Welcome to GC Blade. I'm glad to hear how far the Leylandii are from any property. I presume you are aware of the damage they can do? I've had my drains and foundations damaged by the roots of these trees twice from a neighbours hedge. Thankfully, they had the sense to remove it last year after our second bout. Also possibly, because our insurance company was about to start chasing them for the damage. The pictures are before and after shots, they were just 15 feet away from my bungalow and were 15 feet high.
When i was looking for what to plant there , i came across a lot of hysteria surrounding this tree which made me laugh , it obviously has profound effects on gardeners . As i say i just want to know how to thicken it up , they are a bit sparse at moment , but been advised to prune them litte and often and not lop the tops until they reach desired height free the leylandii 8 PS Sheal , that is what i,m trying to achive but better kept
Native eh? How does that work then? In an urban area you want to plant trees that grew in the country before there were urban areas and expect them to survive the pollution, reduced water available to the soil, and a host of other things that man has altered over the millennia ... Native is a romance that is is rarely the simple answer that people would like it to be.
Without pointing any fingers at anyone in particular (notwithstanding that I've choose to quote your message) I think people were jumping the gun assuming this was a boundary between two properties. The O/P has described that that is not the case. I hate Leylandii, I think its a thug, but there are plenty of beautifully clipped examples around here, and anyone buying it having done some research is OK in my book.
Don't take my views as gospel, but I would suggest: When the sides are approaching the width that you want start lightly trimming them, and then as they reach full-width they will already be "under control" - i.e. they won't have a shape like ) ) ) where each bush has adopted a round shape, you will already have flattened the curved bits off, and the gaps in the middle will have been able to grow out to meet them giving you a straight finish. Trimming off the bits where it is already [nearly] wide enough will allow the plant to divert energy to the areas where you want it to grow out more. Plan to taper the hedge wider at the bottom, narrower at the top, so that it gets light all the way up, rather than having vertical sides. (So called "batter" I think) Do NOT cut the top at all until it is at least 1' past the eventual height that you want. Then cut it to, say, 6" below the height you want, and then all the soft sprouts that grow from the cut growing point can be cut at final-height making a nice flat top. Feed it with Nitrogen to make it grow. You need to be careful not to provide too much, but providing it at a time just before its Spring growth spurt is ideal - that will cause the new growth to "stretch" and then fill out, which will make it grow faster. Do not feed after, say, first week of August so that any new growth then has time to harden up before the winter. You need to water it too, I would recommend installing a leak-yhose along the length of the hedge, and running that once a week in normal weather and twice a week in really try weather. Put a flat dish about 12" wide under the leaky pipe and time how long it takes to get an inch of water in it. I would think that you need to provide about 1-2" of water at each watering. A really good deep watering, less often, is much MUCH better than little-and-often. Mulch the plants - rotted farm yard manure, or compost or similar. That will improve the soil, and keep the moisture in (put that OVER the leaky hose). Don't allow any grass / weeds to grow within 4' of the base (either side), or 2' is you are restricted by something else. That will stop competition from weeds etc. Your mulch should cover the full width of the bare area you maintain along the hedge row. However, the best thing you could have done (and maybe / hopefully did) was in the preparation before planting. A trench dug 4' wide, incorporating plenty of rotted manure / compost and double-dug to a depth of 24" - 36" would make a significant difference to the speed with which the plants get established. If they were just "plonked into holes in unprepared ground" that will, I'm afraid, several restrict the rate at which they will get established. Next up think about how you will manage a 5M hedge. Its pretty tricky cutting the top of a hedge that is that tall. I use a scaffolding tower for my tall hedges, but I only cut them once a year as it is a slow job moving the tower along the hedge - depends how long your hedge is of course There are some very stable three-legged-step-ladders - looking like a normal ladder, but with a single stay-leg at the back - which professionals use for cutting hedges, and you might like to invest in one of those. You can also get hedge-cutter attachments for brush-cutters which will give you probably 4M reach, but I don't think you are going to get up to 5M standing on the ground. Also, watch out for advice on not cutting Leylandii late in the season, they are reported to be more susceptible to attack by the Cupressus Aphid if clipped late in the season. Either way its something you should read up on as Cupressus Aphid is decimating Leylandii hedges around the country. Personally, I think you should have planted Thuja plicata atrovirens instead as it is much less of a "thug", easier to manage, and very nearly as fast growing as Leylandii, but good luck with screening the eyesore next door.
