To make a really good intruder proof hedge use prickly shrubs that have a dense growth habit and will form a barrier all year round. Rosa rugosa can make a very prickly hedge but this can also make it really nasty to prune. It is vigorous and fast growing, so many people deal with the pruning issue by simply cutting it back to ground level each year, however this would leave the garden open to intruders. Roses are also quite greedy plants and there is the risk that they might compete with vegetable crops for nutrients.There are better alternatives. Hawthorn (Crataegus monogyna) and blackthorn (Prunus spinosa) make lovely prickly barriers of deciduous native hedging, that really knit together with time. Both are also excellent for attracting wildlife, offering spring flowers, autumn berries and excellent nesting cover.If an evergreen hedge is preferred consider pyracantha or holly Ilex aquifolium). Pyracantha makes a good thorny barrier, and the flowers and berries provide lots of interest throughout the year, attracting wildlife. Choose a variety from the Saphyr range as these have better resistance to fireblight. Holly makes a nice formal barrier with time, although it is quite slow to establish. It is more expensive to buy as it is not possible to purchase as bareroot. If choosing holly, then select a self fertile variety such as J.C. van Tol or pick a female variety and plant just a few males in between to ensure lots of berries.