Timelines for trimming

When to cut? How long before it looks like we want it to?

There is so much advice about when to prune, offering so many scenarios, it can make a head spin. Rather than get caught in that whirl, look at it from an overall perspective and you should see:

So many people cut at so many times that there's only one certainty:
There is no "best" time,
only many options.
- Janet -

Sometimes we knock ourselves out to cut at a time most likely to elicit the response we need. At other times we've been forced to cut on schedules we feared disastrous.  Based on what we've done over 30 years and what we have seen plants do in response, we think there's worth in all times, all of the guidelines below. Some overlap, others are contradictory or mutually exclusive but every one can apply. None of them should ever stop you from cutting when you need to!

Choosing a date to make a cut.

There are great times and good times to prune, and only a few to avoid. The following applicable statements are in order as they crop up on a calendar:

  • Late November - early March:
    Prune while the plant is dormant and the buds set for the year's growth, to best control upcoming growth.DSC_5006.jpg
  • Prune during winter thaws. Overcast days just above freezing are great. Avoid pruning hard enough to bare interior wood if the temperature is likely to plunge suddenly at sunset.
  • After the spring equinox:
    Prune just before budbreak if the cut is drastic and bareness might be objectionable -- there will be minimal bare time.
  • DSC_7285.jpgAvoid pruning when the leaves are forming or falling. In spring during most active growth and in fall as leaves drop, the plant's ability to seal over pruning wounds is not so good as at others times.
  • May, early June:
    Prune when that season's shoots are new, to promote density.
  • To control shape, avoid pruning during periods of active growth (spring when shoots expand; fall when roots are growing rapidly)
  • Prune right after bloom as a general hedge against reducing the next year's flowering.
  • Late July, August, early September:
    Prune after the season's growth is hardened off and buds are set for next spring, if you want the plant to keep its just-clipped look for the longest possible stretch. So August or early September are good times to trim hedges, topiary and others that look best with a sharply defined edge.
  • If the plant is a bleeder -- produces heavy running sap from wounds -- and that bothers you, prune in late summer or during a winter thaw.
  • Prune shortly after the season's growth has set if you want to curtail the plant's energy and subsequent growth, such as when you want to keep a plant smaller than its potential.
  • October, November:
    Avoid pruning when leaves are forming or falling.

Drastic and gradual timelines

You can ease a plant into a new size or shape, or you can hurry it through the transition.

  • To cut all at once, just do it. Whenever!
  • For a gradual change (over 3-4 years), decide which branches you will keep over the long haul and remove the others a few at a time. This allows the plant to keep most of its energy and makes it less likely that prodigious sucker growth will occur that then requires thinning.
  • You can cut deeply into one side of a hedge this year, the other side next year, if you want to retain the hedge's presence but rejuvenate it. If you follow this schedule and the hedge ahs a north side and a south side, cut the sunny side first so light penetrates to the shadier surfaces.
  • If a plant is in tough shape, improve its growing conditions and overall health before making drastic cuts. If the cuts you plan are drastic, make one at a time, not making the next until you see the plant respond with vigorous new shoots.
  • Some plants do not sprout from bare wood (juniper, arborvitae, pine, spruce, falsecypress) so make every drastic cut to just above a leafy/needled tip or remove the entire branch.

Examples of what we prune, when

Some of the plants we prune, why we prune them and when we try to do that pruning:

  • Trees we are keeping small but wish to look like trees, not bushes: Late summer.
  • Fruit trees. Also "bleeders" such as maples, birch and beech: Winter thaw.
  • Trees at risk of disease spread by insects (oaks vs. oak wilt): Prune between the time killing frost comes in late fall and budbreak in spring.
  • Summer bloomers such as butterfly bush (Buddleia davidii), panicle hydrangea (H. paniculata), Franklin tree (Franklinia alatamaha), rose of Sharon (Hibiscus syriacus), blue mist spirea (Caryopteris x clandonensis): Just before budbreak.
  • Shrubs/Trees we're growing for foliage effect or for colorful new stems, such as smoke bush (Cotinus), redtwig dogwood, golden vicary privet, barberry: Just before budbreak in spring.
  • Woody plants we are cutting back hard to start over again, which may be just about everything: Just before budbreak.
  • Pines and spruces we are fattening up: While new growth is soft "candles."
  • Early spring bloomers we want to keep small (forsythia, flowering almond, lilac, cherry): Right after flowering finishes.
  • Hedges and topiary: Late summer.
  • Shrubs pruned to look like trees, and trees kept looking like small versions of their potential selves (Such as shrubs grafted to a standard -- a single trunk, Japanese maples: Late summer or during a winter thaw.
  • For a detailed list of which shrubs to prune when and also how, see What's Coming Up Issue 86.

In summary: The million-cut answer

We once queried Ralph Shugert about pruning. Shugert was then chief horticulturist at Zelenka Nursery, presiding over production of a million yews and many other popular foundation plants.

"When can we cut back a yew?" We asked.

"Any time." Was his answer.

"Even if we're cutting 'way back..."

"Any time" he said, again, not even waiting for the end of the question.

"But is there a best time? When do you cut your yews in the field?"

We cut when we have the time. Buyers like them bushy so it's great if we can promote bushiness by cutting when the new growth is soft. But we have a lot of cutting to do so we do it whenever.
- Ralph Shugert -