[willowman]

Can anybody tell me the best time to -

1. Have my large willow tree pollarded

2. cut back my large leylandii hedge.

Many thanks.

[Swing Swang]

With respect to point 2, doesn't matter when you cut them back if you're only going to leave a 2" stump 

[amc]

Willow will be best pollarded after leaf fall thru til mid March. amc

[tode]

We have large willows at the bottom of the garden, damp conditions, and theyve really turned into monsters. If you want to slow them down a bit, cut when in leaf. Otherwise, as amc says.
Are they growing near water?

[willowman]

swing swang - understand where you're coming from, but here in the fens they are a great windbreak to protect the garden, plus we have a business in the back garden and they are a good security fence. i've made sure they are only about 3metres tall.

tode - it isn't by water, but again, being in the Fens the water table is very high so it gets well fed. Will have a professional haircut job done during the winter, which should also give us plenty of fuel for the fire next year.

[Kristen]

You can't cut Leylandii "branches" back to old wood, they won't re-sprout.

You can "top" the trees themselves, as they will sprout from the cut top.

If its the sides you want to get back under control one option is to turn it into an along-side hedge - hard to describe, but some photos on my blog : Reviving a Leylandii Hedge

[tode]

If youve got a fireplace, then def cut in winter.
Ask em to cut at the right length for the fire 

[Bombers]

If youve got a fireplace, then def cut in winter.
Ask em to cut at the right length for the fire 

[tam]

March and sept for conifers.

[Rangerkris]

AMC is right about pollarding any tree do it whilst sap is down in the root system and you will be fine,  i did cut down some sycamore late on purpose to try and kill it but no it still put out new shoots.

[Spana]

You can't cut Leylandii "branches" back to old wood, they won't re-sprout.

You can "top" the trees themselves, as they will sprout from the cut top.

If its the sides you want to get back under control one option is to turn it into an along-side hedge - hard to describe, but some photos on my blog : Reviving a Leylandii Hedge

That looks a skilled job Kristen, and excellent result

[sunshineband]

We cut our leylanddi (windbreak for playgrounds) in March/end of April and end of August ie right now, to match in with the children not being around at the time.

Worked OK for years and they are thick and healthy, maintained at 2. - 2.5 m height, rejuvenated from 8m tall some years ago 

[tam]

Our neighbours kindly cut one side off our hedge for us and killed the lot so do be careful with drastic haircuts.

[Salmo]

You can cut the top of leylandii at any time.

Trim leylandii once a year in August. That gives time for some new growth before winter.

[Kristen]

If memory serves me, I read somewhere not to cut them too late in the Autumn because it increases the risk of the Cypress Aphid damaging the plants.  Sorry, can't find a link to corroborate