I know you'll get intelligent answers here, but not from me. I would like to suggest you try you tube's Plant Amnesty series which addresses pruning techinques for scores of shrubs and plants. You can see if they have one on barberrys. But also look at the introductory videos where the difference between a heading cut (just cutting straight across) and 'selective cutting' are illustrated. I gave my barberry a permanent bad hair day by using heading cuts. It really ruined the form.

based on the pic provided.. here is my suggestion:

???

i have no clue why you would 'top' a pillar plant???

https://www.google.com/search?q=Barberry+Golden+Glow+Pillar&source=lnms&tbm=isch&sa=X&ved=0CAgQ_AUoAmoVChMIpp29yoe4xwIVkxCSCh39WwmE&biw=923&bih=745&dpr=0.9

that said.. its your plant.. go at it.. if thats what you want ... why do you need our permission ...

ken

I wouldn't consider 'sudden new growth' a problem. It just shows that your shrub has got now itself settled in and the roots are starting to do their work. Personally, I would leave such a young plant well alone for a year at the very least. It needs a chance to start to show its true nature. At the moment it's a baby and we know babies can be odd shapes ;-)

Lynn, Ken *grows* on you after a while.

Sorry there wasn't something more specific to help. However, did you look at the Halls of Horticultural Horrors aka The Pruning Hall of Shame.?

Mine was Crimson Pygmy which is round, globular whatever. I didn't prune out a bit of old wood regularly. After I trimmed "back" (instead of thinning out) woody branches these branches sent out a few or more new twigs from each cut. The shrub had 'spit ends.'

I think I know what I'd do differently (cut slower, cut less, learn when in the growing season to prune) but I still don;t know the finer points of pruning various types of trees and shrubs.

I was curious and googled pruning Helmond's Pillar which is a similar shape to yours. Most of the resources said 'doesn't need pruning' and this one sentence:

"Remove any floppy or unruly shoots from fastigiate berberis, such as 'Helmond Pillar', to preserve shape. You can prune other varieties after flowering"

The two people I know who grow H's Pillar discretely tie it up with twine: one in the winter to keep it from splaying the other all the time because it is planted in too much shade and grows loosely.

Just curious, Have you checked to see if it is on your state's invasive plants list.?

I love the plant, but it has become a problem in open woodlands in Mass.

More than likely yours is Sunjoy Gold Pillar (or something similar like Golden Rocket). If you prune it in the spring by cutting it level at around 12-15" there will be a proliferation of new stems that come up and help support the vertical growth habit. If you choose to leave as is it will stay somewhat upright but many of the stems will end up leaning in time and then will send smaller vertical shoots off of themselves. In several years if it becomes too large or unkempt you can hack it off nearly at the ground to rejuvenate the entire plant.

I would not prune right now as it might encourage more growth this late in the season. Wait until spring.

thanks so much...yes, I'm pretty sure that's what I have Sunjoy Gold Pillar! ;-)

Evergreen, if flowering between winter and early summer on previous or current year's growth: trim or lightly cut back shoots after flowering. Remove dead or damaged growth in midspring. Prune annually after flowering.

Deciduous, flowering in spring or early summer on previous years' growth: cut back flowered shoots to strong buds or young lower or basal growth. On established plants, cut back about 1/3 to 1/5 of old shoots to the base to promote replacement growth. Prune annually after flowering.

(from American Horticultural Society)

thanks. when you refer to 'flowering' I assume you simply mean leafy growth? I'm not aware that this plant has what are considered 'flowers'?

No, adaorand means flowering. Berberis most certainly do flower, although many have been bred mainly for leaf colour. Google up some images and you'll see that some species and cultivars are quite showy when in bloom.

All plants flower - that's how they reproduce - but the flowers may be very insignificant or unnoticeable or they may not resemble "flowers" as most folks consider them.

Japanese barberry, Berberis thunbergii, is most often grown for its foliage effect but it does flower and produce seed, hence the invasive issues in some parts of the country. Barberry flowers tend to be yellow or orange and quite small so likely not at all noticeable on a yellow leaved shrub.