or at the end of winter since they also bloom on old wood. 

You can prune the PG types (Hyd. paniculata varieties -- e.g. 'Limelight', 'Tardiva', 'Phantom', etc.) & our native species (Hyd. arborescens 'Annabelle', "Incrediball", 'Bounty', etc.) at the end of winter if you wish, because they bloom on new growth.

 

Some other plants that can benefit from a pruning before spring growth begins, depending on their age and condition, are: Abelia (Abelia sp.), Indigo (Indigofera sp.), the summer blooming spireas (Spiraea japonica and S. x bumalda), Butterfly Bush (Buddleia sp.), Arkansas Blue Star (Amsonia), American Beautyberry (Callicarpa americana), Chaste Tree (Vitex). If you are growing shrubs like Ninebark (Physocarpus) primarily for their intense foliar color (purple or gold) rather than their flowers, they too can be pruned in early spring to promote lush new growth (at the expense of this season's flowers).

Gene Griffith and Elizabeth Dean
Wilkerson Mill Gardens
9595 Wilkerson Mill Rd.
Palmetto, Ga 30268
(770)463-2400
(770)463-9717 fax
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