On Mon, 21 May 2012 17:20:53 +0000, hels_bells wrote:

The hedge has grown a little bit in some places and quite a lot in
others but I fear we may have a disaster on our hands as it has never
been clipped back and has an enormous amount of weeds around it which
are no doubt stifiling its growth.

I'm not sure what spirals are (tree wrap, perhaps?), but here's what I'd do:

1) trim the hedge carefully (not just whack it into a geometric shape, but
look at what you might be able to do to get the neighboring plants to
fill in for an undersized one if the gappiness continues.)

2) Figure out what weeds you have and what you'll have to do to get rid of them,then do so. I'd try to use a light-occlusive mulch myself, but some
weeds are nasty enough that I'd break out a selectively applied herbicide just
for them. If you're using light-occlusive mulch (my favorite is corrugated
cardboard with something decorative over the top), then cut the weeds down to
ground level before applying the mulch. Watch for weed regrowth, and knock it
back ASAP -- a weekly tour of the planting with hoe in hand would be a good
idea.

3) If your plants have bare legs and they shouldn't, pull the lower branches
out and peg them down to improve the shape of the bottom of the hedge.
You may also want to propagate some clippings in case you need to fill in.

I'm in the US, so hesitate to give advice about when and how hard to prune,
but I know there are excellent books on formal hedges and on pruning available
in the UK. Study the pruning manuals carefully as to where and how
to cut to persuade the plant to grow in the shape you are hoping for.
Never remove more than 30% of the plant's top growth in a year, unless you're
willing to accept that the plant may die -- I usually go for no more than
20% pruning as a rule of thumb.

In general, removing the tips of branches encourages dormant buds to sprout
lower on the plant, making the plant "bushier". Some species will respond
to pruning in this manner by new growth only closest to the pruning site,
while others will develop new branches much farther down. Without knowing
the species in your hedge, I can't guess.

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Personally, I am not a fan of nicely trimmed, single species hedges. They're
a lot of work, they're not much use for wildlife habitat, and one of the plants
in the hedge (inevitably!) doesn't grow as well, or grows too well, and
it looks gap-toothed. On the other hand, you can mix together several
different species in a meandered border and even if you lose a few or you
don't do anything to them for several years, it'll still look fine.