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Yes, put the cuttings in the ground after loosing the dirt in the immediate area only. Do not add fertilizer at this point. The cutting must first establish its roots in the ground. Typically, trees are fertilized in early spring as growth begins. Use a long-acting granular fertilizer meant for trees. I would only fertilize for 1-2 years without getting a soil test.

A tree, or plant is considered mature when it is at the age to be able to reproduce. If you see any signs of flowering or seed/fruit production, the the tree is considered mature.

I'm sorry, we do not sell from this site. Gardening Know How is an information web site.
Try checking with your local garden centers and garden nurseries.
You can also check with Landscape companies in your area.

There are actually many good options for this purpose that will not draw wildlife to them, and they are armed with thorns! This article will give you examples: https://www.gardeningknowhow.com/ornamental/shrubs/shgen/using-defensive-shrubs.htm

"Traditional" hedgerow plants are sun loving. Under the shade of trees and with competition from tree root systems is not the best growing conditions for most plants. You may encounter problems in the long term for both the shrubs and the trees. Imposing competition for water and nutrients is usually not a good idea. With shade, competition, and combine that with alkaline soil from the chalk, the list will be greatly narrowed.

But if you are determined, and you know how to practice good soil and water management and to neutralize the alkalinity, you might find some possibilities for shade plants to suit the purpose in this listing from the Royal Horticultural Society.

You may want to take the list to a local garden center and see what is available and maybe get some tips from a local nurseryman, gardener or landscape designer.

https://www.rhs.org.uk/advice/profile?PID=430

Your hardiness zone appears to be 7a. Choose shrubs/trees that are hardy to zone 6 or colder so you won't lose them in a severe winter. Do you have overhead power lines to consider when making your choice? Do you have the funds to create a berm of soil on which to plant? You can use smaller plants on a berm. To make recommendations, it is necessary to know how much sun the area gets and if you are willing to maintain evergreens as a hedge or prefer low/no maintenance. Popular options include holly and Emerald Green arborvitae, cultivars of which comes in different ultimate heights. Visit a local nursery for advice and options available locally. There may be local ordinances on height of fences and hedges so check with your local government or HOA first.