Prune for natural shape

No matter how you cut it, you can't eliminate plant's natural form


Dwarf burning bush  (Euonymus alata 'Compacta', shown above) is dense twiggy and boxy when repeatedly sheared but will return to full size and shape if left alone. Look below to see the same species full grown and unpruned.

Best approach: The sheared shrub will usually re-acquire its inborn shape most quickly if you cut it back to main canes. Otherwise, allow it several years to gradually lose all those shearing-induced extra branches.

Hello, you two!

In What's Coming Up 80 you say the simplest pruning is enhancing natural shape. What if a bush has been pruned to another shape for a long time? Can I get the natural shape back?

I bought this house late last summer and didn't do much to the outside yet. There is a little hedge, I think it's boxwood but who knows, it's just a flat topped square sided line that has probably more branches than leaves right now. There's room for it to be wider because I think the former owners grew flowers all along there every year and I don't need that.

Also, there are some bigger bushes that a friend has guessed are a Viburnum of some sort. They've been cut to about five feet tall and wide, kind of ball shaped.

Their lower half is pretty bare. They're pretty dense along the top and the upper sides, like they have a "skin" of criss crossing twigs a few inches deep. Inside the twigs there are just a few grayish widely spaced branches that go straight up from the ground.

Suggestions are appreciated. I've gotten the idea in your newsletters that late winter and early spring are times to prune. I'm itching to do something with these bushes. - T.M. -

Lots of plants mature as round or mounded forms about as wide as they are tall. Here are two in their natural mounded form. Above, unclipped evergreen boxwood (Buxus sempervirens) 'Vardar Valley' and (below) Japanese holly (Ilex crenata) are both quite round. They also mimic each other in leaf and branching so similar we understand the comment "I think it's boxwood but who knows".

Read more about Tree- and shrub shapes.

Read on for tips on identifying a woody plant even when it's leafless in Winter twig tree ID.

Hands off or hard cut

Yes, T.M. Such plants can resume their natural shapes.

Take your pick of paths:
1) If there is room for the plants to expand, you can simply stop cutting them, or,
2) Cut them back hard so they can start over.

The trouble with path number 1 in this case is that you don't know what species and variety these are. Without that you don't know their potential size to decide if you do have adequate space.

The second path is our choice most of the time since it allows for a quicker return to natural grace. Even if the plants are ultimately too large for the space they can be allowed to grow back in their natural shapes and afterward be kept small with pruning every year or two.

How long it takes to grow out depends on:
• Its species' growth rate,
• Whether it's well sited, for light and water,
• Whether it's healthy or weak, and
• Whether you decide to help.

Slow growth, look away for a year or three

Take a plant with a slow growth rate, maybe four inches a year. If you just stand back and let them grow starting from that much-branched outer layer a few inches deep, it may be three years or more before any new growth extends far enough beyond the rest for chemical dominance to kick in. Once some growth gets ahead of the pack, those furthest-out tips start "telling" the followers how to grow. Over the next years lesser twigs will wane and leading tips will fill out with side branches. Until then, the shrub or tree may look like a bad haircut -- unkempt bits jutting from a still-discernible old edge.

Restrain yourself during this grow-back period. Read more about why, and what you'll see, in What's Coming Up 183 in the article Hold those clippers: Let ungainly evergreen grow back out (Clipped ungainly evergreen).

Speedy species, cut hard and step back

Then there are plants with faster growth rates, over a foot per year. Most that are pruned hard probably fall into this category, assigned there because at some point their owners said, "Whoa, that bush is just not going to stop growing!"  or "Man, that thing looks wild!" Most Viburnums are in this category. If they are healthy Viburnum and its new canes may grow 3 feet or more in one season, slowing down a bit in year two as those straight new canes develop side branches.

So a fast growing shrub or tree can resume normal operations in just a year or two. However, if you simply let it grow out from its formerly-clipped outline it's likely to appear wilder during its transition. Its emerging tips will protrude a foot or more, looking like antennae bristling from a satellite until side branches develop and slow the race.

Helping the comeback

Sounds like you're willing to give these plants a chance. To help them, two thoughts:

1) You can boost the plant's vigor. Do that by loosening the soil in and just beyond its root zone, adding some slow release fertilizer and mulch, then making sure that space is kept moist.

2) You can prune to thin out some* of the artificially-branched tips to speed the rightful leaders' resumption of power.  *"Some" can be "all." For more, read Grow back or go away pruning.

Just look at what a speedy species can do. This Forsythia was cut to the ground immediately after bloom in May...

... but you can't tell by looking at it three weeks- and 6 weeks later!