I have a very long dead leylandi hedge (and am quite beginner level in gardening knowledge!). Would love to replace it with holly which is quite pricey to buy. A friend has some woodland which has loads of self seeded holly growing in it (which she plans to eradicate) and has said I can dig up as much as I like and transplant it. Would this work or am I likely to kill the plants by digging them up? Any advice at all very much appreciated. And if it is possible what should be the maximum size I try to dig up?! Thanks!
The real issue here for me is the timescale. First of all, you need to get rid of those leylandii. This is a really big job! You need to cut them down and get rid of all the branches, then ideally (for a neat look) get rid of the stumps, then dig in loads and loads of compost and manure as the soil underneath will be knackered.
Then you can dig up the small holly trees, provided they are quite young. I wouldn't take anything too large - the bigger the bush, the bigger the rootball, the more damage is done with moving and the more it tends to suffer when shifted. Even though holly isn't very deep rooted and is therefore quite easy to shift, expect to need to put your back into it with the digging! You'll need gloves/protective clothing to handle them too, for obvious reasons. Transporting them needs consideration - bear in mind that if they are small you may need 2-4 a metre to fill a hedge.
The real problem is that if you want to do it before autumn, you need to get a move on. They should really be moved in the next couple of months at the latest, really. Dig out as much of the rootball as you can, wrap the roots tightly in plastic and plant out as soon as possible - using rootgrow (ask for it in the garden centre) can help them to establish. You may need to water really regularly throughout the summer.